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

[Kamal Dasu]

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.

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>

Regards

Kamal

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