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

[Kamal Dasu]

On Thu, Jul 23, 2026 at 3:01 PM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote:
>
> On 23/07/2026 20:53, Kamal Dasu wrote:
> > On Thu, Jul 23, 2026 at 3:51 AM Krzysztof Kozlowski <krzk@xxxxxxxxxx> 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@xxxxxxxxxxxx>
> >>> ---
> >>> 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 ?.

>
>
>
> Best regards,
> Krzysztof

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