On Fri, May 20, 2011 at 5:29 AM, Jaehoon Chung <jh80.chung@xxxxxxxxxxx> wrote:
> Hi Andrei.
>
> I have some question..
> In mmc_blk_issue_rw_rq() of block.c, there is the below code.
>
> static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *req)
> {
> struct mmc_blk_data *md = mq->data;
> struct mmc_card *card = md->queue.card;
> struct mmc_blk_request brq;
> int ret = 1, disable_multi = 0;
>
> /*
> * Reliable writes are used to implement Forced Unit Access and
> * REQ_META accesses, and are supported only on MMCs.
> */
> bool do_rel_wr = ((req->cmd_flags & REQ_FUA) ||
> (req->cmd_flags & REQ_META)) &&
> (rq_data_dir(req) == WRITE) &&
> REL_WRITES_SUPPORTED(card);
>
> do {
> struct mmc_command cmd = {0};
> u32 readcmd, writecmd, status = 0;
>
> memset(&brq, 0, sizeof(struct mmc_blk_request));
> brq.mrq.cmd = &brq.cmd;
> brq.mrq.data = &brq.data;
>
> brq.cmd.arg = blk_rq_pos(req);
> if (!mmc_card_blockaddr(card))
> brq.cmd.arg <<= 9;
> brq.cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC;
> brq.data.blksz = 512;
> brq.stop.opcode = MMC_STOP_TRANSMISSION;
> brq.stop.arg = 0;
> brq.stop.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
> brq.data.blocks = blk_rq_sectors(req);
>
> There is "brq.stop.opcode = MMC_STOP_TRANSMISSION".
> If we use CMD23, this line didn't need? Actually i don't know, so i ask to you.
>
Nope. Needed. CMD23 support might not be implemented by host driver
(like it isn't right now for anything non-SDHCI). And even it if were,
you still need to send stop command on any error conditions. I suggest
you read the relevant sections in the publically available eMMC spec.
A
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