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mfd: Add refcounting support to mfd_cells

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This provides convenience functions for sharing of cells across
multiple mfd clients.  Mfd drivers can provide enable/disable hooks
to actually tweak the hardware, and clients can call
mfd_shared_cell_{en,dis}able without having to worry about whether
or not another client happens to have enabled or disabled the
cell/hardware.

Note that this is purely optional; drivers can continue to use
the mfd_cell's enable/disable hooks for their own purposes, if
desired.

Signed-off-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
This commit is contained in:
Andres Salomon 2011-02-17 19:07:34 -08:00 committed by Samuel Ortiz
parent dcb50e83bb
commit 1e29af62f2
2 changed files with 73 additions and 5 deletions
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64
drivers/mfd/mfd-core.c
View File

@ -18,6 +18,43 @@
#include <linux/pm_runtime.h>
#include <linux/slab.h>
int mfd_shared_cell_enable(struct platform_device *pdev)
{
const struct mfd_cell *cell = mfd_get_cell(pdev);
int err = 0;
/* only call enable hook if the cell wasn't previously enabled */
if (atomic_inc_return(cell->usage_count) == 1)
err = cell->enable(pdev);
/* if the enable hook failed, decrement counter to allow retries */
if (err)
atomic_dec(cell->usage_count);
return err;
}
EXPORT_SYMBOL(mfd_shared_cell_enable);
int mfd_shared_cell_disable(struct platform_device *pdev)
{
const struct mfd_cell *cell = mfd_get_cell(pdev);
int err = 0;
/* only disable if no other clients are using it */
if (atomic_dec_return(cell->usage_count) == 0)
err = cell->disable(pdev);
/* if the disable hook failed, increment to allow retries */
if (err)
atomic_inc(cell->usage_count);
/* sanity check; did someone call disable too many times? */
WARN_ON(atomic_read(cell->usage_count) < 0);
return err;
}
EXPORT_SYMBOL(mfd_shared_cell_disable);
static int mfd_add_device(struct device *parent, int id,
const struct mfd_cell *cell,
struct resource *mem_base,
@ -96,14 +133,22 @@ static int mfd_add_device(struct device *parent, int id,
}
int mfd_add_devices(struct device *parent, int id,
const struct mfd_cell *cells, int n_devs,
struct mfd_cell *cells, int n_devs,
struct resource *mem_base,
int irq_base)
{
int i;
int ret = 0;
atomic_t *cnts;
/* initialize reference counting for all cells */
cnts = kcalloc(sizeof(*cnts), n_devs, GFP_KERNEL);
if (!cnts)
return -ENOMEM;
for (i = 0; i < n_devs; i++) {
atomic_set(&cnts[i], 0);
cells[i].usage_count = &cnts[i];
ret = mfd_add_device(parent, id, cells + i, mem_base, irq_base);
if (ret)
break;
@ -116,15 +161,26 @@ int mfd_add_devices(struct device *parent, int id,
}
EXPORT_SYMBOL(mfd_add_devices);
static int mfd_remove_devices_fn(struct device *dev, void *unused)
static int mfd_remove_devices_fn(struct device *dev, void *c)
{
platform_device_unregister(to_platform_device(dev));
struct platform_device *pdev = to_platform_device(dev);
const struct mfd_cell *cell = mfd_get_cell(pdev);
atomic_t **usage_count = c;
/* find the base address of usage_count pointers (for freeing) */
if (!*usage_count || (cell->usage_count < *usage_count))
*usage_count = cell->usage_count;
platform_device_unregister(pdev);
return 0;
}
void mfd_remove_devices(struct device *parent)
{
device_for_each_child(parent, NULL, mfd_remove_devices_fn);
atomic_t *cnts = NULL;
device_for_each_child(parent, &cnts, mfd_remove_devices_fn);
kfree(cnts);
}
EXPORT_SYMBOL(mfd_remove_devices);

14
include/linux/mfd/core.h
View File

@ -25,8 +25,11 @@ struct mfd_cell {
const char *name;
int id;
/* refcounting for multiple drivers to use a single cell */
atomic_t *usage_count;
int (*enable)(struct platform_device *dev);
int (*disable)(struct platform_device *dev);
int (*suspend)(struct platform_device *dev);
int (*resume)(struct platform_device *dev);
@ -50,6 +53,15 @@ struct mfd_cell {
bool pm_runtime_no_callbacks;
};
/*
* Convenience functions for clients using shared cells. Refcounting
* happens automatically, with the cell's enable/disable callbacks
* being called only when a device is first being enabled or no other
* clients are making use of it.
*/
extern int mfd_shared_cell_enable(struct platform_device *pdev);
extern int mfd_shared_cell_disable(struct platform_device *pdev);
/*
* Given a platform device that's been created by mfd_add_devices(), fetch
* the mfd_cell that created it.
@ -69,7 +81,7 @@ static inline void *mfd_get_data(struct platform_device *pdev)
}
extern int mfd_add_devices(struct device *parent, int id,
const struct mfd_cell *cells, int n_devs,
struct mfd_cell *cells, int n_devs,
struct resource *mem_base,
int irq_base);