linux-kernel - Re: [PATCH] mmc: core: Fix init

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Date:	Wed, 30 Sep 2015 16:01:11 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Chaotian Jing <chaotian.jing@...iatek.com>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Johan Rudholm <johan.rudholm@...s.com>,
	Gwendal Grignou <gwendal@...omium.org>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
	Sascha Hauer <kernel@...gutronix.de>
Subject: Re: [PATCH] mmc: core: Fix init_card in 52Mhz

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@...s.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@...s.com>
>>     Signed-off-by: Ulf Hansson <ulf.hansson@...aro.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@...el.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@...iatek.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);
>>>
>>
> 
> 
> 

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