linux-kernel - Re: [PATCH v2] mmc: core: Verify SD bus width

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Message-ID: <CAPDyKFpGC2siKvv3dAJWQUJw7O5ajX1PG4BO51xz+F55yJvN8w@mail.gmail.com>
Date:   Mon, 29 Apr 2019 12:00:43 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Raul Rangel <rrangel@...omium.org>
Cc:     Avri Altman <Avri.Altman@....com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "djkurtz@...omium.org" <djkurtz@...omium.org>,
        "zwisler@...omium.org" <zwisler@...omium.org>,
        hongjiefang <hongjiefang@...micro.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Kyle Roeschley <kyle.roeschley@...com>
Subject: Re: [PATCH v2] mmc: core: Verify SD bus width

On Wed, 24 Apr 2019 at 17:57, Raul Rangel <rrangel@...omium.org> wrote:
>
> On Thu, Apr 18, 2019 at 06:20:26AM +0000, Avri Altman wrote:
> > >
> > > The SD Physical Layer Spec says the following: Since the SD Memory Card
> > > shall support at least the two bus modes 1-bit or 4-bit width, then any SD
> > > Card shall set at least bits 0 and 2 (SD_BUS_WIDTH="0101").
> > >
> > > This change verifies the card has specified a bus width.
> > >
> > > AMD SDHC Device 7806 can get into a bad state after a card disconnect
> > > where anything transferred via the DATA lines will always result in a
> > > zero filled buffer. Currently the driver will continue without error if
> > > the HC is in this condition. A block device will be created, but reading
> > > from it will result in a zero buffer. This makes it seem like the SD
> > > device has been erased, when in actuality the data is never getting
> > > copied from the DATA lines to the data buffer.
> > >
> > > SCR is the first command in the SD initialization sequence that uses the
> > > DATA lines. By checking that the response was invalid, we can abort
> > > mounting the card.
> > >
> > > Acked-by: Avri Altman <avri.altman@....com>
> > >
> > > Signed-off-by: Raul E Rangel <rrangel@...omium.org>
> > Reviewed-by: Avri Altman <avri.altman@....com>
> >
> > Thanks,
> > Avri
> Thanks for the review. Should I rebase this on master so it applies
> cleanly without the MMC trace patches?

Yes, please do!

Kind regards
Uffe