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Date:   Fri, 16 Oct 2020 14:50:54 +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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References: <20201015231149.9333-1-michael@walle.cc>
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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.

-michael