linux-kernel - Re: [PATCH 3/3] mmc: sdhci: Modify sdhci o2 quirk for eMMC HS200 tuning case

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Date:   Tue, 19 Dec 2017 10:37:13 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     LinuxPatchCommit <LinuxPatchCommit@...hubtech.com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "Shirley Her (SC)" <shirley.her@...hubtech.com>
Subject: Re: [PATCH 3/3] mmc: sdhci: Modify sdhci o2 quirk for eMMC HS200
 tuning case

On 04/12/17 12:10, LinuxPatchCommit wrote:
> Dear all,
> 
> Don't clear transfer mode register in sdhci_set_transfer_mode().
> 
> In sdhci_set_transfer_mode(), clear transfer mode quirk2 will clear SD host transfer mode register for non-data commands. This quirk is used for the bug of O2micro/Bayhubtech devices. In eMMC HS200 tuning case, the tuning process uses hardware tuning and it needs to set transfer mode register for tuning command.
> 
> Signed-off-by: ernest.zhang <ernest.zhang@...hubtech.com>
> ---
>  drivers/mmc/host/sdhci.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index 0d5fcca18c9e..d5b19fc9ea56 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -918,7 +918,9 @@ static void sdhci_set_transfer_mode(struct sdhci_host *host,
>  	if (data == NULL) {
>  		if (host->quirks2 &
>  			SDHCI_QUIRK2_CLEAR_TRANSFERMODE_REG_BEFORE_CMD) {
> -			sdhci_writew(host, 0x0, SDHCI_TRANSFER_MODE);
> +			/* cannot clear transfer mode register when tuning */
> +			if (cmd->opcode != MMC_SEND_TUNING_BLOCK_HS200)
> +				sdhci_writew(host, 0x0, SDHCI_TRANSFER_MODE);

In the HS200 case you are sending the tuning command with data, so I do not
understand why you need this i.e. you will never get here

>  		} else {
>  		/* clear Auto CMD settings for no data CMDs */
>  			mode = sdhci_readw(host, SDHCI_TRANSFER_MODE);
> --
> 2.14.1
>