pinctrl: GPIO direction support for muxing

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 create pinmux counterparts to gpio_direction_[input|output]
in the pinctrl framework.

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.
ChangeLog v2->v3:
- Don't pass an argument to the common request function, instead
  provide pinmux_* counterparts to the gpio_direction_[input|output]
  calls, simpler and anyone can understand it.
ChangeLog v3->v4:
- Fix numerous spelling mistakes and dangling text in documentation.
  Add Ack and Rewewed-by.

Cc: Igor Grinberg <grinberg@compulab.co.il>
Acked-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Thomas Abraham <thomas.abraham@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 61 insertions, 0 deletions

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 92aa13ee2208..f3e4f031fe1c 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -214,6 +214,10 @@ 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
+ *
+ * This function should *ONLY* be used from gpiolib-based GPIO drivers,
+ * as part of their gpio_request() semantics, platforms and individual drivers
+ * shall *NOT* request GPIO pins to be muxed in.
  */
 int pinmux_request_gpio(unsigned gpio)
 {
@@ -249,6 +253,10 @@ 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_free() semantics, platforms and individual drivers
+ * shall *NOT* request GPIO pins to be muxed out.
  */
 void pinmux_free_gpio(unsigned gpio)
 {
@@ -270,6 +278,59 @@ void pinmux_free_gpio(unsigned gpio)
 }
 EXPORT_SYMBOL_GPL(pinmux_free_gpio);
 
+static int pinmux_gpio_direction(unsigned gpio, bool input)
+{
+        struct pinctrl_dev *pctldev;
+        struct pinctrl_gpio_range *range;
+        const struct pinmux_ops *ops;
+        int ret;
+        int pin;
+
+        ret = pinctrl_get_device_gpio_range(gpio, &pctldev, &range);
+        if (ret)
+                return ret;
+
+        ops = pctldev->desc->pmxops;
+
+        /* Convert to the pin controllers number space */
+        pin = gpio - range->base + range->pin_base;
+
+        if (ops->gpio_set_direction)
+                ret = ops->gpio_set_direction(pctldev, range, pin, input);
+        else
+                ret = 0;
+
+        return ret;
+}
+
+/**
+ * pinmux_gpio_direction_input() - request a GPIO pin to go into input mode
+ * @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_direction_input() semantics, platforms and individual
+ * drivers shall *NOT* touch pinmux GPIO calls.
+ */
+int pinmux_gpio_direction_input(unsigned gpio)
+{
+        return pinmux_gpio_direction(gpio, true);
+}
+EXPORT_SYMBOL_GPL(pinmux_gpio_direction_input);
+
+/**
+ * pinmux_gpio_direction_output() - request a GPIO pin to go into output mode
+ * @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_direction_output() semantics, platforms and individual
+ * drivers shall *NOT* touch pinmux GPIO calls.
+ */
+int pinmux_gpio_direction_output(unsigned gpio)
+{
+        return pinmux_gpio_direction(gpio, false);
+}
+EXPORT_SYMBOL_GPL(pinmux_gpio_direction_output);
+
 /**
  * pinmux_register_mappings() - register a set of pinmux mappings
  * @maps: the pinmux mappings table to register