Messages in this thread | | | Date | Mon, 17 May 2021 15:57:13 -0700 | From | Drew Fustini <> | Subject | Re: [PATCH 1/2] pinctrl: core: configure pinmux from pins debug file |
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On Mon, May 17, 2021 at 11:02:00PM +0300, Andy Shevchenko wrote: > On Sun, May 16, 2021 at 7:43 PM Dario Binacchi <dariobin@libero.it> wrote: > > > > The MPUs of some architectures (e.g AM335x) must be in privileged > > operating mode to write on the pinmux > > pinmux is not pin configuration. You need to rethink the approach. > > > registers. In such cases, where > > writes will not work from user space, now it can be done from the pins > > debug file if the platform driver exports the pin_dbg_set() helper among > > the registered operations. > > Drew, is it similar to what you are trying to achieve?
Yes, I would say this similar to what I was trying to accomplish: being able to change contents of conf_<module>_<pin> register [table 9-60] from userspace.
However, I was specifically looking to change bits 2:0 which is mux mode. My motivation was to allow BeagleBone users to easily switch between pin functions on the expansion headers during runtime to make rapid prototyping with a breadboard easier (such as changing header pin from GPIO to SPI mode). Most of the header pins have 7 different modes.
Ultimately, the solution I settled on with feedback from this list was to create pinmux-select debugfs file that can activate desired fucntion: 6199f6becc86 ("pinctrl: pinmux: Add pinmux-select debugfs file")
Bits 6:3 are related to what this subsystem would refer to as pin conf such as slew, input enable and bias. Thus it might make sense to expose something like a select-pinconf file to activate pin conf settings from userspace. This would require using 'pinconf-single' compatible.
I fixed pinctrl-single bug regarding pinconf last year so it should be possible to use 'pinconf-single' compatible for the am33xx_pinmux node: f46fe79ff1b6 ("pinctrl-single: fix pcs_parse_pinconf() return value")
Thanks, Drew
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