linux-kernel - RE: [PATCH v3 2/2] mmc: core: Support packed command for eMMC4.5 device

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Date:	Thu, 26 Jan 2012 16:24:42 +0900
From:	Seungwon Jeon <tgih.jun@...sung.com>
To:	'Namjae Jeon' <linkinjeon@...il.com>
Cc:	'Saugata Das' <saugata.das@...aro.org>, linux-mmc@...r.kernel.org,
	'Chris Ball' <cjb@...top.org>, linux-kernel@...r.kernel.org
Subject: RE: [PATCH v3 2/2] mmc: core: Support packed command for eMMC4.5 device

Namjae Jeon <linkinjeon@...il.com>:
> 2012/1/26 Seungwon Jeon <tgih.jun@...sung.com>:
> > Namjae Jeon <linkinjeon@...il.com>:
> >> 2012/1/25 Namjae Jeon <linkinjeon@...il.com>:
> >> >>> >> +
> >> >>> >> +static int mmc_blk_issue_packed_rd(struct mmc_queue *mq,
> >> >>> >> +               struct mmc_queue_req *mq_rq)
> >> >>> >> +{
> >> >>> >> +       struct mmc_blk_data *md = mq->data;
> >> >>> >> +       struct mmc_card *card = md->queue.card;
> >> >>> >> +       int status, ret = -EIO, retry = 2;
> >> > Hi. Seungwon.
> >> > First Thansk for your reply.
> >> > There is one more my review comment.
> >> > I think that EIO of ret is not needed. there is no case to be skipped
> >> > if/ese condition in do while loop.
> > Oh, no need practically.
> > Thank you for your inspection.
> >
> >>
> >> Hi. Seungwon.
> >>
> >>   if ((!mmc_host_is_spi(card->host) && rq_data_dir(req) != READ) ||
> >> +                       (mq_mrq->packed_cmd == MMC_PACKED_WR_HDR)) {
> >>
> >> it seems more better that upper if condition is changed like the below.
> > Do you have any reason for your comment?
> > Packed command(4.5 feature) is regardless of SPI.
> > SPI mode has been removed since version 4.3.
> >
> >>
> >> if (!mmc_host_is_spi(card->host) && ((rq_data_dir(req) != READ) ||
> >> +                       (mq_mrq->packed_cmd == MMC_PACKED_WR_HDR))) {
> >>
> >>
> >> +++ b/drivers/mmc/core/host.c
> >> @@ -346,6 +346,8 @@ struct mmc_host *mmc_alloc_host(int extra, struct
> >> device *dev)
> >>        host->max_blk_size = 512;
> >>        host->max_blk_count = PAGE_CACHE_SIZE / 512;
> >>
> >> +       host->packed_min = 2;
> >> +
> >>        return host;
> >>
> >> if packed_min is fixed value without increasing/decreasing,  it seems
> >> more better to use macro.
> >> Thanks.
> > packed_min is not fixed value.
> > Could you refer the following is changes log about v3?
> >
> > Changes in v3:
> >        - Add a variable member in mmc_host for minimum number of packed entries.
> >          This value can be overridden by host.
> Ah.. Okay~ I clearly understand about two queston.
> Totally, Looks good to me.
> Thanks for your reply.
> And I heard that packed cmd is not good while reading small chunk,
> If so, I want to use packed write cmd not read cmd.
> Can I use packed only packed write cmd by seperating
> MMC_CAP2_PACKED_READ_CMD and MMC_CAP2_PACKED_WRITE_CMD ?
Do you think this separate use is common?
Let me consider this more.

> >
> > Best regards,
> > Seungwon Jeon.
> >
> >> --
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