Re: [PATCH 0/4] stm32mp: add minimal RCC support for STM32MP13

[Sean Anderson <seanga2@gmail.com>]

Hi Patrick,

On 5/17/22 4:12 AM, Patrick DELAUNAY wrote:
> Hi,
> 
> On 5/11/22 18:44, Sean Anderson wrote:
>> Hi Patrick,
>>
>> On 5/10/22 3:51 AM, Patrick Delaunay wrote:
>>>
>>> Add a minimal support for STM32MP13 RCC, the reset and clock controller
>>> - update of the RCC MISC driver to bind the correct clock and reset driver
>>> - reset driver, same than STM32MP15x = drivers/reset/stm32-reset.c
>>> - clock driver, add a empty driver for STM32MP13x =
>>>    drivers/clk/stm32/clk-stm32mp13.c
>>> - Add RCC node in SOC device tree with u-boot,dm-pre-reloc property
>>>
>>> This serie is only a preliminary step for STM32MP13 clock and reset support
>>> in U-Boot, based on Linux kernel binding introduced by [1] and it prepares
>>> the next device tree alignment with Linux kernel.
>>>
>>> The functional STMP13 clock driver based on CCF and on SCMI clocks
>>> provided by OP-TEE and the clock and reset references in SOC device tree
>>> will be pushed when the associated patches in [1] will be accepted.
>>>
>>> [1] Introduction of STM32MP13 RCC driver (Reset Clock Controller)
>>> https://lore.kernel.org/linux-arm-kernel/20220316131000.9874-1-gabriel.fernandez@foss.st.com/
>>
>> I'm not really sure what the purpose of this series is. Can you
>> elaborate a bit on why we need a dummy clock driver? Why don't
>> you just add the binding to the device tree without the associated
>> driver?
> 
> 
> After this serie, the RCC reset part is functional on STM32MP13 (probe and ops)
> 
> even if the associated binding is not present in device tree.
> 
> tested with:
> 
> ------------------------- arch/arm/dts/stm32mp131.dtsi -------------------------
> index fcb0af09b5..d9c6185bcf 100644
> @@ -197,6 +197,7 @@
>               interrupt-names = "cmd_irq";
>               clocks = <&clk_pll4_p>;
>               clock-names = "apb_pclk";
> +            resets = <&rcc 14224>;
>               cap-sd-highspeed;
>               cap-mmc-highspeed;
>               max-frequency = <130000000>;
> 
> 
> A dummy STM32MP13 clock driver is requested to allow RCC MISC and RCC RESET
> 
> binding and probe without issue.

Shouldn't the solution be to make the clock optional in the user?

> This reset support was requested by SDMCC driver and SD-Card boot, before the patch:
> 
> http://patchwork.ozlabs.org/project/uboot/patch/20220506160540.13.I39b69e8dc7b43b8e265e77388fb53f7c1fa2a007@changeid/
> 
> 
> As we solve the SDMCC dependency issue (reset become optionnal), so this serie is no more mandatory.
> 
> 
> This serie is a just a cleanup / preliminary step, but I can drop this dummy RCC driver if it is disturbing.
I would like that, since this is not mandatory.

--Sean