of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
/*
|
|
|
|
* Device tree helpers for DMA request / controller
|
|
|
|
*
|
|
|
|
* Based on of_gpio.c
|
|
|
|
*
|
|
|
|
* Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
|
|
|
|
*
|
|
|
|
* This program is free software; you can redistribute it and/or modify
|
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|
|
* it under the terms of the GNU General Public License version 2 as
|
|
|
|
* published by the Free Software Foundation.
|
|
|
|
*/
|
|
|
|
|
|
|
|
#include <linux/device.h>
|
|
|
|
#include <linux/err.h>
|
|
|
|
#include <linux/module.h>
|
2013-04-19 16:42:14 +07:00
|
|
|
#include <linux/mutex.h>
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
#include <linux/slab.h>
|
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|
|
#include <linux/of.h>
|
|
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|
#include <linux/of_dma.h>
|
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|
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|
|
|
|
static LIST_HEAD(of_dma_list);
|
2013-04-19 16:42:14 +07:00
|
|
|
static DEFINE_MUTEX(of_dma_lock);
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
|
|
|
/**
|
2013-04-19 16:42:14 +07:00
|
|
|
* of_dma_find_controller - Get a DMA controller in DT DMA helpers list
|
2012-10-12 02:43:01 +07:00
|
|
|
* @dma_spec: pointer to DMA specifier as found in the device tree
|
|
|
|
*
|
|
|
|
* Finds a DMA controller with matching device node and number for dma cells
|
2013-04-19 16:42:14 +07:00
|
|
|
* in a list of registered DMA controllers. If a match is found a valid pointer
|
|
|
|
* to the DMA data stored is retuned. A NULL pointer is returned if no match is
|
|
|
|
* found.
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
*/
|
2013-04-19 16:42:14 +07:00
|
|
|
static struct of_dma *of_dma_find_controller(struct of_phandle_args *dma_spec)
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
{
|
|
|
|
struct of_dma *ofdma;
|
|
|
|
|
2012-10-12 02:43:01 +07:00
|
|
|
list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
|
2013-04-22 15:33:33 +07:00
|
|
|
if (ofdma->of_node == dma_spec->np)
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
return ofdma;
|
2012-10-12 02:43:01 +07:00
|
|
|
|
2017-07-19 04:42:58 +07:00
|
|
|
pr_debug("%s: can't find DMA controller %pOF\n", __func__,
|
|
|
|
dma_spec->np);
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
|
|
|
return NULL;
|
|
|
|
}
|
|
|
|
|
2015-04-09 16:35:47 +07:00
|
|
|
/**
|
|
|
|
* of_dma_router_xlate - translation function for router devices
|
|
|
|
* @dma_spec: pointer to DMA specifier as found in the device tree
|
|
|
|
* @of_dma: pointer to DMA controller data (router information)
|
|
|
|
*
|
|
|
|
* The function creates new dma_spec to be passed to the router driver's
|
|
|
|
* of_dma_route_allocate() function to prepare a dma_spec which will be used
|
|
|
|
* to request channel from the real DMA controller.
|
|
|
|
*/
|
|
|
|
static struct dma_chan *of_dma_router_xlate(struct of_phandle_args *dma_spec,
|
|
|
|
struct of_dma *ofdma)
|
|
|
|
{
|
|
|
|
struct dma_chan *chan;
|
|
|
|
struct of_dma *ofdma_target;
|
|
|
|
struct of_phandle_args dma_spec_target;
|
|
|
|
void *route_data;
|
|
|
|
|
|
|
|
/* translate the request for the real DMA controller */
|
|
|
|
memcpy(&dma_spec_target, dma_spec, sizeof(dma_spec_target));
|
|
|
|
route_data = ofdma->of_dma_route_allocate(&dma_spec_target, ofdma);
|
|
|
|
if (IS_ERR(route_data))
|
|
|
|
return NULL;
|
|
|
|
|
|
|
|
ofdma_target = of_dma_find_controller(&dma_spec_target);
|
|
|
|
if (!ofdma_target)
|
|
|
|
return NULL;
|
|
|
|
|
|
|
|
chan = ofdma_target->of_dma_xlate(&dma_spec_target, ofdma_target);
|
|
|
|
if (chan) {
|
|
|
|
chan->router = ofdma->dma_router;
|
|
|
|
chan->route_data = route_data;
|
|
|
|
} else {
|
|
|
|
ofdma->dma_router->route_free(ofdma->dma_router->dev,
|
|
|
|
route_data);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Need to put the node back since the ofdma->of_dma_route_allocate
|
|
|
|
* has taken it for generating the new, translated dma_spec
|
|
|
|
*/
|
|
|
|
of_node_put(dma_spec_target.np);
|
|
|
|
return chan;
|
|
|
|
}
|
|
|
|
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
/**
|
|
|
|
* of_dma_controller_register - Register a DMA controller to DT DMA helpers
|
|
|
|
* @np: device node of DMA controller
|
|
|
|
* @of_dma_xlate: translation function which converts a phandle
|
|
|
|
* arguments list into a dma_chan structure
|
|
|
|
* @data pointer to controller specific data to be used by
|
|
|
|
* translation function
|
|
|
|
*
|
|
|
|
* Returns 0 on success or appropriate errno value on error.
