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>
diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt
index 43ba411..3846264 100644
--- a/Documentation/pinctrl.txt
+++ b/Documentation/pinctrl.txt
@@ -645,6 +645,17 @@
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_free() semantics. Likewise the pinmux_gpio_direction_[input|output]
+shall only be called from within respective gpio_direction_[input|output]
+gpiolib implementation.
+
+NOTE that platforms and individual drivers shall *NOT* request GPIO pins to be
+muxed in. Instead, implement a proper gpiolib driver and 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 +663,24 @@
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.
-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.
+If your driver needs to have an indication from the framework of whether the
+GPIO pin shall be used for input or output you can implement the
+.gpio_set_direction() function. As described this shall be called from the
+gpiolib driver and the affected GPIO range, pin offset and desired direction
+will be passed along to this function.
+
+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.
Pinmux board/machine configuration
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 92aa13e..f3e4f03 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -214,6 +214,10 @@
/**
* 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 @@
/**
* 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 @@
}
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
diff --git a/include/linux/pinctrl/pinmux.h b/include/linux/pinctrl/pinmux.h
index bb7a979..937b3e2 100644
--- a/include/linux/pinctrl/pinmux.h
+++ b/include/linux/pinctrl/pinmux.h
@@ -54,7 +54,13 @@
* 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.
+ * @gpio_disable_free: free up GPIO muxing on a certain pin, the reverse of
+ * @gpio_request_enable
+ * @gpio_set_direction: Since controllers may need different configurations
+ * depending on whether the GPIO is configured as input or output,
+ * a direction selector function may be implemented as a backing
+ * to the GPIO controllers that need pin muxing.
*/
struct pinmux_ops {
int (*request) (struct pinctrl_dev *pctldev, unsigned offset);
@@ -76,11 +82,17 @@
void (*gpio_disable_free) (struct pinctrl_dev *pctldev,
struct pinctrl_gpio_range *range,
unsigned offset);
+ int (*gpio_set_direction) (struct pinctrl_dev *pctldev,
+ struct pinctrl_gpio_range *range,
+ unsigned offset,
+ bool input);
};
/* External interface to pinmux */
extern int pinmux_request_gpio(unsigned gpio);
extern void pinmux_free_gpio(unsigned gpio);
+extern int pinmux_gpio_direction_input(unsigned gpio);
+extern int pinmux_gpio_direction_output(unsigned gpio);
extern struct pinmux * __must_check pinmux_get(struct device *dev, const char *name);
extern void pinmux_put(struct pinmux *pmx);
extern int pinmux_enable(struct pinmux *pmx);
@@ -97,6 +109,16 @@
{
}
+static inline int pinmux_gpio_direction_input(unsigned gpio)
+{
+ return 0;
+}
+
+static inline int pinmux_gpio_direction_output(unsigned gpio)
+{
+ return 0;
+}
+
static inline struct pinmux * __must_check pinmux_get(struct device *dev, const char *name)
{
return NULL;