linux-kernel - Re: [PATCH 08/11] mmc: core: Parse the SD SCR register for support of CMD48/49 and CMD58/59

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Date:   Fri, 7 May 2021 09:58:24 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>, linux-mmc@...r.kernel.org,
        Adrian Hunter <adrian.hunter@...el.com>
Cc:     shawn.lin@...k-chips.com, Linus Walleij <linus.walleij@...aro.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Avri Altman <avri.altman@....com>,
        Masami Hiramatsu <masami.hiramatsu@...aro.org>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/11] mmc: core: Parse the SD SCR register for support of
 CMD48/49 and CMD58/59


On 2021/5/5 0:12, Ulf Hansson wrote:
> In SD spec v4.x the support for CMD48/49 and CMD58/59 were introduced as
> optional features. To let the card announce whether it supports the
> commands, the SCR register has been extended with corresponding support
> bits. Let's parse and store this information for later use.
> 

Just check v4.0 spec, and it says

"Table 4-32 is added in Version 4.00. These commands are reserved for
future extenstion". So,

Reviewed-by: Shawn Lin <shawn.lin@...k-chips.com>

> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> ---
>   drivers/mmc/core/sd.c    | 4 +++-
>   include/linux/mmc/card.h | 2 ++
>   2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index 2c48d6504101..de7b5f8df550 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -222,7 +222,9 @@ static int mmc_decode_scr(struct mmc_card *card)
>   	else
>   		card->erased_byte = 0x0;
>   
> -	if (scr->sda_spec3)
> +	if (scr->sda_spec4)
> +		scr->cmds = UNSTUFF_BITS(resp, 32, 4);
> +	else if (scr->sda_spec3)
>   		scr->cmds = UNSTUFF_BITS(resp, 32, 2);
>   
>   	/* SD Spec says: any SD Card shall set at least bits 0 and 2 */
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index f9ad35dd6012..858fc4d11240 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -139,6 +139,8 @@ struct sd_scr {
>   	unsigned char		cmds;
>   #define SD_SCR_CMD20_SUPPORT   (1<<0)
>   #define SD_SCR_CMD23_SUPPORT   (1<<1)
> +#define SD_SCR_CMD48_SUPPORT   (1<<2)
> +#define SD_SCR_CMD58_SUPPORT   (1<<3)
>   };
>   
>   struct sd_ssr {
>