[U-Boot] [Uboot-stm32] [PATCH v3 0/5] Add get_alt_function ops

[Michal Simek]

On 11.9.2018 15:31, Patrice CHOTARD wrote:
> On 09/11/2018 02:17 PM, Michal Simek wrote:
>> On 11.9.2018 13:12, Patrice CHOTARD wrote:
>>> Hi,
>>>
>>> On 09/11/2018 12:24 PM, Michal Simek wrote:
>>>> Hi,
>>>>
>>>> On 11.9.2018 09:31, Patrice CHOTARD wrote:
>>>>> 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.
>>>>
>>>> Can you list that functionality? Isn't it something what should be shown
>>>> with a name instead of number?
>>>
>>> Listing this functionality is possible and printing name instead of
>>> number also, but for each pins, alternate function configuration is
>>> different and need to store all these informations into a table, which
>>> consumes a lot of memory.
>>>
>>>> I expect that user has to go to any decode table to find out what 9 or
>>>> 10 means.
>>>
>>> Yes, using the SoC's datasheet, user can find the corresponding
>>> alternate function description.
>>
>> Can you give some examples of that functionality or link to datasheet
>> and page?
> 
> As example, regarding the pin 8 of bank A (GPIOA8 above), alternate
> function 9 means that pins is currently configured as SDMMC2_DATA4.
> 
> For this pins, here are all the possible alternate function :
> 	
> alternate function 	description
> 
> AF0 			MCO0
> AF1			TIM1_CH1
> AF2
> AF3			TIM8_BKIN2
> AF4			I2C3_SCL
> AF5			SPI3_MOSI/SDO
> AF6
> AF7			USART1_CK
> AF8			SDMMC2 CKIN
> AF9 			SDMMC2 DATA4
> AF10			USB_SOF
> AF11
> AF12			SAI4_SD_B
> AF13			UART7_RX
> AF14 			LCD_R6
> AF15 			EVENTOUT

ok that means that it is pin mux decoding and you want to use gpio
status command to show it. I would expect when you set a value for gpio
that nothing is going to change because it is not propagated to output pin.

I can do it for zynq/zynqmp device but I don't think this is something
what should be shown via gpio status command.
In my case there is even different address range which should be used to
get this value.

Anyway I think that it would be better to create regular pinctrl command
for this instead of trying to reuse gpio command for that but that's
just my opinion.

Thanks,
Michal