linux-kernel - Re: [PATCH V4] mmc: core: improve reasonableness of bus width setting for HS400es

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Message-ID: <CAPDyKFoEsRz8eQmZ+qXOSZ=cF2pjsR5UYJHp9UgJ4-3b6ofcww@mail.gmail.com>
Date:   Mon, 30 Jul 2018 17:06:10 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Hongjie Fang <hongjiefang@...micro.com>
Cc:     Shawn Lin <shawn.lin@...k-chips.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Bastian Stender <bst@...gutronix.de>,
        Chanho Min <chanho.min@....com>,
        Kyle Roeschley <kyle.roeschley@...com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4] mmc: core: improve reasonableness of bus width setting
 for HS400es

On 17 July 2018 at 11:14, Hongjie Fang <hongjiefang@...micro.com> wrote:
> mmc_select_hs400es() calls mmc_select_bus_width() which will continue
> to set 4bit transfer mode if fail to set 8bit mode. The bus width
> should not be set to 4bit in HS400es.
>
> When fail to set 8bit mode, need return error directly for HS400es.
>
> Signed-off-by: Hongjie Fang <hongjiefang@...micro.com>
> ---
>  drivers/mmc/core/mmc.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 4466f5d..0dbc512 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1338,8 +1338,12 @@ static int mmc_select_hs400es(struct mmc_card *card)
>                 goto out_err;
>
>         err = mmc_select_bus_width(card);
> -       if (err < 0)
> +       if (err != MMC_BUS_WIDTH_8) {
> +               pr_err("%s: switch to 8bit bus width failed, err:%d\n",
> +                       mmc_hostname(host), err);
> +               err = -EIO;
>                 goto out_err;

ENOTSUPP seems more like the correct one.

Something like this:

err = err < 0 ? err : -ENOTSUPP;


> +       }
>
>         /* Switch card to HS mode */
>         err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> --
> 1.9.1
>

Kind regards
Uffe