Subject: [PATCH v2] mmc: core: Fix init_card in 52Mhz

From: [email-masked] (Adrian Hunter)
Date: Thu, 8 Oct 2015 16:03:04 +0300

On 08/10/15 13:59, Ulf Hansson wrote:
> On 8 October 2015 at 09:09, Chaotian Jing <[email-masked]> wrote:
>> Suppose that we got a data crc error, and it triggers the mmc_reset.
>> mmc_reset will call mmc_send_status to see if HW reset was supported.
>> before issue CMD13, it will do retune, and if EMMC was in HS400 mode,
>> it will reduce frequency to 52Mhz firstly, then results in card init
>> was doing at 52Mhz.
>> The mmc_send_status was originally only done for mmc_test, so if retune
>> needed, do not call mmc_send_status.
>>
>> Signed-off-by: Chaotian Jing <[email-masked]>
>> Suggested-by: Adrian Hunter <[email-masked]>
>> ---
>>  drivers/mmc/card/mmc_test.c | 6 ++++++
>>  drivers/mmc/core/mmc.c      | 2 +-
>>  2 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/card/mmc_test.c b/drivers/mmc/card/mmc_test.c
>> index b78cf5d..2f78bfb 100644
>> --- a/drivers/mmc/card/mmc_test.c
>> +++ b/drivers/mmc/card/mmc_test.c
>> @@ -2272,6 +2272,12 @@ static int mmc_test_hw_reset(struct mmc_test_card *test)
>>         if (!mmc_card_mmc(card) || !mmc_can_reset(card))
>>                 return RESULT_UNSUP_CARD;
>>
>> +       if (host->need_retune) {
>> +               pr_info("%s: cannot test hw reset because retune needed\n",
>> +                       mmc_hostname(test->card->host));
>> +               return RESULT_FAIL;
>> +       }
>> +
>>         err = mmc_hw_reset(host);
>>         if (!err)
>>                 return RESULT_OK;
>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>> index e726903..647c96d 100644
>> --- a/drivers/mmc/core/mmc.c
>> +++ b/drivers/mmc/core/mmc.c
>> @@ -1938,7 +1938,7 @@ static int mmc_reset(struct mmc_host *host)
>>         host->ops->hw_reset(host);
>>
>>         /* If the reset has happened, then a status command will fail */
>> -       if (!mmc_send_status(card, &status)) {
>> +       if (!host->need_retune && !mmc_send_status(card, &status)) {
> 
> No, this seem like the wrong solution! The main purpose of mmc_reset()
> is to try to reset and re-initiate the card, to make it operational
> again.
> 
> I can't find a good reason to why we want to do a mmc_send_status() at
> this point, as even if it succeeds it will only tell us that the card
> has not been "hw-reset". No matter what, we should still try to make
> it fully operational again and thus give mmc_init_card() a try.
> 
>>>From this reasoning, I suggest we remove the call to mmc_send_status()
> from this path, as that will also address your issue with CRC errors
> in combination with re-tune.

Then you need to remove the hw_reset test from mmc_test.  Refer:

	http://marc.info/?l=linux-mmc&m=144360165906544&w=2