linux-kernel - Re: [PATCH] mmc: block: disable the reliable write If the card does not support CMD23

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Date:	Thu, 27 Aug 2015 15:22:44 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Yong Li <sdliyong@...il.com>
Cc:	Chris Ball <chris@...ntf.net>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: block: disable the reliable write If the card does
 not support CMD23

On 25 August 2015 at 14:06, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> On 14 August 2015 at 09:30,  <sdliyong@...il.com> wrote:
>> From: Yong Li <sdliyong@...il.com>
>>
>> Signed-off-by: Yong Li <sdliyong@...il.com>
>> ---
>>  drivers/mmc/card/block.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>> index 452782b..d9e3c45 100644
>> --- a/drivers/mmc/card/block.c
>> +++ b/drivers/mmc/card/block.c
>> @@ -1366,7 +1366,8 @@ static void mmc_blk_rw_rq_prep(struct mmc_queue_req *mqrq,
>>         bool do_rel_wr = ((req->cmd_flags & REQ_FUA) ||
>>                           (req->cmd_flags & REQ_META)) &&
>>                 (rq_data_dir(req) == WRITE) &&
>> -               (md->flags & MMC_BLK_REL_WR);
>> +               (md->flags & MMC_BLK_REL_WR) &&
>> +               !(card->quirks & MMC_QUIRK_BLK_NO_CMD23);
>
> Further down in mmc_blk_rw_rq_prep() we check for
> MMC_QUIRK_BLK_NO_CMD23. That check becomes redundant after this
> change, please remove that check as a part of this patch as well.
>
>>
>>         memset(brq, 0, sizeof(struct mmc_blk_request));
>>         brq->mrq.cmd = &brq->cmd;
>> --
>> 2.1.0
>>
>

Please ignore my previous answer. MMC_QUIRK_BLK_NO_CMD23 is intended
to indicate to the mmc block layer whether using CMD23 for regular
block IO request could have a performance impact for some cards. If
that's the case we don't use it - except when using reliable write!

So this patch is just plain wrong.

Kind regards
Uffe
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