linux-kernel - RE: [PATCH V2] mmc: core: improve reasonableness of bus width setting for HS400es

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Date:   Mon, 16 Jul 2018 11:01:33 +0000
From:   Fang Hongjie(方洪杰) 
        <hongjiefang@...micro.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
CC:     Adrian Hunter <adrian.hunter@...el.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "Wolfram Sang" <wsa+renesas@...g-engineering.com>,
        Bastian Stender <bst@...gutronix.de>,
        Jin Qian <jinqian@...gle.com>, 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 V2] mmc: core: improve reasonableness of bus width
 setting for HS400es

> On 11 July 2018 at 05:00, 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 | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> > index 4466f5d..4bd6c09 100644
> > --- a/drivers/mmc/core/mmc.c
> > +++ b/drivers/mmc/core/mmc.c
> > @@ -1021,8 +1021,11 @@ static int mmc_select_bus_width(struct mmc_card *card)
> >                                  EXT_CSD_BUS_WIDTH,
> >                                  ext_csd_bits[idx],
> >                                  card->ext_csd.generic_cmd6_time);
> > -               if (err)
> > +               if (err) {
> > +                       if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_HS400ES)
> > +                               return err;
> >                         continue;
> > +               }
> 
> I would rather let mmc_select_hs400es() check the return code from
> mmc_select_bus_width().
> 
> So, if the return code isn't MMC_BUS_WIDTH_8, mmc_select_hs400es()
> should bail out.

Yeah, it is better that let mmc_select_hs400es() check the return value.
I will update the patch.

> 
> [...]
> 
> Kind regards
> Uffe


B&R
Hongjie