linux-kernel - Re: [PATCH] mmc: sdhci-of-esdhc: set timeout to max before tuning

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Date:   Wed, 21 Oct 2020 17:04:17 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Michael Walle <michael@...le.cc>
Cc:     "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Yangbo Lu <yangbo.lu@....com>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH] mmc: sdhci-of-esdhc: set timeout to max before tuning

On Fri, 16 Oct 2020 at 14:50, Michael Walle <michael@...le.cc> wrote:
>
> Am 2020-10-16 12:53, schrieb Ulf Hansson:
> > On Fri, 16 Oct 2020 at 01:12, Michael Walle <michael@...le.cc> wrote:
> >>
> >> On rare occations there is the following error:
> >>
> >>   mmc0: Tuning timeout, falling back to fixed sampling clock
> >>
> >> There are SD cards which takes a significant longer time to reply to
> >> the
> >> first CMD19 command. The eSDHC takes the data timeout value into
> >> account
> >> during the tuning period. The SDHCI core doesn't explicitly set this
> >> timeout for the tuning procedure. Thus on the slow cards, there might
> >> be
> >> a spurious "Buffer Read Ready" interrupt, which in turn triggers a
> >> wrong
> >> sequence of events. In the end this will lead to an unsuccessful
> >> tuning
> >> procedure and to the above error.
> >>
> >> To workaround this, set the timeout to the maximum value (which is the
> >> best we can do) and the SDHCI core will take care of the proper
> >> timeout
> >> handling.
> >>
> >> Signed-off-by: Michael Walle <michael@...le.cc>
> >
> > Sound like this should be tagged for stable, right?
>
> Yes, but I was unsure about that. I didn't find a lot of Fixes: tags in
> the history of this driver (eg. for errata etc.)
>
> I could repost a v2 with a fixes tag if you like.

If this is regression and you can point to a specific commit it fixes,
then please yes!

Kind regards
Uffe