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.
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
* 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;
*/
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
/**
* 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;
if (!function)
return -EINVAL;
- ret = pin_request(pctldev, pin, function, range);
+ ret = pin_request(pctldev, pin, function, range, direction);
if (ret < 0)
kfree(function);
/**
* 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)
{
/* 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 "
* 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);
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);
#else /* !CONFIG_PINMUX */
-static inline int pinmux_request_gpio(unsigned gpio)
+static inline int pinmux_request_gpio(unsigned gpio, bool direction)
{
return 0;
}
projects / karo-tx-linux.git / commitdiff