[PATCH v2] pinctrl: indicate GPIO direction on single GPIO request

[Linus Walleij]

From: Linus Walleij <linus.walleij@xxxxxxxxxx>

When requesting a single GPIO pin to be muxed in, some controllers
will need to poke a different value into the control register
depending on whether the pin will be used for GPIO output or GPIO
input. So pass this info along for the gpio_request_enable()
function, we assume this is not needed for the gpio_free_disable()
function for the time being.

ChangeLog V1->V2:
- This also amends the documentation to make it clear the this
  function and associated machinery is *ONLY* intended as a backend
  to gpiolib machinery, not for everyone and his dog to start playing
  around with pins.

Suggested-by: Thomas Abraham <thomas.abraham@xxxxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
 Documentation/pinctrl.txt      |   30 +++++++++++++++++++++---------
 drivers/pinctrl/pinmux.c       |   26 +++++++++++++++++++++-----
 include/linux/pinctrl/pinmux.h |   14 ++++++++++----
 3 files changed, 52 insertions(+), 18 deletions(-)

diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt
index 214b961..226f252 100644
--- a/Documentation/pinctrl.txt
+++ b/Documentation/pinctrl.txt
@@ -645,6 +645,15 @@ All the above functions are mandatory to implement for a pinmux driver.
 Pinmux interaction with the GPIO subsystem
 ==========================================
 
+The public pinmux API contains two functions named pinmux_request_gpio()
+and pinmux_free_gpio(). These two functions shall *ONLY* be called from
+gpiolib-based drivers as part of their gpio_request() and
+gpio_direction_[input|output() semantics.
+
+NOTE that platforms and individual driver shall *NOT* request GPIO pins to be
+muxed in. Instead, implement a proper gpiolib driver hand have that driver
+request proper muxing for its pins.
+
 The function list could become long, especially if you can convert every
 individual pin into a GPIO pin independent of any other pins, and then try
 the approach to define every pin as a function.
@@ -652,19 +661,22 @@ the approach to define every pin as a function.
 In this case, the function array would become 64 entries for each GPIO
 setting and then the device functions.
 
-For this reason there is an additional function a pinmux driver can implement
-to enable only GPIO on an individual pin: .gpio_request_enable(). The same
-.free() function as for other functions is assumed to be usable also for
-GPIO pins.
+For this reason there are two functions a pinmux driver can implement
+to enable only GPIO on an individual pin: .gpio_request_enable() and
+.gpio_disable_free().
 
 This function will pass in the affected GPIO range identified by the pin
 controller core, so you know which GPIO pins are being affected by the request
-operation.
+operation. The gpio_request_enable() call will also indicate if the pin shall
+be multiplexed for input or output as some pin controllers have different
+multiplexing settings for these two cases.
 
-Alternatively it is fully allowed to use named functions for each GPIO
-pin, the pinmux_request_gpio() will attempt to obtain the function "gpioN"
-where "N" is the global GPIO pin number if no special GPIO-handler is
-registered.
+Alternatively to using these special functions, it is fully allowed to use
+named functions for each GPIO pin, the pinmux_request_gpio() will attempt to
+obtain the function "gpioN" where "N" is the global GPIO pin number if no
+special GPIO-handler is registered.
+
+The public functions to enable a certain GPIO pin
 
 
 Pinmux board/machine configuration
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index d27b77d..9c46e5e 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -100,10 +100,13 @@ struct pinmux_hog {
  *	means that you want to mux in the pin for use as GPIO number NN
  * @gpio_range: the range matching the GPIO pin if this is a request for a
  *	single GPIO pin
+ * @gpio_direction: if the pin is muxed for GPIO, this provides the direction
+ *	of the GPIO @true means output, @false means input
  */
 static int pin_request(struct pinctrl_dev *pctldev,
 		       int pin, const char *function,
-		       struct pinctrl_gpio_range *gpio_range)
+		       struct pinctrl_gpio_range *gpio_range,
+		       bool gpio_direction)
 {
 	struct pin_desc *desc;
 	const struct pinmux_ops *ops = pctldev->desc->pmxops;
@@ -148,7 +151,8 @@ static int pin_request(struct pinctrl_dev *pctldev,
 	 */
 	if (gpio_range && ops->gpio_request_enable)
 		/* This requests and enables a single GPIO pin */
-		status = ops->gpio_request_enable(pctldev, gpio_range, pin);
+	  status = ops->gpio_request_enable(pctldev, gpio_range, pin,
+					    gpio_direction);
 	else if (ops->request)
 		status = ops->request(pctldev, pin);
 	else
@@ -218,8 +222,15 @@ static const char *pin_free(struct pinctrl_dev *pctldev, int pin,
 /**
  * pinmux_request_gpio() - request a single pin to be muxed in as GPIO
  * @gpio: the GPIO pin number from the GPIO subsystem number space
+ * @direction: the direction of the GPIO, @true means output, @false
+ *	means input
+ *
+ * This function should *ONLY* be used from gpiolib-based GPIO drivers,
+ * as part of their gpio_request() and gpio_direction_[input|output()
+ * semantics, platforms and individual driver shall *NOT* request GPIO pins to
+ * be muxed in.
  */
-int pinmux_request_gpio(unsigned gpio)
+int pinmux_request_gpio(unsigned gpio, bool direction)
 {
 	char gpiostr[16];
 	const char *function;
@@ -242,7 +253,7 @@ int pinmux_request_gpio(unsigned gpio)
 	if (!function)
 		return -EINVAL;
 
