From 542e704f3ffee1dc4539c9e8191e4dc215220f5e Mon Sep 17 00:00:00 2001 From: Linus Walleij Date: Mon, 14 Nov 2011 10:06:22 +0100 Subject: 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 Acked-by: Stephen Warren Reviewed-by: Thomas Abraham Signed-off-by: Linus Walleij --- Documentation/pinctrl.txt | 32 ++++++++++++++++++++++++-------- 1 file changed, 24 insertions(+), 8 deletions(-) (limited to 'Documentation/pinctrl.txt') diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt index 43ba411d1571..3846264c5973 100644 --- a/Documentation/pinctrl.txt +++ b/Documentation/pinctrl.txt @@ -645,6 +645,17 @@ 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_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 @@ 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. -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 -- cgit