Re: [PATCH] mmc: core: Fix init_card in 52Mhz

Adrian Hunter
2015-09-30T13:04:51Z

On 30/09/15 12:03, Chaotian Jing wrote:
> On Wed, 2015-09-30 at 11:24 +0300, Adrian Hunter wrote:
>> On 30/09/15 06:28, Chaotian Jing 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, that results in card init
>>> was doing at 52Mhz, So need ensure frequency is lower than 400Khz when
>>> re-init card.
>>
>> The call to mmc_send_status() was originally only done for mmc_test and
>> doesn't belong in a real reset. However the test parameter was removed
>> to simplify the code by:
>>
>> commit 83533ab28380f6957af39a7b322e639e42dbdaf1
>> Author: Johan Rudholm <johan.rudholm@axis.com>
>> Date: Mon Jan 12 15:38:04 2015 +0100
>>
>> mmc: core: always check status after reset
>>
>> Always check if the card is alive after a successful reset. This allows
>> us to remove mmc_hw_reset_check(), leaving mmc_hw_reset() as the only
>> card reset interface.
>>
>> Signed-off-by: Johan Rudholm <johanru@axis.com>
>> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>>
>> IMHO having a test to check whether hw reset actually did reset the card
>> is useful, so I would suggest putting back mmc_hw_reset_check() and
>> removing the check from the non-test path.
>>
>> An alternative is to recognize that we don't want retuning here, and it is
>> unlikely to be needed in the mmc_test case. So if retuning is needed, just
>> skip the call to mmc_send_status() i.e.
>>
>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>> index f2d0c2ae85b1..c3749ba42739 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)) {
>> mmc_host_clk_release(host);
>> return -ENOSYS;
>> }
>>
>> Could then make mmc_test aware of that:
>>
>
>> This solution is better, please help to upstream it. Thx!

Then please, make it a patch, and test it and submit it. You can add:

Suggested-by: Adrian Hunter <adrian.hunter@intel.com>

>> diff --git a/drivers/mmc/card/mmc_test.c b/drivers/mmc/card/mmc_test.c
>> index b78cf5d403a3..7b105b97be78 100644
>> --- a/drivers/mmc/card/mmc_test.c
>> +++ b/drivers/mmc/card/mmc_test.c
>> @@ -2272,6 +2272,16 @@ static int mmc_test_hw_reset(struct mmc_test_card *test)
>> if (!mmc_card_mmc(card) || !mmc_can_reset(card))
>> return RESULT_UNSUP_CARD;
>>
>> + err = mmc_send_status(card, NULL);
>> + if (err)
>> + return err;
>> +
>> + 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 f2d0c2ae85b1..c3749ba42739 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)) {
>> mmc_host_clk_release(host);
>> return -ENOSYS;
>> }
>>
>>
>>
>>
>>>
>>> Signed-off-by: Chaotian Jing <chaotian.jing@mediatek.com>
>>> ---
>>> drivers/mmc/core/mmc.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>>> index e726903..f2d0c2a 100644
>>> --- a/drivers/mmc/core/mmc.c
>>> +++ b/drivers/mmc/core/mmc.c
>>> @@ -1945,6 +1945,7 @@ static int mmc_reset(struct mmc_host *host)
>>>
>>> /* Set initial state and call mmc_set_ios */
>>> mmc_set_initial_state(host);
>>> + mmc_set_clock(host, host->f_init);
>>> mmc_host_clk_release(host);
>>>
>>> return mmc_init_card(host, card->ocr, card);
>>>
>>
>
>
>