-	ret = pin_request(pctldev, pin, function, range);
+	ret = pin_request(pctldev, pin, function, range, direction);
 	if (ret < 0)
 		kfree(function);
 
@@ -253,6 +264,11 @@ EXPORT_SYMBOL_GPL(pinmux_request_gpio);
 /**
  * pinmux_free_gpio() - free a single pin, currently used as GPIO
  * @gpio: the GPIO pin number from the GPIO subsystem number space
+ *
+ * This function should *ONLY* be used from gpiolib-based GPIO drivers,
+ * as part of their gpio_request() and gpio_direction_[input|output()
+ * semantics, platforms and individual driver shall *NOT* request GPIO pins to
+ * be muxed in.
  */
 void pinmux_free_gpio(unsigned gpio)
 {
@@ -360,7 +376,7 @@ static int acquire_pins(struct pinctrl_dev *pctldev,
 
 	/* Try to allocate all pins in this group, one by one */
 	for (i = 0; i < num_pins; i++) {
-		ret = pin_request(pctldev, pins[i], func, NULL);
+	  ret = pin_request(pctldev, pins[i], func, NULL, false);
 		if (ret) {
 			dev_err(&pctldev->dev,
 				"could not get pin %d for function %s "
diff --git a/include/linux/pinctrl/pinmux.h b/include/linux/pinctrl/pinmux.h
index bb7a979..7d3841f 100644
--- a/include/linux/pinctrl/pinmux.h
+++ b/include/linux/pinctrl/pinmux.h
@@ -54,7 +54,12 @@ struct pinctrl_dev;
  *	Implement this only if you can mux every pin individually as GPIO. The
  *	affected GPIO range is passed along with an offset(pin number) into that
  *	specific GPIO range - function selectors and pin groups are orthogonal
- *	to this, the core will however make sure the pins do not collide
+ *	to this, the core will however make sure the pins do not collide. Since
+ *	controllers may be needing different configurations depending on
+ *	whether the GPIO is configured as input or output, a direction
+ *	indicator is passed along
+ * @gpio_disable_free: free up GPIO muxing on a certain pin, the reverse of
+ *	@gpio_request_enable
  */
 struct pinmux_ops {
 	int (*request) (struct pinctrl_dev *pctldev, unsigned offset);
@@ -72,14 +77,15 @@ struct pinmux_ops {
 			 unsigned group_selector);
 	int (*gpio_request_enable) (struct pinctrl_dev *pctldev,
 				    struct pinctrl_gpio_range *range,
-				    unsigned offset);
+				    unsigned offset,
+				    bool direction);
 	void (*gpio_disable_free) (struct pinctrl_dev *pctldev,
 				   struct pinctrl_gpio_range *range,
 				   unsigned offset);
 };
 
 /* External interface to pinmux */
-extern int pinmux_request_gpio(unsigned gpio);
+extern int pinmux_request_gpio(unsigned gpio, bool direction);
 extern void pinmux_free_gpio(unsigned gpio);
 extern struct pinmux * __must_check pinmux_get(struct device *dev, const char *name);
 extern void pinmux_put(struct pinmux *pmx);
@@ -88,7 +94,7 @@ extern void pinmux_disable(struct pinmux *pmx);
 
 #else /* !CONFIG_PINMUX */
 
-static inline int pinmux_request_gpio(unsigned gpio)
+static inline int pinmux_request_gpio(unsigned gpio, bool direction)
 {
 	return 0;
 }
-- 
1.7.3.2

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