Re: [PATCH v3 1/2] dt-bindings: mmc: Document no-mmc-poweroff-suspend property

[Krzysztof Kozlowski <krzk@kernel.org>]

On 23/07/2026 21:24, Kamal Dasu wrote:
> On Thu, Jul 23, 2026 at 3:01 PM Krzysztof Kozlowski <krzk@kernel.org> wrote:
>>
>> On 23/07/2026 20:53, Kamal Dasu wrote:
>>> On Thu, Jul 23, 2026 at 3:51 AM Krzysztof Kozlowski <krzk@kernel.org> wrote:
>>>
>>>> On Wed, Jul 22, 2026 at 05:14:16PM -0400, Kamal Dasu wrote:
>>>>> On some platforms, firmware accesses the (e)MMC card directly during
>>>>> system resume from Suspend-to-DRAM, before the kernel's own resume
>>>>> path has run, in order to load boot code using hard wired logic that
>>>>> is not field updatable. This requires the card to remain powered
>>>>> and responsive throughout suspend: it cannot be put to sleep, sent a
>>>>> power-off notification, or have its supply removed.
>>>>>
>>>>> Add a no-mmc-poweroff-suspend flag property so affected boards can
>>>>> tell the mmc core to keep the card powered across suspend instead of
>>>>> sleeping or powering it off.
>>>>>
>>>>> Signed-off-by: Kamal Dasu <kamal.dasu@broadcom.com>
>>>>> ---
>>>>> Changes in v3:
>>>>>   - Renamed from no-mmc-sleep; dropped S_A_TIMEOUT framing per Ulf.
>>>>>
>>>>> Changes in v2:
>>>>>   - New patch, replacing v1's card-level quirk, per Ulf.
>>>>>
>>>>>  .../devicetree/bindings/mmc/mmc-controller-common.yaml | 10 ++++++++++
>>>>>  1 file changed, 10 insertions(+)
>>>>>
>>>>> diff --git
>>>> a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
>>>> b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
>>>>> index 3d7195e9461c..5f7b3f8ef1dd 100644
>>>>> --- a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
>>>>> +++ b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
>>>>> @@ -232,6 +232,16 @@ properties:
>>>>>      description:
>>>>>        All eMMC HS400 modes are not supported.
>>>>>
>>>>> +  no-mmc-poweroff-suspend:
>>>>> +    $ref: /schemas/types.yaml#/definitions/flag
>>>>> +    description:
>>>>> +      On this platform, firmware accesses the attached (e)MMC card
>>>>> +      directly during system resume, before the kernel's own resume
>>>>> +      path runs. The card must therefore stay powered throughout
>>>>> +      suspend, and the controller must not send it a sleep or
>>>>> +      power-off notification. The kernel re-initializes the card
>>>>> +      after resume, since firmware may have already reset it.
>>>>
>>>> Isn't this exactly the same as keep-power-in-suspend?
>>>>
>>>>
>>> Not quite, though I see why it reads that way from the description
>>> alone.
>>>
>>> keep-power-in-suspend only takes effect through host->pm_flags, which
>>> gets set at runtime via sdio_set_host_pm_flags() -- an SDIO function
>>> driver opts in from its own suspend() callback, per suspend cycle.
>>> The consuming logic lives entirely in mmc_sdio_suspend()/
>>> mmc_sdio_resume() (drivers/mmc/core/sdio.c); pm_flags is never read
>>> in mmc.c, which is what this series touches.
>>>
>>> no-mmc-poweroff-suspend differs in two ways:
>>>
>>>   - It's a fixed platform characteristic, not a per-driver runtime
>>>     request. There's no SDIO-style function driver to call an opt-in
>>>     API from for a plain (e)MMC storage card -- the requirement here
>>>     (firmware always touches the card at resume, on this board) is
>>>     always true, not something decided per suspend cycle.
>>>   - The resume-side behavior differs. keep-power-in-suspend without a
>>>     wake IRQ does nothing at resume: it assumes the card's state
>>>     survived untouched. This flag needs the opposite -- keep power,
>>>     but still fully re-initialize the card via mmc_init_card(), since
>>>     firmware may have reconfigured it while the kernel was suspended.
>>
>> All this is just driver stuff which I did not ask about.
>>
>> The property is described pretty the same - do not power off during
>> suspend/resume.
>>
> 
> Do you want me to fold this change into using 'keep-power-in-suspend'
> for mmc as well ?.

I don't want a new property if it has exactly the same meaning. Of
course I am happy to hear why the property has different meaning in
terms of hardware description. We do not talk here about drivers, obviously.

Best regards,
Krzysztof