gpio: gpiolib: Generalise state persistence beyond sleep

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>

4 files changed, 13 insertions, 3 deletions

diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 7447d85dbe2f..540b2c142493 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -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 */
diff --git a/include/linux/gpio/machine.h b/include/linux/gpio/machine.h
index 846be7c69a52..b2f2dc638463 100644
--- a/include/linux/gpio/machine.h
+++ b/include/linux/gpio/machine.h
@@ -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),
 };
 
 /**
diff --git a/include/linux/of_gpio.h b/include/linux/of_gpio.h
index 1fe205582111..18a7f03e1182 100644
--- a/include/linux/of_gpio.h
+++ b/include/linux/of_gpio.h
@@ -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
diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h
index ec6dadcc1fde..6c0680641108 100644
--- a/include/linux/pinctrl/pinconf-generic.h
+++ b/include/linux/pinctrl/pinconf-generic.h
@@ -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,
 };