? 2016/7/19 18:31, Ulf Hansson ??:
> On 19 July 2016 at 10:58, Shawn Lin <shawn.lin at rock-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 at rock-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
