Re: [PATCH] mmc: mmci: stm32: handle mmc power up

[Marek Vasut <marex@nabladev.com>]

On 11/13/26 5:53 PM, Christophe KERELLO wrote:
> Hello Ulf,
> 
> On 11/13/26 12:46, Ulf Hansson wrote:
>> On Thu, Nov 12, 2026 at 7:26 AM Marek Vasut <marex@nabladev.com> wrote:
>>> On 11/11/26 12:45 PM, Ulf Hansson wrote:
>>>
>>> Hello Ulf,
>>>
>>>>>>> -       if (ios.power_mode == MMC_POWER_OFF) {
>>>>>>> +       if (ios.power_mode == MMC_POWER_OFF ||
>>>>>>> +           ios.power_mode == MMC_POWER_UP) {
>>>>>>>                    /* Only a reset could power-off sdmmc */
>>>>>>>                    reset_control_assert(host->rst);
>>>>>>>                    udelay(2);
>>>>>> What exactly will this reset?
>>>>> The controller.
>>>> Okay, I see.
>>>>
>>>> In that case, this reset also makes us reset preceding updates to any
>>>> other registers, for example the clock register. I would not recommend
>>>> doing that here, but perhaps there is no better option.
>>> Does that pose a problem in the MMC_POWER_OFF/UP state ? I agree this
>>> would pose a problem in the MMC_POWER_ON state, but here the card is 
>>> not ON.
>> I think it is a problem, yes. If you have a closer look at what
>> happens in mmci_set_ios(), I think you will agree.
>>
>>>> If I may I suggest an alternative solution, perhaps we can manage this
>>>> in the ->runtime_resume() callback instead. If the power_mode ==
>>>> MMC_POWER_OFF, perhaps do this reset there instead? Would that work?
>> Can you try this?
> 
> I have sent a new patch based on your proposal:
> https://lore.kernel.org/linux-mmc/20261113-fix-resume-reset- 
> v1-1-115b3da5764d@foss.st.com/
> 
> It works fine on my side.
> 
> Hi Marek,
> Could you also test it on your board to confirm that it fixes the issue 
> you reported?
This works too, thanks .