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gpio: gpiolib: Generalise state persistence beyond sleep

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General support for state persistence is added to gpiolib with the
introduction of a new pinconf parameter to propagate the request to
hardware. The existing persistence support for sleep is adapted to
include hardware support if the GPIO driver provides it. Persistence
continues to be enabled by default; in-kernel consumers can opt out, but
userspace (currently) does not have a choice.

The *_SLEEP_MAY_LOSE_VALUE and *_SLEEP_MAINTAIN_VALUE symbols are
renamed, dropping the SLEEP prefix to reflect that the concept is no
longer sleep-specific.  I feel that renaming to just *_MAY_LOSE_VALUE
could initially be misinterpreted, so I've further changed the symbols
to *_TRANSITORY and *_PERSISTENT to address this.

The sysfs interface is modified only to keep consistency with the
chardev interface in enforcing persistence for userspace exports.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Andrew Jeffery 2017-11-30 14:25:24 +10:30 • committed by Linus Walleij
parent e2843cb6cd
commit e10f72bf4b
9 changed files with 87 additions and 18 deletions
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8
include/linux/gpio/consumer.h
View file

@ -139,6 +139,7 @@ void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
int *value_array);
int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce);
int gpiod_set_transitory(struct gpio_desc *desc, bool transitory);
int gpiod_is_active_low(const struct gpio_desc *desc);
int gpiod_cansleep(const struct gpio_desc *desc);
@ -431,6 +432,13 @@ static inline int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
return -ENOSYS;
}
static inline int gpiod_set_transitory(struct gpio_desc *desc, bool transitory)
{
/* GPIO can never have been requested */
WARN_ON(1);
return -ENOSYS;
}
static inline int gpiod_is_active_low(const struct gpio_desc *desc)
{
/* GPIO can never have been requested */

4
include/linux/gpio/machine.h
View file

@ -10,8 +10,8 @@ enum gpio_lookup_flags {
GPIO_ACTIVE_LOW = (1 << 0),
GPIO_OPEN_DRAIN = (1 << 1),
GPIO_OPEN_SOURCE = (1 << 2),
GPIO_SLEEP_MAINTAIN_VALUE = (0 << 3),
GPIO_SLEEP_MAY_LOSE_VALUE = (1 << 3),
GPIO_PERSISTENT = (0 << 3),
GPIO_TRANSITORY = (1 << 3),
};
/**

2
include/linux/of_gpio.h
View file

@ -31,7 +31,7 @@ enum of_gpio_flags {
OF_GPIO_ACTIVE_LOW = 0x1,
OF_GPIO_SINGLE_ENDED = 0x2,
OF_GPIO_OPEN_DRAIN = 0x4,
OF_GPIO_SLEEP_MAY_LOSE_VALUE = 0x8,
OF_GPIO_TRANSITORY = 0x8,
};
#ifdef CONFIG_OF_GPIO

2
include/linux/pinctrl/pinconf-generic.h
View file

@ -94,6 +94,7 @@
* or latch delay (on outputs) this parameter (in a custom format)
* specifies the clock skew or latch delay. It typically controls how
* many double inverters are put in front of the line.
* @PIN_CONFIG_PERSIST_STATE: retain pin state across sleep or controller reset
* @PIN_CONFIG_END: this is the last enumerator for pin configurations, if
* you need to pass in custom configurations to the pin controller, use
* PIN_CONFIG_END+1 as the base offset.
@ -122,6 +123,7 @@ enum pin_config_param {
PIN_CONFIG_SLEEP_HARDWARE_STATE,
PIN_CONFIG_SLEW_RATE,
PIN_CONFIG_SKEW_DELAY,
PIN_CONFIG_PERSIST_STATE,
PIN_CONFIG_END = 0x7F,
PIN_CONFIG_MAX = 0xFF,
};