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

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Date:	Wed, 30 Sep 2015 17:03:01 +0800
From:	Chaotian Jing <chaotian.jing@...iatek.com>
To:	Adrian Hunter <adrian.hunter@...el.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 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!
> 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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