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

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Date:   Mon, 31 Jul 2017 09:33:42 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Ludovic Desroches <ludovic.desroches@...rochip.com>,
        linux-mmc@...r.kernel.org
Cc:     ulf.hansson@...aro.org, linux-kernel@...r.kernel.org,
        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 26/07/17 17:02, Ludovic Desroches wrote:
> When the device is non removable, the card detect signal is often use

use -> used

> 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

defaut -> default

> 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>

Apart from spelling

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
>  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

resetted -> reset

> +	 * 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;
>