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

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Date:   Mon, 14 Mar 2022 15:34:07 +0100
From:   Yann Gautier <yann.gautier@...s.st.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
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 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.


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
>>