|
|
|
|
*
|
|
|
|
* Allocated memory should be freed with appropriate of_dma_controller_free()
|
|
|
|
* call.
|
|
|
|
*/
|
|
|
|
int of_dma_controller_register(struct device_node *np,
|
|
|
|
struct dma_chan *(*of_dma_xlate)
|
|
|
|
(struct of_phandle_args *, struct of_dma *),
|
|
|
|
void *data)
|
|
|
|
{
|
|
|
|
struct of_dma *ofdma;
|
|
|
|
|
|
|
|
if (!np || !of_dma_xlate) {
|
|
|
|
pr_err("%s: not enough information provided\n", __func__);
|
|
|
|
return -EINVAL;
|
|
|
|
}
|
|
|
|
|
|
|
|
ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
|
|
|
|
if (!ofdma)
|
|
|
|
return -ENOMEM;
|
|
|
|
|
|
|
|
ofdma->of_node = np;
|
|
|
|
ofdma->of_dma_xlate = of_dma_xlate;
|
|
|
|
ofdma->of_dma_data = data;
|
|
|
|
|
|
|
|
/* Now queue of_dma controller structure in list */
|
2013-04-19 16:42:14 +07:00
|
|
|
mutex_lock(&of_dma_lock);
|
2012-10-12 02:43:01 +07:00
|
|
|
list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
|
2013-04-19 16:42:14 +07:00
|
|
|
mutex_unlock(&of_dma_lock);
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(of_dma_controller_register);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* of_dma_controller_free - Remove a DMA controller from DT DMA helpers list
|
|
|
|
* @np: device node of DMA controller
|
|
|
|
*
|
|
|
|
* Memory allocated by of_dma_controller_register() is freed here.
|
|
|
|
*/
|
2013-04-19 16:42:14 +07:00
|
|
|
void of_dma_controller_free(struct device_node *np)
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
{
|
|
|
|
struct of_dma *ofdma;
|
|
|
|
|
2013-04-19 16:42:14 +07:00
|
|
|
mutex_lock(&of_dma_lock);
|
2012-10-12 02:43:01 +07:00
|
|
|
|
|
|
|
list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
|
|
|
|
if (ofdma->of_node == np) {
|
|
|
|
list_del(&ofdma->of_dma_controllers);
|
|
|
|
kfree(ofdma);
|
2013-04-19 16:42:14 +07:00
|
|
|
break;
|
2012-10-12 02:43:01 +07:00
|
|
|
}
|
|
|
|
|
2013-04-19 16:42:14 +07:00
|
|
|
mutex_unlock(&of_dma_lock);
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(of_dma_controller_free);
|
|
|
|
|
2015-04-09 16:35:47 +07:00
|
|
|
/**
|
|
|
|
* of_dma_router_register - Register a DMA router to DT DMA helpers as a
|
|
|
|
* controller
|
|
|
|
* @np: device node of DMA router
|
|
|
|
* @of_dma_route_allocate: setup function for the router which need to
|
|
|
|
* modify the dma_spec for the DMA controller to
|
|
|
|
* use and to set up the requested route.
|
|
|
|
* @dma_router: pointer to dma_router structure to be used when
|
|
|
|
* the route need to be free up.
|
|
|
|
*
|
|
|
|
* Returns 0 on success or appropriate errno value on error.
