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 15:42:42 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	Seungwon Jeon <tgih.jun@...sung.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

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 ?
>
> Best regards,
> Seungwon Jeon.
>
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