linux-kernel - Re: [PATCH] mmc: core: fix dead loop of mmc

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Message-ID: <CAPDyKFrVWGP2nXZR63v0r7eRKmHuKdX1=FMjGRhOaNtDaKTg8Q@mail.gmail.com>
Date:	Wed, 30 Sep 2015 14:47:39 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Chaotian Jing <chaotian.jing@...iatek.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Johan Rudholm <johan.rudholm@...s.com>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Shawn Lin <shawn.lin@...k-chips.com>,
	Andrew Gabbasov <andrew_gabbasov@...tor.com>,
	David Jander <david@...tonic.nl>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-mediatek@...ts.infradead.org,
	srv_heupstream <srv_heupstream@...iatek.com>,
	Sascha Hauer <kernel@...gutronix.de>
Subject: Re: [PATCH] mmc: core: fix dead loop of mmc_retune

On 30 September 2015 at 14:01, Adrian Hunter <adrian.hunter@...el.com> wrote:
> On 30/09/15 12:37, Chaotian Jing wrote:
>> When get a CRC error, start the mmc_retune, it will issue CMD19/CMD21
>> to do tune, assume there were 10 clock phase need to try, phase 0 to
>> phase 6 is ok, phase 7 to phase 9 is NG, we try it from 0 to 9, so
>> the last CMD19/CMD21 will get CRC error, host->need_retune was set and
>> cause mmc_retune was called, then dead loop of mmc_retune
>>
>> Signed-off-by: Chaotian Jing <chaotian.jing@...iatek.com>
>
> Wasn't my idea to have this CRC checking in the core ;-) and sdhci
> doesn't put it's tuning commands through a mmc request so it doesn't
> see this issue.

That's not true for all sdhci variants. For those that uses sdhci's
->platform_execute_tuning() callback, all uses mmc_send_tuning().

I think for sdhci's default tuning path, we should change to use
mmc_send_tuning() and thus we would potentially hit this problem as
well.

>
> But definitely the CRC logic is not meant for the tuning commands, so
>
> Acked-by: Adrian Hunter <adrian.hunter@...el.com>

Thanks for reviewing Adrian and for keeping an eye on "tuning" related patches.

Kind regards
Uffe
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