|
|
|
|
*
|
|
|
|
* Allocated memory should be freed with appropriate of_dma_controller_free()
|
|
|
|
* call.
|
|
|
|
*/
|
|
|
|
int of_dma_router_register(struct device_node *np,
|
|
|
|
void *(*of_dma_route_allocate)
|
|
|
|
(struct of_phandle_args *, struct of_dma *),
|
|
|
|
struct dma_router *dma_router)
|
|
|
|
{
|
|
|
|
struct of_dma *ofdma;
|
|
|
|
|
|
|
|
if (!np || !of_dma_route_allocate || !dma_router) {
|
|
|
|
pr_err("%s: not enough information provided\n", __func__);
|
|
|
|
return -EINVAL;
|
|
|
|
}
|
|
|
|
|
|
|
|
ofdma = kzalloc(sizeof(*ofdma), GFP_KERNEL);
|
|
|
|
if (!ofdma)
|
|
|
|
return -ENOMEM;
|
|
|
|
|
|
|
|
ofdma->of_node = np;
|
|
|
|
ofdma->of_dma_xlate = of_dma_router_xlate;
|
|
|
|
ofdma->of_dma_route_allocate = of_dma_route_allocate;
|
|
|
|
ofdma->dma_router = dma_router;
|
|
|
|
|
|
|
|
/* Now queue of_dma controller structure in list */
|
|
|
|
mutex_lock(&of_dma_lock);
|
|
|
|
list_add_tail(&ofdma->of_dma_controllers, &of_dma_list);
|
|
|
|
mutex_unlock(&of_dma_lock);
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(of_dma_router_register);
|
|
|
|
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
/**
|
2012-09-26 01:59:31 +07:00
|
|
|
* of_dma_match_channel - Check if a DMA specifier matches name
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
* @np: device node to look for DMA channels
|
2012-09-26 01:59:31 +07:00
|
|
|
* @name: channel name to be matched
|
|
|
|
* @index: index of DMA specifier in list of DMA specifiers
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
* @dma_spec: pointer to DMA specifier as found in the device tree
|
|
|
|
*
|
2012-09-26 01:59:31 +07:00
|
|
|
* Check if the DMA specifier pointed to by the index in a list of DMA
|
|
|
|
* specifiers, matches the name provided. Returns 0 if the name matches and
|
|
|
|
* a valid pointer to the DMA specifier is found. Otherwise returns -ENODEV.
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
*/
|
2013-02-24 22:36:09 +07:00
|
|
|
static int of_dma_match_channel(struct device_node *np, const char *name,
|
|
|
|
int index, struct of_phandle_args *dma_spec)
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
{
|
|
|
|
const char *s;
|
|
|
|
|
2012-09-26 01:59:31 +07:00
|
|
|
if (of_property_read_string_index(np, "dma-names", index, &s))
|
|
|
|
return -ENODEV;
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
2012-09-26 01:59:31 +07:00
|
|
|
if (strcmp(name, s))
|
|
|
|
return -ENODEV;
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
2012-09-26 01:59:31 +07:00
|
|
|
if (of_parse_phandle_with_args(np, "dmas", "#dma-cells", index,
|
|
|
|
dma_spec))
|
|
|
|
return -ENODEV;
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
2012-09-26 01:59:31 +07:00
|
|
|
return 0;
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* of_dma_request_slave_channel - Get the DMA slave channel
|
|
|
|
* @np: device node to get DMA request from
|
|
|
|
* @name: name of desired channel
|
|
|
|
*
|
dma: add channel request API that supports deferred probe
dma_request_slave_channel() simply returns NULL whenever DMA channel
lookup fails. Lookup could fail for two distinct reasons:
a) No DMA specification exists for the channel name.
This includes situations where no DMA specifications exist at all, or
other general lookup problems.
b) A DMA specification does exist, yet the driver for that channel is not
yet registered.
Case (b) should trigger deferred probe in client drivers. However, since
they have no way to differentiate the two situations, it cannot.
Implement new function dma_request_slave_channel_reason(), which performs
identically to dma_request_slave_channel(), except that it returns an
error-pointer rather than NULL, which allows callers to detect when
deferred probe should occur.
