linux-kernel - Re: [PATCH v3 3/4] mmc: sdhci-tegra: Issue CMD and DAT resets together

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Message-ID: <91f09a39-57fa-06a9-6e9e-b3e768d9e26a@intel.com>
Date:   Mon, 26 Sep 2022 22:26:19 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Prathamesh Shete <pshete@...dia.com>, ulf.hansson@...aro.org,
        thierry.reding@...il.com, jonathanh@...dia.com,
        p.zabel@...gutronix.de, linux-mmc@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     anrao@...dia.com, smangipudi@...dia.com, kyarlagadda@...dia.com
Subject: Re: [PATCH v3 3/4] mmc: sdhci-tegra: Issue CMD and DAT resets
 together

On 26/09/22 12:49, Prathamesh Shete wrote:
> In case of error condition to avoid system crash
> Tegra SDMMC controller requires CMD and DAT resets
> issued together. SDHCI controller FSM goes into
> bad state due to rapid SD card hot-plug event.
> Issuing reset on the CMD FSM before DATA FSM results
> in kernel panic, hence add support to issue CMD and
> DAT resets together.
> This is applicable to Tegra186 and later chips.
> 
> Signed-off-by: Aniruddha TVS Rao <anrao@...dia.com>
> Signed-off-by: Prathamesh Shete <pshete@...dia.com>
> ---
>  drivers/mmc/host/sdhci-tegra.c |  3 ++-
>  drivers/mmc/host/sdhci.c       | 20 +++++++++++++++-----
>  drivers/mmc/host/sdhci.h       |  2 ++
>  3 files changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 4d32b5bfc424..58449e010a9b 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -1532,7 +1532,8 @@ static const struct sdhci_pltfm_data sdhci_tegra186_pdata = {
>  		  SDHCI_QUIRK_NO_HISPD_BIT |
>  		  SDHCI_QUIRK_BROKEN_ADMA_ZEROLEN_DESC |
>  		  SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN,
> -	.quirks2 = SDHCI_QUIRK2_PRESET_VALUE_BROKEN,
> +	.quirks2 = SDHCI_QUIRK2_PRESET_VALUE_BROKEN |
> +		   SDHCI_QUIRK2_ISSUE_CMD_DAT_RESET_TOGETHER,
>  	.ops  = &tegra186_sdhci_ops,
>  };
>  
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 7689ffec5ad1..2f4a0e84fee8 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -3060,12 +3060,22 @@ static bool sdhci_request_done(struct sdhci_host *host)
>  			host->ops->set_clock(host, host->clock);
>  
>  		/*
> -		 * Spec says we should do both at the same time, but Ricoh
> -		 * controllers do not like that.
> +		 * While the specification says we should do both at the
> +		 * same time, Ricoh controllers (and potentially others) do not
> +		 * like that. On the other hand, some controllers (such as those
> +		 * found on Tegra186 and later) rely on both being reset at the
> +		 * same time. Use a quirk for the latter category since most
> +		 * controllers seem to work fine with DAT and CMD getting reset
> +		 * at the same time.
>  		 */
> -		sdhci_do_reset(host, SDHCI_RESET_CMD);
> -		sdhci_do_reset(host, SDHCI_RESET_DATA);
> -
> +		if (host->quirks2 &
> +			SDHCI_QUIRK2_ISSUE_CMD_DAT_RESET_TOGETHER) {
> +			sdhci_do_reset(host, SDHCI_RESET_CMD |
> +					SDHCI_RESET_DATA);
> +		} else {
> +			sdhci_do_reset(host, SDHCI_RESET_CMD);
> +			sdhci_do_reset(host, SDHCI_RESET_DATA);
> +		}

There is a bit a tidy up of SDHCI resets here:

https://lore.kernel.org/linux-mmc/20220926192022.85660-1-adrian.hunter@intel.com/

Would you mind implementing the quirk on top of that patch set.
The quirk should go somewhere in the new sdhci_reset_for_reason()
function, which should make it's use more consistent.