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2243a87d90
What the patch does: 1. Call pinmux_disable_setting ahead of pinmux_enable_setting each time pinctrl_select_state is called 2. Remove the HW disable operation in pinmux_disable_setting function. 3. Remove the disable ops in struct pinmux_ops 4. Remove all the disable ops users in current code base. Notes: 1. Great thanks for the suggestion from Linus, Tony Lindgren and Stephen Warren and Everyone that shared comments on this patch. 2. The patch also includes comment fixes from Stephen Warren. The reason why we do this: 1. To avoid duplicated calling of the enable_setting operation without disabling operation inbetween which will let the pin descriptor desc->mux_usecount increase monotonously. 2. The HW pin disable operation is not useful for any of the existing platforms. And this can be used to avoid the HW glitch after using the item #1 modification. In the following case, the issue can be reproduced: 1. There is a driver that need to switch pin state dynamically, e.g. between "sleep" and "default" state 2. The pin setting configuration in a DTS node may be like this: component a { pinctrl-names = "default", "sleep"; pinctrl-0 = <&a_grp_setting &c_grp_setting>; pinctrl-1 = <&b_grp_setting &c_grp_setting>; } The "c_grp_setting" config node is totally identical, maybe like following one: c_grp_setting: c_grp_setting { pinctrl-single,pins = <GPIO48 AF6>; } 3. When switching the pin state in the following official pinctrl sequence: pin = pinctrl_get(); state = pinctrl_lookup_state(wanted_state); pinctrl_select_state(state); pinctrl_put(); Test Result: 1. The switch is completed as expected, that is: the device's pin configuration is changed according to the description in the "wanted_state" group setting 2. The "desc->mux_usecount" of the corresponding pins in "c_group" is increased without being decreased, because the "desc" is for each physical pin while the setting is for each setting node in the DTS. Thus, if the "c_grp_setting" in pinctrl-0 is not disabled ahead of enabling "c_grp_setting" in pinctrl-1, the desc->mux_usecount will keep increasing without any chance to be decreased. According to the comments in the original code, only the setting, in old state but not in new state, will be "disabled" (calling pinmux_disable_setting), which is correct logic but not intact. We still need consider case that the setting is in both old state and new state. We can do this in the following two ways: 1. Avoid to "enable"(calling pinmux_enable_setting) the "same pin setting" repeatedly 2. "Disable"(calling pinmux_disable_setting) the "same pin setting", actually two setting instances, ahead of enabling them. Analysis: 1. The solution #2 is better because it can avoid too much iteration. 2. If we disable all of the settings in the old state and one of the setting(s) exist in the new state, the pins mux function change may happen when some SoC vendors defined the "pinctrl-single,function-off" in their DTS file. old_setting => disabled_setting => new_setting. 3. In the pinmux framework, when a pin state is switched, the setting in the old state should be marked as "disabled". Conclusion: 1. To Remove the HW disabling operation to above the glitch mentioned above. 2. Handle the issue mentioned above by disabling all of the settings in old state and then enable the all of the settings in new state. Signed-off-by: Fan Wu <fwu@marvell.com> Acked-by: Stephen Warren <swarren@nvidia.com> Acked-by: Patrice Chotard <patrice.chotard@st.com> Acked-by: Heiko Stuebner <heiko@sntech.de> Acked-by: Maxime Coquelin <maxime.coquelin@st.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
88 lines
3.7 KiB
C
88 lines
3.7 KiB
C
/*
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* Interface the pinmux subsystem
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*
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* Copyright (C) 2011 ST-Ericsson SA
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* Written on behalf of Linaro for ST-Ericsson
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* Based on bits of regulator core, gpio core and clk core
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*
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* Author: Linus Walleij <linus.walleij@linaro.org>
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*
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* License terms: GNU General Public License (GPL) version 2
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*/
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#ifndef __LINUX_PINCTRL_PINMUX_H
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#define __LINUX_PINCTRL_PINMUX_H
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#include <linux/list.h>
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#include <linux/seq_file.h>
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#include <linux/pinctrl/pinctrl.h>
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#ifdef CONFIG_PINMUX
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struct pinctrl_dev;
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/**
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* struct pinmux_ops - pinmux operations, to be implemented by pin controller
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* drivers that support pinmuxing
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* @request: called by the core to see if a certain pin can be made
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* available for muxing. This is called by the core to acquire the pins
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* before selecting any actual mux setting across a function. The driver
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* is allowed to answer "no" by returning a negative error code
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* @free: the reverse function of the request() callback, frees a pin after
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* being requested
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* @get_functions_count: returns number of selectable named functions available
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* in this pinmux driver
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* @get_function_name: return the function name of the muxing selector,
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* called by the core to figure out which mux setting it shall map a
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* certain device to
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* @get_function_groups: return an array of groups names (in turn
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* referencing pins) connected to a certain function selector. The group
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* name can be used with the generic @pinctrl_ops to retrieve the
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* actual pins affected. The applicable groups will be returned in
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* @groups and the number of groups in @num_groups
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* @enable: enable a certain muxing function with a certain pin group. The
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* driver does not need to figure out whether enabling this function
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* conflicts some other use of the pins in that group, such collisions
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* are handled by the pinmux subsystem. The @func_selector selects a
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* certain function whereas @group_selector selects a certain set of pins
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* to be used. On simple controllers the latter argument may be ignored
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* @disable: disable a certain muxing selector with a certain pin group
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* @gpio_request_enable: requests and enables GPIO on a certain pin.
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* Implement this only if you can mux every pin individually as GPIO. The
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* affected GPIO range is passed along with an offset(pin number) into that
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* specific GPIO range - function selectors and pin groups are orthogonal
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* to this, the core will however make sure the pins do not collide.
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* @gpio_disable_free: free up GPIO muxing on a certain pin, the reverse of
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* @gpio_request_enable
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* @gpio_set_direction: Since controllers may need different configurations
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* depending on whether the GPIO is configured as input or output,
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* a direction selector function may be implemented as a backing
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* to the GPIO controllers that need pin muxing.
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*/
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struct pinmux_ops {
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int (*request) (struct pinctrl_dev *pctldev, unsigned offset);
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int (*free) (struct pinctrl_dev *pctldev, unsigned offset);
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int (*get_functions_count) (struct pinctrl_dev *pctldev);
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const char *(*get_function_name) (struct pinctrl_dev *pctldev,
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unsigned selector);
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int (*get_function_groups) (struct pinctrl_dev *pctldev,
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unsigned selector,
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const char * const **groups,
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unsigned * const num_groups);
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int (*enable) (struct pinctrl_dev *pctldev, unsigned func_selector,
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unsigned group_selector);
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int (*gpio_request_enable) (struct pinctrl_dev *pctldev,
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struct pinctrl_gpio_range *range,
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unsigned offset);
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void (*gpio_disable_free) (struct pinctrl_dev *pctldev,
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struct pinctrl_gpio_range *range,
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unsigned offset);
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int (*gpio_set_direction) (struct pinctrl_dev *pctldev,
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struct pinctrl_gpio_range *range,
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unsigned offset,
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bool input);
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};
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#endif /* CONFIG_PINMUX */
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#endif /* __LINUX_PINCTRL_PINMUX_H */
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