Eventually, all drivers should be converted to this new API, the old API
removed, and the new API renamed to the more desirable name. This patch
doesn't convert the existing API and all drivers in one go, since some
drivers call dma_request_slave_channel() then dma_request_channel() if
that fails. That would require either modifying dma_request_channel() in
the same way, or adding extra error-handling code to all affected
drivers, and there are close to 100 drivers using the other API, rather
than just the 15-20 or so that use dma_request_slave_channel(), which
might be tenable in a single patch.
acpi_dma_request_slave_chan_by_name() doesn't currently implement
deferred probe. It should, but this will be addressed later.
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2013-11-27 00:04:22 +07:00
|
|
|
* Returns pointer to appropriate DMA channel on success or an error pointer.
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
*/
|
|
|
|
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
|
2013-02-24 22:36:09 +07:00
|
|
|
const char *name)
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
{
|
|
|
|
struct of_phandle_args dma_spec;
|
|
|
|
struct of_dma *ofdma;
|
|
|
|
struct dma_chan *chan;
|
2016-05-11 20:15:11 +07:00
|
|
|
int count, i, start;
|
dma: add channel request API that supports deferred probe
dma_request_slave_channel() simply returns NULL whenever DMA channel
lookup fails. Lookup could fail for two distinct reasons:
a) No DMA specification exists for the channel name.
This includes situations where no DMA specifications exist at all, or
other general lookup problems.
b) A DMA specification does exist, yet the driver for that channel is not
yet registered.
Case (b) should trigger deferred probe in client drivers. However, since
they have no way to differentiate the two situations, it cannot.
Implement new function dma_request_slave_channel_reason(), which performs
identically to dma_request_slave_channel(), except that it returns an
error-pointer rather than NULL, which allows callers to detect when
deferred probe should occur.
Eventually, all drivers should be converted to this new API, the old API
removed, and the new API renamed to the more desirable name. This patch
doesn't convert the existing API and all drivers in one go, since some
drivers call dma_request_slave_channel() then dma_request_channel() if
that fails. That would require either modifying dma_request_channel() in
the same way, or adding extra error-handling code to all affected
drivers, and there are close to 100 drivers using the other API, rather
than just the 15-20 or so that use dma_request_slave_channel(), which
might be tenable in a single patch.
acpi_dma_request_slave_chan_by_name() doesn't currently implement
deferred probe. It should, but this will be addressed later.
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2013-11-27 00:04:22 +07:00
|
|
|
int ret_no_channel = -ENODEV;
|
2016-05-11 20:15:11 +07:00
|
|
|
static atomic_t last_index;
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
|
|
|
if (!np || !name) {
|
|
|
|
pr_err("%s: not enough information provided\n", __func__);
|
dma: add channel request API that supports deferred probe
dma_request_slave_channel() simply returns NULL whenever DMA channel
lookup fails. Lookup could fail for two distinct reasons:
a) No DMA specification exists for the channel name.
This includes situations where no DMA specifications exist at all, or
other general lookup problems.
b) A DMA specification does exist, yet the driver for that channel is not
yet registered.
Case (b) should trigger deferred probe in client drivers. However, since
they have no way to differentiate the two situations, it cannot.
Implement new function dma_request_slave_channel_reason(), which performs
identically to dma_request_slave_channel(), except that it returns an
error-pointer rather than NULL, which allows callers to detect when
deferred probe should occur.
Eventually, all drivers should be converted to this new API, the old API
removed, and the new API renamed to the more desirable name. This patch
doesn't convert the existing API and all drivers in one go, since some
drivers call dma_request_slave_channel() then dma_request_channel() if
that fails. That would require either modifying dma_request_channel() in
the same way, or adding extra error-handling code to all affected
drivers, and there are close to 100 drivers using the other API, rather
than just the 15-20 or so that use dma_request_slave_channel(), which
might be tenable in a single patch.
acpi_dma_request_slave_chan_by_name() doesn't currently implement
deferred probe. It should, but this will be addressed later.
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2013-11-27 00:04:22 +07:00
|
|
|
return ERR_PTR(-ENODEV);
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
}
|
|
|
|
|
2015-01-14 21:16:28 +07:00
|
|
|
/* Silently fail if there is not even the "dmas" property */
|
|
|
|
if (!of_find_property(np, "dmas", NULL))
|
|
|
|
return ERR_PTR(-ENODEV);
|
|
|
|
|
2012-09-26 01:59:31 +07:00
|
|
|
count = of_property_count_strings(np, "dma-names");
|
|
|
|
if (count < 0) {
|
2017-07-19 04:42:58 +07:00
|
|
|
pr_err("%s: dma-names property of node '%pOF' missing or empty\n",
|
|
|
|
__func__, np);
|
dma: add channel request API that supports deferred probe
dma_request_slave_channel() simply returns NULL whenever DMA channel
lookup fails. Lookup could fail for two distinct reasons:
a) No DMA specification exists for the channel name.
