Re: [PATCH v4 1/2] dt-bindings: mmc: Extend keep-power-in-suspend beyond SDIO

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The `keep-power-in-suspend` DT property contract is extended to (e)MMC devices but is not implemented in the MMC core, causing cards to be incorrectly powered off during suspend.
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--- Patch [1]: [PATCH v4 1/2] dt-bindings: mmc: Extend keep-power-in-suspend beyond SDIO ---
commit 586f6f073c6606f13ea85125ddb68d3d032283b3
Author: Kamal Dasu <kamal.dasu@broadcom.com>

dt-bindings: mmc: Extend keep-power-in-suspend beyond SDIO

This commit drops the SDIO only restriction for the keep-power-in-suspend
property and documents its use for MMC devices. This allows platforms where
firmware accesses the card directly during system resume to specify that
card power must be preserved.

> diff --git a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
> index 3d7195e9461c3..f4663b3184355 100644
> --- a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
> +++ b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
> @@ -291,7 +291,12 @@ properties:
>    keep-power-in-suspend:
>      $ref: /schemas/types.yaml#/definitions/flag
>      description:
> -      SDIO only. Preserves card power during a suspend/resume cycle.
> +      Preserves card power during a suspend/resume cycle. For SDIO,
> +      this is a request an individual function driver can make at
> +      runtime via sdio_set_host_pm_flags(). For (e)MMC, it is instead
> +      a fixed platform characteristic, needed on boards where firmware
> +      accesses the card directly during system resume, before the
> +      kernel's own resume path runs.

[Severity: High]
Does the MMC core currently support preserving power for MMC devices
during suspend to fulfill this newly documented contract?

Looking at the eMMC suspend path, it unconditionally calls mmc_power_off():

drivers/mmc/core/mmc.c:_mmc_suspend() {
	...
	if (!err) {
		mmc_power_off(host);
		mmc_card_set_suspended(host->card);
	}
	...
}

The SD suspend path also unconditionally powers off the card:

drivers/mmc/core/sd.c:_mmc_sd_suspend() {
	...
	if (!err) {
		mmc_power_off(host);
		mmc_card_set_suspended(card);
	}
	...
}

If a platform relies on this property because its firmware accesses the
card directly during resume, wouldn't unconditionally powering it off during
suspend break the system resume?

Is there a missing patch in this series to update the core to check
the property before calling mmc_power_off()?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260728190314.2325906-1-kamal.dasu@broadcom.com?part=1