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Date:   Wed, 21 Oct 2020 19:29:47 +0200
From:   Michael Walle <michael@walle.cc>
To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     linux-mmc@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Yangbo Lu <yangbo.lu@nxp.com>,
        Adrian Hunter <adrian.hunter@intel.com>
Subject: Re: [PATCH] mmc: sdhci-of-esdhc: set timeout to max before tuning
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Am 2020-10-21 17:04, schrieb Ulf Hansson:
> On Fri, 16 Oct 2020 at 14:50, Michael Walle <michael@walle.cc> wrote:
>> 
>> Am 2020-10-16 12:53, schrieb Ulf Hansson:
>> > On Fri, 16 Oct 2020 at 01:12, Michael Walle <michael@walle.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@walle.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!

That would be commit ba49cbd0936e ("mmc: sdhci-of-esdhc: add tuning
support"). But as of today it isn't much left of that original code.
So I don't know if adding that fixes tag will help a lot. Correct me
if I'm wrong.

-michael