This includes situations where no DMA specifications exist at all, or
other general lookup problems.
b) A DMA specification does exist, yet the driver for that channel is not
yet registered.
Case (b) should trigger deferred probe in client drivers. However, since
they have no way to differentiate the two situations, it cannot.
Implement new function dma_request_slave_channel_reason(), which performs
identically to dma_request_slave_channel(), except that it returns an
error-pointer rather than NULL, which allows callers to detect when
deferred probe should occur.
Eventually, all drivers should be converted to this new API, the old API
removed, and the new API renamed to the more desirable name. This patch
doesn't convert the existing API and all drivers in one go, since some
drivers call dma_request_slave_channel() then dma_request_channel() if
that fails. That would require either modifying dma_request_channel() in
the same way, or adding extra error-handling code to all affected
drivers, and there are close to 100 drivers using the other API, rather
than just the 15-20 or so that use dma_request_slave_channel(), which
might be tenable in a single patch.
acpi_dma_request_slave_chan_by_name() doesn't currently implement
deferred probe. It should, but this will be addressed later.
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2013-11-27 00:04:22 +07:00
|
|
|
return ERR_PTR(-ENODEV);
|
2012-09-26 01:59:31 +07:00
|
|
|
}
|
|
|
|
|
2016-05-11 20:15:11 +07:00
|
|
|
/*
|
|
|
|
* approximate an average distribution across multiple
|
|
|
|
* entries with the same name
|
|
|
|
*/
|
|
|
|
start = atomic_inc_return(&last_index);
|
2012-09-26 01:59:31 +07:00
|
|
|
for (i = 0; i < count; i++) {
|
2016-05-11 20:15:11 +07:00
|
|
|
if (of_dma_match_channel(np, name,
|
|
|
|
(i + start) % count,
|
|
|
|
&dma_spec))
|
2012-09-26 01:59:31 +07:00
|
|
|
continue;
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
2013-04-19 16:42:14 +07:00
|
|
|
mutex_lock(&of_dma_lock);
|
|
|
|
ofdma = of_dma_find_controller(&dma_spec);
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
dma: add channel request API that supports deferred probe
dma_request_slave_channel() simply returns NULL whenever DMA channel
lookup fails. Lookup could fail for two distinct reasons:
a) No DMA specification exists for the channel name.
This includes situations where no DMA specifications exist at all, or
other general lookup problems.
b) A DMA specification does exist, yet the driver for that channel is not
yet registered.
Case (b) should trigger deferred probe in client drivers. However, since
they have no way to differentiate the two situations, it cannot.
Implement new function dma_request_slave_channel_reason(), which performs
identically to dma_request_slave_channel(), except that it returns an
error-pointer rather than NULL, which allows callers to detect when
deferred probe should occur.
Eventually, all drivers should be converted to this new API, the old API
removed, and the new API renamed to the more desirable name. This patch
doesn't convert the existing API and all drivers in one go, since some
drivers call dma_request_slave_channel() then dma_request_channel() if
that fails. That would require either modifying dma_request_channel() in
the same way, or adding extra error-handling code to all affected
drivers, and there are close to 100 drivers using the other API, rather
than just the 15-20 or so that use dma_request_slave_channel(), which
might be tenable in a single patch.
acpi_dma_request_slave_chan_by_name() doesn't currently implement
deferred probe. It should, but this will be addressed later.
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2013-11-27 00:04:22 +07:00
|
|
|
if (ofdma) {
|
2013-04-19 16:42:13 +07:00
|
|
|
chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
|
dma: add channel request API that supports deferred probe
dma_request_slave_channel() simply returns NULL whenever DMA channel
lookup fails. Lookup could fail for two distinct reasons:
a) No DMA specification exists for the channel name.
This includes situations where no DMA specifications exist at all, or
other general lookup problems.
b) A DMA specification does exist, yet the driver for that channel is not
yet registered.
