linux-kernel - Re: [PATCH 2/2] mmc: core: fall back host->f_init if failing to init mmc card after resume

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Date:	Wed, 20 Jul 2016 09:33:10 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	shawn.lin@...k-chips.com, Adrian Hunter <adrian.hunter@...el.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Doug Anderson <dianders@...omium.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH 2/2] mmc: core: fall back host->f_init if failing to init
 mmc card after resume

在 2016/7/19 18:31, Ulf Hansson 写道:
> On 19 July 2016 at 10:58, Shawn Lin <shawn.lin@...k-chips.com> wrote:
>> We observed the failure of initializing card after resume
>> accidentally. It's hard to reproduce but we did get report from
>> the suspend/resume test of our RK3399 mp test farm . Unfortunately,
>> we still fail to figure out what was going wrong at that time.
>> Also we can't achieve it by retrying the host->f_init without falling
>> back it. But this patch will solve the problem as we could add some log
>> there and see that we resume the mmc card successfully after falling
>> back the host->f_init. There is no obvious side effect found, so it seems
>> this patch will improve the stability.
>
> What f_init did the original rescan work find out being successful?

The original f_init was 400k when booting up the system.

>
> Did you then verify that it was *another* frequency that made the
> initialization to work in the resume?

yes, I added some log and saw 100k made the initialization to work in
the resume finally with the patch applied.

Also I mentioned in the commit msg that if I just retried 400K, it
cannot made the initialization successful.

>
>>
>> [   93.405085] mmc1: unexpected status 0x800900 after switch
>> [   93.408474] mmc1: switch to bus width 1 failed
>> [   93.408482] mmc1: mmc_select_hs200 failed, error -110
>> [   93.408492] mmc1: error -110 during resume (card was removed?)
>> [   93.408705] PM: resume of devices complete after 213.453 msecs
>>
>> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
>> ---
>>
>>  drivers/mmc/core/mmc.c | 22 ++++++++++++++++++++--
>>  1 file changed, 20 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>> index 403b97b..bef40c8 100644
>> --- a/drivers/mmc/core/mmc.c
>> +++ b/drivers/mmc/core/mmc.c
>> @@ -1945,6 +1945,7 @@ static int mmc_suspend(struct mmc_host *host)
>>  static int _mmc_resume(struct mmc_host *host)
>>  {
>>         int err = 0;
>> +       int i;
>>
>>         BUG_ON(!host);
>>         BUG_ON(!host->card);
>> @@ -1954,8 +1955,25 @@ static int _mmc_resume(struct mmc_host *host)
>>         if (!mmc_card_suspended(host->card))
>>                 goto out;
>>
>> -       mmc_power_up(host, host->card->ocr);
>> -       err = mmc_init_card(host, host->card->ocr, host->card);
>> +       /*
>> +        * Let's try to fallback the host->f_init
>> +        * if failing to init card after resume.
>> +        */
>> +
>> +       for (i = 0; i < ARRAY_SIZE(freqs); i++) {
>> +               if (host->f_init < freqs[i])
>> +                       continue;
>> +               else
>> +                       host->f_init = freqs[i];
>
> This loop is wrong, as you don't consider that host->f_min may not
> exactly match the frequencies in the freqs array.

Ah, seems I should use 'max(freqs[i], host->f_min)'.. :)

>
>> +
>> +               mmc_power_up(host, host->card->ocr);
>> +               err = mmc_init_card(host, host->card->ocr, host->card);
>> +               if (!err)
>> +                       break;
>> +
>> +               mmc_power_off(host);
>
> The mmc core expects the host/card to be powered up after a resume, as
> it may send commands to it without first invoking mmc_power_up().
> Even if those commands may fail (or timeout), at least those doesn't
> hang which may be the case if the host/card isn't powered up first.
>

I got it, thanks.

> So, you must *not* leave the host/card in "mmc_power_off()" state in
> _mmc_resume().
>
> [...]
>
> Kind regards
> Uffe
>
>
>


-- 
Best Regards
Shawn Lin