linux-kernel - RE: [PATCH v4 2/2] mmc: core: Support packed command for eMMC4.5 device

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Message-id: <004301ccec3f$4a4e9320$deebb960$%jun@samsung.com>
Date:	Thu, 16 Feb 2012 09:09:45 +0900
From:	Seungwon Jeon <tgih.jun@...sung.com>
To:	merez@...eaurora.org
Cc:	linux-mmc@...r.kernel.org, 'Chris Ball' <cjb@...top.org>,
	linux-kernel@...r.kernel.org
Subject: RE: [PATCH v4 2/2] mmc: core: Support packed command for eMMC4.5 device

Maya Erez <merez@...eaurora.org> wrote:
> > @@ -1065,12 +1075,60 @@ static int mmc_blk_err_check(struct mmc_card
> > *card,
> >  	if (!brq->data.bytes_xfered)
> >  		return MMC_BLK_RETRY;
> >
> > +	if (mq_mrq->packed_cmd != MMC_PACKED_NONE) {
> > +		if (unlikely(brq->data.blocks << 9 != brq->data.bytes_xfered))
> > +			return MMC_BLK_PARTIAL;
> > +		else
> > +			return MMC_BLK_SUCCESS;
> > +	}
> > +
> >  	if (blk_rq_bytes(req) != brq->data.bytes_xfered)
> >  		return MMC_BLK_PARTIAL;
> >
> >  	return MMC_BLK_SUCCESS;
> >  }
> I think it would be best to keep the request length (brq->data.blocks << 9
> or blk_rq_bytes(req)) in a variable and use it in the original if above.
> This way you can avoid doubling the exit points from the function.
In case of packed command, brq->data.blocks contains the sum of blocks for individual request.
That means blk_rq_bytes(req) doesn't represent all packed length bytes.
And "brq->data.blocks << 9" is not idential to blk_rq_bytes(req) in non-packed command.
"brq->data.blocks" is overwritten during request preparation by the following reasons.
- brq->data.blocks > card->host->max_blk_count
- disable_multi
- do_rel_wr
So "brq->data.blocks << 9" is not good choice for request length  in non-packed command.

Thanks,
Seungwon Jeon

> Thanks,
> Maya Erez
> Consultant for Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum
> 
> 
> 
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