On Wed, 25 Aug 2021 at 16:34, Yann Gautier [off-list ref] wrote:

Hi,

In drivers/mmc/host/mmci.c, MMC_PM_KEEP_POWER is unconditionally enabled.
This prevents correct low-power sequence on STM32MP157C-DK2 board which
embeds a Wifi chip brcm,bcm4329-fmac (this wifi part has not yet been
sent upstream).

Exactly why doesn't this work with the STM32MP157C-DK2 board?

This MMC_PM_KEEP_POWER can be taken from DT with the property
keep-power-in-suspend. This is what is done for other MMC drivers.

The DT property is what should have been used for mmci as well.

I wonder what should be the best solution for this.

1) Remove MMC_PM_KEEP_POWER from the driver, and modify all SoC device
tree files embedding a arm,pl18x with adding keep-power-in-suspend;
property (except stm32mp151.dtsi file).
This can be easy to do (~10 files to modify). But that could be more
board dependent, if an SDIO chip is plugged on this MMC IP.
And the name keep-power-in-suspend can be misleading as it only applies
to SDIO.

2) Remove MMC_PM_KEEP_POWER from the driver, and modify board DT files
with the property. This could be a difficult task to find all those
boards. And this should be applied only for SDIO configs.

3) Just modify the driver to apply this capability for all MMCI chips
but STM32. This could be done in the dedicated file, in
sdmmc_variant_init() function. But some boards based on STM32MP15 chip
might want to keep this capability.

I would suggest option 3).

As a matter of fact, we also allow MMC_PM_KEEP_POWER to become set
when parsing the DTB via calling mmc_of_parse(). So just changing the
default value (don't set MMC_PM_KEEP_POWER) for the stm32 variant,
would do the trick I think.

Kind regards
Uffe