Date:   Tue, 15 Mar 2022 10:07:03 +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 17:52, Yann Gautier <yann.gautier@...s.st.com> wrote:
>
> On 3/14/22 17:18, Ulf Hansson wrote:
> > 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
> >
>
> OK, but in the wifi driver we use on this platform (brcmfmac), the
> suspend/resume functions (brcmf_ops_sdio_suspend/brcmf_ops_sdio_resume)
> use the flag to check regu was off, and then call probe function during
> resume, to re-init Wifi chip and reload its firmware.

I had a closer look at the brcmfmac driver, thanks for the pointers.

In my opinion, I think we should change the brcmfmac driver, so it
decides to power off the SDIO card, unless the WiFi chip is configured
to serve us with system wakeups.

I can send a patch for brcmfmac that we can try, unless you want to
send it yourself?

>
>
> Best regards,
> Yann

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
> >>>>
> >>
>

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