Re: [PATCH v10 0/6] mmc: core: Keep the card powered across suspend when firmware needs it live

[Ulf Hansson]

On Tue, Oct 27, 2026 at 8:53 PM Kamal Dasu <kamal.dasu@xxxxxxxxxxxx> wrote:
>
> On Tue, Oct 27, 2026 at 10:41 AM Ulf Hansson
> <ulf.hansson@xxxxxxxxxxxxxxxx> wrote:
> >
> > Background: on brcmstb boards with a Kioxia 016G01 eMMC, firmware accesses the
> > card directly during resume from Suspend-to-DRAM, before the kernel's own
> > resume path runs, in order to load boot code using hard wired logic that is not
> > field updatable. The card needs to stay powered and responsive for that access
> > to succeed, and since it is never power-cycled, it also needs to be reset
> > before the kernel reuses it after resume.
> >
> > Changes in v10:
> >         - To help out with the implementation I offered my help to try to move
> >         this forward.
> >         - The DT patches are good to go so I included them from the previous
> >         versions.
> >         - Patch 3 to 6 are new, but based on the work done by Kamal Dasu.
> >         - This is completely untested from my side, please help to test it.
> >
> > Kind regards
> > Ulf Hansson
> >
> >
> > Kamal Dasu (2):
> >   dt-bindings: mmc: Extend keep-power-in-suspend beyond SDIO
> >   dt-bindings: mmc: Add reset-card-at-resume property
> >
> > Ulf Hansson (4):
> >   mmc: core: Add option to keep an eMMC powered on at system suspend
> >   mmc: core: Split sdio_set_host_pm_flags()
> >   mmc: core: Move reset functions for eMMC
> >   mmc: core: Add support for resetting an eMMC at system resume
> >
> >  .../bindings/mmc/mmc-controller-common.yaml   | 10 +-
> >  drivers/mmc/core/core.c                       |  9 ++
> >  drivers/mmc/core/core.h                       |  1 +
> >  drivers/mmc/core/host.c                       | 10 ++
> >  drivers/mmc/core/mmc.c                        | 95 ++++++++++++-------
> >  drivers/mmc/core/sdio_io.c                    |  7 +-
> >  include/linux/mmc/host.h                      |  1 +
> >  7 files changed, 92 insertions(+), 41 deletions(-)
> >
> > --
> > 2.43.0
> >
>
> Hi Ulf,
>
> Test results for this series on a Broadcom STB board with the Kioxia
> 016G01 eMMC,
> which reproduces the problem during S3 suspend/resume with two DT variables:
>
>   keep-power-in-suspend  reset-card-at-resume  Result
>                             no                     no
>   enters suspend, board resets
>
>       at resume
>                             yes                    no
>   enters suspend, board resets
>
>        at resume
>                             no                     yes
>   suspend aborts, -EINVAL
>                             yes                    yes
>   s3 suspend/resume works
>
> Changes applied to Kernel: v7.3 + 7.4 merge window (linus/master
> d135ab453a74) with this
> series, plus the one-line fix I'm sending in reply to patch 6/6
> (details in my reply to that patch):
> mmc_resume() calls _mmc_hw_reset() without claiming the host, which
> triggers WARN_ON(!host->claimed) for every command sent during the
> reset. Claiming the host around the reset removes the warnings..
>
> The -EINVAL in the third row comes from mmc_host_class_prepare(), since
> MMC_PM_KEEP_POWER is not in pm_caps without keep-power-in-suspend.

Yes, that was actually intentional as we can't allow the system to
suspend in this configuration, as we may not wake up correctly, right?

Although, perhaps we should also log a warning earlier during the
probe of the host, when we are parsing the DT properties for it. To
upfront say something isn't correct.

>
> In the working case I also checked the md5sum of the first 5 MiB of
> /dev/mmcblk1 before and after suspend, and it is unchanged.
>
> With the fix applied:
> Tested-by: Kamal Dasu <kamal.dasu@xxxxxxxxxxxx>

Thanks and thanks for the fix on top!

>
> Regards
>
> Kamal

I will send a new version shortly to address the comments and needed fixes.

Kind regards
Uffe