Case (b) should trigger deferred probe in client drivers. However, since
they have no way to differentiate the two situations, it cannot.
Implement new function dma_request_slave_channel_reason(), which performs
identically to dma_request_slave_channel(), except that it returns an
error-pointer rather than NULL, which allows callers to detect when
deferred probe should occur.
Eventually, all drivers should be converted to this new API, the old API
removed, and the new API renamed to the more desirable name. This patch
doesn't convert the existing API and all drivers in one go, since some
drivers call dma_request_slave_channel() then dma_request_channel() if
that fails. That would require either modifying dma_request_channel() in
the same way, or adding extra error-handling code to all affected
drivers, and there are close to 100 drivers using the other API, rather
than just the 15-20 or so that use dma_request_slave_channel(), which
might be tenable in a single patch.
acpi_dma_request_slave_chan_by_name() doesn't currently implement
deferred probe. It should, but this will be addressed later.
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2013-11-27 00:04:22 +07:00
|
|
|
} else {
|
|
|
|
ret_no_channel = -EPROBE_DEFER;
|
2013-04-19 16:42:13 +07:00
|
|
|
chan = NULL;
|
dma: add channel request API that supports deferred probe
dma_request_slave_channel() simply returns NULL whenever DMA channel
lookup fails. Lookup could fail for two distinct reasons:
a) No DMA specification exists for the channel name.
This includes situations where no DMA specifications exist at all, or
other general lookup problems.
b) A DMA specification does exist, yet the driver for that channel is not
yet registered.
Case (b) should trigger deferred probe in client drivers. However, since
they have no way to differentiate the two situations, it cannot.
Implement new function dma_request_slave_channel_reason(), which performs
identically to dma_request_slave_channel(), except that it returns an
error-pointer rather than NULL, which allows callers to detect when
deferred probe should occur.
Eventually, all drivers should be converted to this new API, the old API
removed, and the new API renamed to the more desirable name. This patch
doesn't convert the existing API and all drivers in one go, since some
drivers call dma_request_slave_channel() then dma_request_channel() if
that fails. That would require either modifying dma_request_channel() in
the same way, or adding extra error-handling code to all affected
drivers, and there are close to 100 drivers using the other API, rather
than just the 15-20 or so that use dma_request_slave_channel(), which
might be tenable in a single patch.
acpi_dma_request_slave_chan_by_name() doesn't currently implement
deferred probe. It should, but this will be addressed later.
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2013-11-27 00:04:22 +07:00
|
|
|
}
|
2013-04-19 16:42:14 +07:00
|
|
|
|
|
|
|
mutex_unlock(&of_dma_lock);
|
2012-10-12 02:43:01 +07:00
|
|
|
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
of_node_put(dma_spec.np);
|
|
|
|
|
2012-09-26 01:59:31 +07:00
|
|
|
if (chan)
|
|
|
|
return chan;
|
|
|
|
}
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
dma: add channel request API that supports deferred probe
dma_request_slave_channel() simply returns NULL whenever DMA channel
lookup fails. Lookup could fail for two distinct reasons:
a) No DMA specification exists for the channel name.
This includes situations where no DMA specifications exist at all, or
other general lookup problems.
b) A DMA specification does exist, yet the driver for that channel is not
yet registered.
Case (b) should trigger deferred probe in client drivers. However, since
they have no way to differentiate the two situations, it cannot.
Implement new function dma_request_slave_channel_reason(), which performs
identically to dma_request_slave_channel(), except that it returns an
error-pointer rather than NULL, which allows callers to detect when
deferred probe should occur.
Eventually, all drivers should be converted to this new API, the old API
removed, and the new API renamed to the more desirable name. This patch
doesn't convert the existing API and all drivers in one go, since some
drivers call dma_request_slave_channel() then dma_request_channel() if
that fails. That would require either modifying dma_request_channel() in
the same way, or adding extra error-handling code to all affected
drivers, and there are close to 100 drivers using the other API, rather
than just the 15-20 or so that use dma_request_slave_channel(), which
might be tenable in a single patch.
acpi_dma_request_slave_chan_by_name() doesn't currently implement
deferred probe. It should, but this will be addressed later.
