linux-kernel - Re: [PATCH v2] mmc: mmci: manage MMC_PM_KEEP

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Message-ID: <CAPDyKFq2Du1UWpvRFpVF_qL65SP0DfEV872U9Xe-9i7xKxXhqg@mail.gmail.com>
Date:   Mon, 14 Mar 2022 17:18:58 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Yann Gautier <yann.gautier@...s.st.com>
Cc:     linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        Christophe Kerello <christophe.kerello@...s.st.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Ludovic Barre <ludovic.barre@...s.st.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Russell King <linux@...linux.org.uk>,
        Marek Vasut <marex@...x.de>, kernel@...electronics.com,
        Manivannan Sadhasivam <mani@...nel.org>,
        Grzegorz Szymaszek <gszymaszek@...rt.pl>
Subject: Re: [PATCH v2] mmc: mmci: manage MMC_PM_KEEP_POWER per variant config

On Mon, 14 Mar 2022 at 15:34, Yann Gautier <yann.gautier@...s.st.com> wrote:
>
> On 3/14/22 14:03, Ulf Hansson wrote:
> > On Mon, 14 Mar 2022 at 13:56, Yann Gautier <yann.gautier@...s.st.com> wrote:
> >>
> >> Add a disable_keep_power field in variant_data struct. The
> >> MMC_PM_KEEP_POWER flag will be enabled if disable_keep_power is not set.
> >> It is only set to true for stm32_sdmmc variants.
> >>
> >> The issue was seen on STM32MP157C-DK2 board, which embeds a wifi chip.
> >> It doesn't correctly support low power on this board. The Wifi chip
> >> awaits an always-on regulator, but it was connected to v3v3 which is off
> >> in low-power sequence. MMC_PM_KEEP_POWER should then be disabled.
> >
> > Just to make sure I get this correct.
> >
> > Why can't the regulator stay on during system suspend? The point is,
> > we don't need an always on regulator to cope with this.
> >
> > Kind regards
> > Uffe
>
> Hi Ulf,
>
> This v3v3 regulator powers most of the devices on this board. So we need
> to switch it off to gain power in suspend mode.

I see. Thanks for sharing that information.

The MMC_PM_KEEP_POWER flag is there to describe what is supported by
the platform/host. It doesn't mean that the card *must* stay powered
on during system suspend. Instead that depends on whether system
wakeup for the SDIO/WiFi is supported too - and if that is enabled by
userspace. If not, the regulator will be turned off for the SDIO card
during system suspend.

Assuming the regulator is implemented as a proper regulator and can
remain on during system suspend, the right thing would be to keep the
MMC_PM_KEEP_POWER flag around.

Kind regards
Uffe

>
>
> Yann
>
> >
> >>
> >> The flag can still be enabled through DT property:
> >> keep-power-in-suspend.
> >>
> >> Signed-off-by: Yann Gautier <yann.gautier@...s.st.com>
> >> ---
> >> Update in v2:
> >> Reword commit message to better explain the issue.
> >>
> >> Resend the patch alone. It was previoulsy in a series [1] for which the
> >> other patches will be reworked.
> >>
> >> [1] https://lore.kernel.org/lkml/20220304135134.47827-1-yann.gautier@foss.st.com/
> >>
> >>   drivers/mmc/host/mmci.c | 5 ++++-
> >>   drivers/mmc/host/mmci.h | 1 +
> >>   2 files changed, 5 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> >> index 45b8608c935c..0e2f2f5d6a52 100644
> >> --- a/drivers/mmc/host/mmci.c
> >> +++ b/drivers/mmc/host/mmci.c
> >> @@ -274,6 +274,7 @@ static struct variant_data variant_stm32_sdmmc = {
> >>          .busy_detect            = true,
> >>          .busy_detect_flag       = MCI_STM32_BUSYD0,
> >>          .busy_detect_mask       = MCI_STM32_BUSYD0ENDMASK,
> >> +       .disable_keep_power     = true,
> >>          .init                   = sdmmc_variant_init,
> >>   };
> >>
> >> @@ -301,6 +302,7 @@ static struct variant_data variant_stm32_sdmmcv2 = {
> >>          .busy_detect            = true,
> >>          .busy_detect_flag       = MCI_STM32_BUSYD0,
> >>          .busy_detect_mask       = MCI_STM32_BUSYD0ENDMASK,
> >> +       .disable_keep_power     = true,
> >>          .init                   = sdmmc_variant_init,
> >>   };
> >>
> >> @@ -2172,7 +2174,8 @@ static int mmci_probe(struct amba_device *dev,
> >>          host->stop_abort.flags = MMC_RSP_R1B | MMC_CMD_AC;
> >>
> >>          /* We support these PM capabilities. */
> >> -       mmc->pm_caps |= MMC_PM_KEEP_POWER;
> >> +       if (!variant->disable_keep_power)
> >> +               mmc->pm_caps |= MMC_PM_KEEP_POWER;
> >>
> >>          /*
> >>           * We can do SGIO
> >> diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
> >> index e1a9b96a3396..2cad1ef9766a 100644
> >> --- a/drivers/mmc/host/mmci.h
> >> +++ b/drivers/mmc/host/mmci.h
> >> @@ -361,6 +361,7 @@ struct variant_data {
> >>          u32                     opendrain;
> >>          u8                      dma_lli:1;
> >>          u32                     stm32_idmabsize_mask;
> >> +       u8                      disable_keep_power:1;
> >>          void (*init)(struct mmci_host *host);
> >>   };
> >>
> >> --
> >> 2.25.1
> >>
>