Re: [PATCH 2/2] mmc: sdhci-esdhc-imx: disable the CMD CRC check for standard tuning

From: Ulf Hansson <ulf.hansson@linaro.org>
To: Haibo Chen <haibo.chen@nxp.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>,
	"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
	dl-linux-imx <linux-imx@nxp.com>, Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Sascha Hauer <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	Aisheng Dong <aisheng.dong@nxp.com>,
	Yangbo Lu <yangbo.lu@nxp.com>
Subject: Re: [PATCH 2/2] mmc: sdhci-esdhc-imx: disable the CMD CRC check for standard tuning
Date: Thu, 28 May 2020 12:14:40 +0200	[thread overview]
Message-ID: <CAPDyKFoSSS0rh06Kso44J+ZFQC16K+Xttw6gQfUiganHKG5BXg@mail.gmail.com> (raw)
In-Reply-To: <1590488522-9292-2-git-send-email-haibo.chen@nxp.com>

On Tue, 26 May 2020 at 12:32, <haibo.chen@nxp.com> wrote:
>
> From: Haibo Chen <haibo.chen@nxp.com>
>
> In current code, we add 1ms dealy after each tuning command for standard
> tuning method. Adding this 1ms dealy is because USDHC default check the
> CMD CRC and DATA line. If detect the CMD CRC, USDHC standard tuning
> IC logic do not wait for the tuning data sending out by the card, trigger
> the buffer read ready interrupt immediately, and step to next cycle. So
> when next time the new tuning command send out by USDHC, card may still
> not send out the tuning data of the upper command，then some eMMC cards
> may stuck, can't response to any command, block the whole tuning procedure.
>
> If do not check the CMD CRC for tuning, then do not has this issue. USDHC
> will wait for the tuning data of each tuning command and check them. If the
> tuning data pass the check, it also means the CMD line also okay for tuning.
>
> So this patch disable the CMD CRC check for tuning, save some time for the
> whole tuning procedure.
>
> Signed-off-by: Haibo Chen <haibo.chen@nxp.com>

Applied for next, thanks!

Kind regards
Uffe

> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index 2cf7fa59270e..b0ddf3db440f 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -91,6 +91,7 @@
>  /* NOTE: the minimum valid tuning start tap for mx6sl is 1 */
>  #define ESDHC_TUNING_START_TAP_DEFAULT 0x1
>  #define ESDHC_TUNING_START_TAP_MASK    0x7f
> +#define ESDHC_TUNING_CMD_CRC_CHECK_DISABLE     (1 << 7)
>  #define ESDHC_TUNING_STEP_MASK         0x00070000
>  #define ESDHC_TUNING_STEP_SHIFT                16
>
> @@ -1316,6 +1317,18 @@ static void sdhci_esdhc_imx_hwinit(struct sdhci_host *host)
>                                 tmp |= imx_data->boarddata.tuning_step
>                                         << ESDHC_TUNING_STEP_SHIFT;
>                         }
> +
> +                       /* Disable the CMD CRC check for tuning, if not, need to
> +                        * add some delay after every tuning command, because
> +                        * hardware standard tuning logic will directly go to next
> +                        * step once it detect the CMD CRC error, will not wait for
> +                        * the card side to finally send out the tuning data, trigger
> +                        * the buffer read ready interrupt immediately. If usdhc send
> +                        * the next tuning command some eMMC card will stuck, can't
> +                        * response, block the tuning procedure or the first command
> +                        * after the whole tuning procedure always can't get any response.
> +                        */
> +                        tmp |= ESDHC_TUNING_CMD_CRC_CHECK_DISABLE;
>                         writel(tmp, host->ioaddr + ESDHC_TUNING_CTRL);
>                 } else if (imx_data->socdata->flags & ESDHC_FLAG_MAN_TUNING) {
>                         /*
> @@ -1661,8 +1674,6 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev)
>         if (err)
>                 goto disable_ahb_clk;
>
> -       host->tuning_delay = 1;
> -
>         sdhci_esdhc_imx_hwinit(host);
>
>         err = sdhci_add_host(host);
> --
> 2.17.1
>