This is a revised version of my previous RFC[1]. Although I modified the commits to make them look SCMI-independent, they are still posted as RFC because I have never tested them on real hardware. (background) I'm currently working on implementing SCMI pinctrl/gpio drivers on U-Boot[2]. Although the pinctrl driver for the kernel[3] was submitted by EPAM, it doesn't contain the gpio driver and I believe that we should discuss a couple of points on the kernel side to finalize my design for U-Boot. So this RFC is intended for reviews, especially to raise some issues. 1) how to obtain a value on an input pin All the existing gpio drivers are set to obtain a value on an input pin by accessing the hardware directly. In SCMI case, however, this is just impossible in its nature and must be supported via a protocol using "Input-value" configuration type. (See the spec[4], table-23.) The current pinconf framework is missing the feature (the pinconf parameter and a helper function). See patch#1, #2 and #3. Please note that there is an issue around the pin configuration in EPAM's current pinctrl driver as I commented[5]. 2) DT bindings I would like to propose a generic binding for pinctrl based gpio driver. This allows a "consumer" driver to handle gpio pins like as other normal gpio controllers support. (patch#5) 3) generic GPIO driver Based on (2), I tried to prototype a generic driver in patch#4. Thanks to a set of existing pinctrl_gpio helper functions, except (1), It seems that the driver can be implemented not relying on pin controller specific code, at least for SCMI pinctrl. I will appreciate any comments. -Takahiro Akashi [1] https://lkml.iu.edu//hypermail/linux/kernel/2310.0/00362.html [2] https://lists.denx.de/pipermail/u-boot/2023-September/529765.html [3] https://lkml.iu.edu/hypermail/linux/kernel/2308.1/01082.html [4] https://developer.arm.com/documentation/den0056/ [5] https://lkml.iu.edu/hypermail/linux/kernel/2308.2/07483.html AKASHI Takahiro (5): pinctrl: define PIN_CONFIG_INPUT pinctrl: always export pin_config_get_for_pin() pinctrl: add pinctrl_gpio_get_config() gpio: add pinctrl based generic gpio driver dt-bindings: gpio: Add bindings for pinctrl based generic gpio driver .../bindings/gpio/pin-control-gpio.yaml | 55 ++++++ drivers/gpio/Kconfig | 7 + drivers/gpio/Makefile | 1 + drivers/gpio/gpio-by-pinctrl.c | 165 ++++++++++++++++++ drivers/pinctrl/core.c | 19 ++ drivers/pinctrl/pinconf.h | 10 +- include/linux/pinctrl/consumer.h | 8 + include/linux/pinctrl/pinconf-generic.h | 5 + 8 files changed, 268 insertions(+), 2 deletions(-) create mode 100644 Documentation/devicetree/bindings/gpio/pin-control-gpio.yaml create mode 100644 drivers/gpio/gpio-by-pinctrl.c -- 2.34.1
