[U-Boot] [PATCH v3 0/5] Add get_alt_function ops

[Patrice CHOTARD]

Hi Michal

On 09/11/2018 07:51 AM, Michal Simek wrote:
> On 10.9.2018 18:11, Patrice Chotard wrote:
>>
>> This series :
>>   - Add new gpio ops get_alt_function
>>   - Add get_function and get_alt_function support to stm32 gpio driver
>>   - Add get_alt_function test
> 
> 
> I went quickly over this series and TBH I am not getting what this is
> for. It looks like that this is the part of pinmux.
> 
> Can you please elaborate more what this is for?

Currently, get_function callback returns the state of a gpio
(GPIOF_INPUT, GPIOF_OUTPUT or GPIO_FUNC).

If a pin's state is GPIO_FUNC, it's useful to know which alternate
function is selected for debug purpose.

As example, on STM32 SoCs, a pins can be configured as GPIO or also
configured with up to 16 alternate function. Using command "gpio", user
can retrieve this information as shown below:

STM32MP> gpio state -a

Bank GPIOA:
GPIOA0: unused: 0 [ ]
GPIOA1: unused: 0 [ ]
GPIOA2: unused: 0 [ ]
GPIOA3: unused: 0 [ ]
GPIOA4: unused: 0 [ ]
GPIOA5: unused: 0 [ ]
GPIOA6: unused: 0 [ ]
GPIOA7: unused: 0 [ ]
GPIOA8: func: 9
GPIOA9: func: 10
GPIOA10: unused: 0 [ ]
GPIOA11: unused: 0 [ ]
GPIOA12: unused: 0 [ ]
GPIOA13: output: 1 [x] red.gpios
GPIOA14: output: 0 [x] green.gpios
GPIOA15: unused: 0 [ ]

It shows that pin 8 and 9 of bank A are configured respectively in
alternate function 9 and 10.

Patrice



> 
> Thanks,
> Michal
>