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2013-11-27 00:04:22 +07:00
|
|
|
return ERR_PTR(ret_no_channel);
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
}
|
2015-02-24 07:54:16 +07:00
|
|
|
EXPORT_SYMBOL_GPL(of_dma_request_slave_channel);
|
of: Add generic device tree DMA helpers
This is based upon the work by Benoit Cousson [1] and Nicolas Ferre [2]
to add some basic helpers to retrieve a DMA controller device_node and the
DMA request/channel information.
Aim of DMA helpers
- The purpose of device-tree is to describe the capabilites of the hardware.
Thinking about DMA controllers purely from the context of the hardware to
begin with, we can describe a device in terms of a DMA controller as
follows ...
1. Number of DMA controllers
2. Number of channels (maybe physical or logical)
3. Mapping of DMA requests signals to DMA controller
4. Number of DMA interrupts
5. Mapping of DMA interrupts to channels
- With the above in mind the aim of the DT DMA helper functions is to extract
the above information from the DT and provide to the appropriate driver.
However, due to the vast number of DMA controllers and not all are using a
common driver (such as DMA Engine) it has been seen that this is not a
trivial task. In previous discussions on this topic the following concerns
have been raised ...
1. How does the binding support devices with multiple DMA controllers?
2. How to support both legacy DMA controllers not using DMA Engine as
well as those that support DMA Engine.
3. When using with DMA Engine how do we support the various
implementations where the opaque filter function parameter differs
between implementations?
4. How do we handle DMA channels that are identified with a string
versus a integer?
- Hence the design of the DMA helpers has to accomodate the above or align on
an agreement what can be or should be supported.
Design of DMA helpers
1. Registering DMA controllers
In the case of DMA controllers that are using DMA Engine, requesting a
channel is performed by calling the following function.
struct dma_chan *dma_request_channel(dma_cap_mask_t mask,
dma_filter_fn filter_fn,
void *filter_param);
The mask variable is used to match a type of the device controller in a list
of controllers. The filter_fn and filter_param are used to identify the
required dma channel and return a handle to the dma channel of type dma_chan.
From the examples I have seen, the mask and filter_fn are constant
for a given DMA controller and therefore, we can specify these as controller
specific data when registering the DMA controller with the device-tree DMA
helpers.
The filter_param variable is of an unknown type and is typically specific
to the DMA engine implementation for a given DMA controller. To allow some
flexibility in the type and formating of this filter_param we employ an
xlate to translate the device-tree binding information into the appropriate
format. The xlate function used for a DMA controller can also be specified
when registering the DMA controller with the device-tree DMA helpers.
Based upon the above, a function for registering the DMA controller with the
DMA helpers now looks like the below. The data variable is used to pass a
pointer to DMA controller specific data used by the xlate function.
int of_dma_controller_register(struct device_node *np,
struct dma_chan *(*of_dma_xlate)
(struct of_phandle_args *, struct of_dma *),
void *data)
For example, in the case where DMA engine is used, we define the following
structure (that stores the DMA engine capability mask and filter function)
and pass this to the data variable in the above function.
struct of_dma_filter_info {
dma_cap_mask_t dma_cap;
dma_filter_fn filter_fn;
};
2. Representing and requesting channel information
Please see the dma binding documentation included in this patch for a
description of how DMA controllers and client information should be
represented with device-tree. For more information on how this binding
came about please see [3]. In addition to this, feedback received from
the Linux kernel summit showed a consensus (among those who attended) to
use a name to identify DMA client information [4].
A DMA channel can be requested by calling the following function, where name
is a required parameter used for identifying a DMA channel. This function
has been designed to return a structure of type dma_chan to work with the
DMA engine driver. Note that if DMA engine is used then drivers should be
using the DMA engine API dma_request_slave_channel() (implemented in part 2
of this series, "dmaengine: add helper function to request a slave DMA
channel") which will in turn call the below function if device-tree is
present. The aim being to have a common DMA engine interface regardless of
whether device tree is being used.
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
char *name)
3. Supporting legacy devices not using DMA Engine
These devices present a problem, as there may not be a uniform way to easily
support them with regard to device tree. Ideally, these should be migrated
to DMA engine. However, if this is not possible, then they should still be
able to use this binding, the only constaint imposed by this implementation
is that when requesting a DMA channel via of_dma_request_slave_channel(), it
will return a type of dma_chan.
