linux-kernel - Re: [PATCH] mmc: sdhci-of-at91: force card detect value for non removable devices

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Date:   Thu, 3 Aug 2017 12:51:00 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Ludovic Desroches <ludovic.desroches@...rochip.com>
Cc:     "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        nicolas.ferre@...rochip.com
Subject: Re: [PATCH] mmc: sdhci-of-at91: force card detect value for non
 removable devices

On 26 July 2017 at 16:02, Ludovic Desroches
<ludovic.desroches@...rochip.com> wrote:
> When the device is non removable, the card detect signal is often use
> for another purpose i.e. muxed to another SoC peripheral or used as a
> GPIO. It could lead to wrong behaviors depending the defaut value of
> this signal if not muxed to the SDHCI controller.
>
> Fixes: bb5f8ea4d514 ("mmc: sdhci-of-at91: introduce driver for the Atmel SDMMC")
> Signed-off-by: Ludovic Desroches <ludovic.desroches@...rochip.com>

Thanks, applied for fixes and added a stable tag.

I also fixed some spellings according to the comments from Adrian.

Kind regards
Uffe

> ---
>  drivers/mmc/host/sdhci-of-at91.c | 36 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 35 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
> index 88e9b5f35a62..6a389f35396e 100644
> --- a/drivers/mmc/host/sdhci-of-at91.c
> +++ b/drivers/mmc/host/sdhci-of-at91.c
> @@ -31,6 +31,7 @@
>
>  #define SDMMC_MC1R     0x204
>  #define                SDMMC_MC1R_DDR          BIT(3)
> +#define                SDMMC_MC1R_FCD          BIT(7)
>  #define SDMMC_CACR     0x230
>  #define                SDMMC_CACR_CAPWREN      BIT(0)
>  #define                SDMMC_CACR_KEY          (0x46 << 8)
> @@ -44,6 +45,15 @@ struct sdhci_at91_priv {
>         bool restore_needed;
>  };
>
> +static void sdhci_at91_set_force_card_detect(struct sdhci_host *host)
> +{
> +       u8 mc1r;
> +
> +       mc1r = readb(host->ioaddr + SDMMC_MC1R);
> +       mc1r |= SDMMC_MC1R_FCD;
> +       writeb(mc1r, host->ioaddr + SDMMC_MC1R);
> +}
> +
>  static void sdhci_at91_set_clock(struct sdhci_host *host, unsigned int clock)
>  {
>         u16 clk;
> @@ -111,10 +121,18 @@ void sdhci_at91_set_uhs_signaling(struct sdhci_host *host, unsigned int timing)
>         sdhci_set_uhs_signaling(host, timing);
>  }
>
> +static void sdhci_at91_reset(struct sdhci_host *host, u8 mask)
> +{
> +       sdhci_reset(host, mask);
> +
> +       if (host->mmc->caps & MMC_CAP_NONREMOVABLE)
> +               sdhci_at91_set_force_card_detect(host);
> +}
> +
>  static const struct sdhci_ops sdhci_at91_sama5d2_ops = {
>         .set_clock              = sdhci_at91_set_clock,
>         .set_bus_width          = sdhci_set_bus_width,
> -       .reset                  = sdhci_reset,
> +       .reset                  = sdhci_at91_reset,
>         .set_uhs_signaling      = sdhci_at91_set_uhs_signaling,
>         .set_power              = sdhci_at91_set_power,
>  };
> @@ -369,6 +387,22 @@ static int sdhci_at91_probe(struct platform_device *pdev)
>                 host->quirks &= ~SDHCI_QUIRK_BROKEN_CARD_DETECTION;
>         }
>
> +       /*
> +        * If the device attached to the MMC bus is not removable, it is safer
> +        * to set the Force Card Detect bit. People often don't connect the
> +        * card detect signal and use this pin for another purpose. If the card
> +        * detect pin is not muxed to SDHCI controller, a default value is
> +        * used. This value can be different from a SoC revision to another
> +        * one. Problems come when this default value is not card present. To
> +        * avoid this case, if the device is non removable then the card
> +        * detection procedure using the SDMCC_CD signal is bypassed.
> +        * This bit is resetted when a software reset for all command is
> +        * performed so we need to implement our own reset function to set back
> +        * this bit.
> +        */
> +       if (host->mmc->caps & MMC_CAP_NONREMOVABLE)
> +               sdhci_at91_set_force_card_detect(host);
> +
>         pm_runtime_put_autosuspend(&pdev->dev);
>
>         return 0;
> --
> 2.12.2
>