linux-kernel - Re: [PATCH] mmc: sdhci-of-at91: wait for calibration done before proceed

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Date:   Thu, 23 Sep 2021 12:02:48 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>,
        eugen.hristev@...rochip.com, ulf.hansson@...aro.org,
        nicolas.ferre@...rochip.com, alexandre.belloni@...tlin.com,
        ludovic.desroches@...rochip.com
Cc:     linux-mmc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: sdhci-of-at91: wait for calibration done before
 proceed

On 15/09/21 1:28 pm, Claudiu Beznea wrote:
> Datasheet specifies that at the end of calibration the SDMMC_CALCR_EN
> bit will be cleared. No commands should be send before calibration is
> done.
> 
> Fixes: dbdea70f71d67 ("mmc: sdhci-of-at91: fix CALCR register being rewritten")
> Fixes: 727d836a375ad ("mmc: sdhci-of-at91: add DT property to enable calibration on full reset")
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
> ---
>  drivers/mmc/host/sdhci-of-at91.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
> index 5564d7b23e7c..2b28711e039d 100644
> --- a/drivers/mmc/host/sdhci-of-at91.c
> +++ b/drivers/mmc/host/sdhci-of-at91.c
> @@ -114,6 +114,8 @@ static void sdhci_at91_reset(struct sdhci_host *host, u8 mask)
>  {
>  	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>  	struct sdhci_at91_priv *priv = sdhci_pltfm_priv(pltfm_host);
> +	unsigned long timeout = jiffies + msecs_to_jiffies(20);
> +	unsigned int tmp;
>  
>  	sdhci_reset(host, mask);
>  
> @@ -126,6 +128,14 @@ static void sdhci_at91_reset(struct sdhci_host *host, u8 mask)
>  
>  		sdhci_writel(host, calcr | SDMMC_CALCR_ALWYSON | SDMMC_CALCR_EN,
>  			     SDMMC_CALCR);
> +
> +		do {
> +			tmp = sdhci_readl(host, SDMMC_CALCR);
> +		} while (time_before(jiffies, timeout) &&
> +			 (tmp & SDMMC_CALCR_EN));
> +
> +		if (tmp & SDMMC_CALCR_EN)
> +			dev_err(mmc_dev(host->mmc), "Failed to calibrate\n");

Please use a polling macro (include <linux/iopoll.h>)
i.e.

		if (read_poll_timeout(sdhci_readl, tmp, !(tmp & SDMMC_CALCR_EN),
				      10, 20000, false, host, SDMMC_CALCR))
			dev_err(mmc_dev(host->mmc), "Failed to calibrate\n");



>  	}
>  }
>  
>