This implementation has been tested on OMAP4430 using the kernel v3.6-rc5. I
have validated that MMC is working on the PANDA board with this implementation.
My development branch for testing on OMAP can be found here [5].
v6: - minor corrections in DMA binding documentation
v5: - minor update to binding documentation
- added loop to exhaustively search for a slave channel in the case where
there could be alternative channels available
v4: - revert the removal of xlate function from v3
- update the proposed binding format and APIs based upon discussions [3]
v3: - avoid passing an xlate function and instead pass DMA engine parameters
- define number of dma channels and requests in dma-controller node
v2: - remove of_dma_to_resource API
- make property #dma-cells required (no fallback anymore)
- another check in of_dma_xlate_onenumbercell() function
[1] http://article.gmane.org/gmane.linux.drivers.devicetree/12022
[2] http://article.gmane.org/gmane.linux.ports.arm.omap/73622
[3] http://marc.info/?l=linux-omap&m=133582085008539&w=2
[4] http://pad.linaro.org/arm-mini-summit-2012
[5] https://github.com/jonhunter/linux/tree/dev-dt-dma
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <djbw@fb.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Reviewed-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
2012-09-15 05:41:56 +07:00
|
|
|
|
|
|
|
/**
|
|
|
|
* of_dma_simple_xlate - Simple DMA engine translation function
|
|
|
|
* @dma_spec: pointer to DMA specifier as found in the device tree
|
|
|
|
* @of_dma: pointer to DMA controller data
|
|
|
|
*
|
|
|
|
* A simple translation function for devices that use a 32-bit value for the
|
|
|
|
* filter_param when calling the DMA engine dma_request_channel() function.
|
|
|
|
* Note that this translation function requires that #dma-cells is equal to 1
|
|
|
|
* and the argument of the dma specifier is the 32-bit filter_param. Returns
|
|
|
|
* pointer to appropriate dma channel on success or NULL on error.
|
|
|
|
*/
|
|
|
|
struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
|
|
|
|
struct of_dma *ofdma)
|
|
|
|
{
|
|
|
|
int count = dma_spec->args_count;
|
|
|
|
struct of_dma_filter_info *info = ofdma->of_dma_data;
|
|
|
|
|
|
|
|
if (!info || !info->filter_fn)
|
|
|
|
return NULL;
|
|
|
|
|
|
|
|
if (count != 1)
|
|
|
|
return NULL;
|
|
|
|
|
|
|
|
return dma_request_channel(info->dma_cap, info->filter_fn,
|
|
|
|
&dma_spec->args[0]);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
|
2014-06-25 17:52:59 +07:00
|
|
|
|
|
|
|
/**
|
|
|
|
* of_dma_xlate_by_chan_id - Translate dt property to DMA channel by channel id
|
|
|
|
* @dma_spec: pointer to DMA specifier as found in the device tree
|
|
|
|
* @of_dma: pointer to DMA controller data
|
|
|
|
*
|
|
|
|
* This function can be used as the of xlate callback for DMA driver which wants
|
|
|
|
* to match the channel based on the channel id. When using this xlate function
|
|
|
|
* the #dma-cells propety of the DMA controller dt node needs to be set to 1.
|
|
|
|
* The data parameter of of_dma_controller_register must be a pointer to the
|
|
|
|
* dma_device struct the function should match upon.
|
|
|
|
*
|
|
|
|
* Returns pointer to appropriate dma channel on success or NULL on error.
|
|
|
|
*/
|
|
|
|
struct dma_chan *of_dma_xlate_by_chan_id(struct of_phandle_args *dma_spec,
|
|
|
|
struct of_dma *ofdma)
|
|
|
|
{
|
|
|
|
struct dma_device *dev = ofdma->of_dma_data;
|
|
|
|
struct dma_chan *chan, *candidate = NULL;
|
|
|
|
|
|
|
|
if (!dev || dma_spec->args_count != 1)
|
|
|
|
return NULL;
|
|
|
|
|
|
|
|
list_for_each_entry(chan, &dev->channels, device_node)
|
|
|
|
if (chan->chan_id == dma_spec->args[0]) {
|
|
|
|
candidate = chan;
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (!candidate)
|
|
|
|
return NULL;
|
|
|
|
|
|
|
|
return dma_get_slave_channel(candidate);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(of_dma_xlate_by_chan_id);
|