linux-kernel - Re: [PATCH] mmc: Fix force card detect in sdhci

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Message-ID: <CAKmtTBYquiYQ-=MVWCqH8=iiFONvt6B_==EZhWsQkSA8WNuYUQ@mail.gmail.com>
Date:   Sat, 23 Sep 2023 16:23:16 +0200
From:   Mathieu Moneyron <mathieu.moneyron@...il.com>
To:     Aubin Constans <aubin.constans@...rochip.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Eugen Hristev <eugen.hristev@...labora.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        linux-mmc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: Fix force card detect in sdhci

Hi Aubin,

Thanks for your feedback.
I'll try my best to give clear explanations.

On Sat, Sep 23, 2023 at 2:44 PM Aubin Constans
<aubin.constans@...rochip.com> wrote:
>
> On 04/09/2023 09:38, Adrian Hunter wrote:
> > + Eugen Hristev  > > On 30/08/23 12:23, mathieu wrote: >> On the ATMEL at91 when using
> the non-removable flag in device tree >> and not using the card-detect
> pin inside the device-tree pinctrl, >> the card detect pin is physically
> still used which can cause >> unknown behaviour when this pin is used
> for other purposes.
> Hi Mathieu,
>
> On which SoC(s) exactly, has this behaviour been observed?

This has been observed on SAMA5D27.
>
>
> Also, has this issue been discussed in any separate support request, in such
> case we could retrieve some background from it?
>
> By "unknown behaviour", do you mean "the card insertion status would
> follow whatever electrical level is seen on the card-detect pin"?

For instance our board design has the PA13 (card detect) pin wired to drive a
3v3 power supply.
The fixed regulator driver configure this pin as output (described in the device
tree).
But what I observed is that the sdmmc driver still want to use PA13 as the card
detect signal which is then configured as an input. This cause the 3v3 power to
drop.

By "unknown behavior" I mean the configuration of this pin as card detect sets
unwanted electrical levels to what's connected to this pin.
>
>
> >>  >> From my interpretation this seems to be caused by a hardware design
>  >> flaw and the real hardware is not working as intended by the >>
> documentation. >>
> >>
> >> Signed-off-by: Mathieu Moneyron <mathieu.moneyron@...il.com>
> >>
> >> ---
> >>  drivers/mmc/host/sdhci-of-at91.c | 5 +++++
> >>  1 file changed, 5 insertions(+)
> >>
> >> diff --git a/drivers/mmc/host/sdhci-of-at91.c
> >> b/drivers/mmc/host/sdhci-of-at91.c
> >> index 69fef88e7..4fd6bfbf6 100644
> >> --- a/drivers/mmc/host/sdhci-of-at91.c
> >> +++ b/drivers/mmc/host/sdhci-of-at91.c
> >> @@ -51,10 +51,15 @@ struct sdhci_at91_priv {
> >>  static void sdhci_at91_set_force_card_detect(struct sdhci_host *host)
> >>  {
> >>      u8 mc1r;
> >> +    u8 ctrl;
> >>
> >>      mc1r = readb(host->ioaddr + SDMMC_MC1R);
> >>      mc1r |= SDMMC_MC1R_FCD;
> >>      writeb(mc1r, host->ioaddr + SDMMC_MC1R);
> >> +
> >> +    ctrl = readb(host->ioaddr + SDHCI_HOST_CONTROL);
> >> +    ctrl |= SDHCI_CTRL_CDTEST_INS | SDHCI_CTRL_CDTEST_EN;
> >> +    writeb(ctrl, host->ioaddr + SDHCI_HOST_CONTROL);
> >>  }
> >>
> >>  static void sdhci_at91_set_clock(struct sdhci_host *host, unsigned
> >> int clock)
>
> Kind regards,
> Aubin
>
Kind regards,
Mathieu