mmc驅動框架分析2

mmc驅動框架分析1中，分析了sd卡的初始化流程，本文主要分析sd卡的讀寫過程。先貼一張圖，網上網友畫的，非常清晰，表示感謝。

從mmc驅動框架分析1中，可以看到mmcblock設備的請求處理函數爲mmc_request，先從這個函數分析

static void mmc_request(struct request_queue *q)
{
	struct mmc_queue *mq = q->queuedata;
	struct request *req;

	if (!mq) {
		while ((req = blk_fetch_request(q)) != NULL) {
			req->cmd_flags |= REQ_QUIET;
			__blk_end_request_all(req, -EIO);
		}
		return;
	}

	if (!mq->mqrq_cur->req && !mq->mqrq_prev->req)
		wake_up_process(mq->thread);
}

static int mmc_queue_thread(void *d)
{
	struct mmc_queue *mq = d;
	struct request_queue *q = mq->queue;

	current->flags |= PF_MEMALLOC;

	down(&mq->thread_sem);
	do {
		struct request *req = NULL;
		struct mmc_queue_req *tmp;

		spin_lock_irq(q->queue_lock);
		set_current_state(TASK_INTERRUPTIBLE);
		req = blk_fetch_request(q);	//取出一個請求
		mq->mqrq_cur->req = req;
		spin_unlock_irq(q->queue_lock);

		if (req || mq->mqrq_prev->req) {
			set_current_state(TASK_RUNNING);
			mq->issue_fn(mq, req);	//調用issue_fn接口函數，對應mmc_blk_issue_rq
		} else {
			if (kthread_should_stop()) {
				set_current_state(TASK_RUNNING);
				break;
			}
			up(&mq->thread_sem);
			schedule();
			down(&mq->thread_sem);
		}

		/* Current request becomes previous request and vice versa. */
		mq->mqrq_prev->brq.mrq.data = NULL;
		mq->mqrq_prev->req = NULL;
		tmp = mq->mqrq_prev;
		mq->mqrq_prev = mq->mqrq_cur;
		mq->mqrq_cur = tmp;
	} while (1);
	up(&mq->thread_sem);

	return 0;
}

static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
{
	int ret;
	struct mmc_blk_data *md = mq->data;
	struct mmc_card *card = md->queue.card;

	if (req && !mq->mqrq_prev->req)
		/* claim host only for the first request */
		mmc_claim_host(card->host);

	ret = mmc_blk_part_switch(card, md);
	if (ret) {
		ret = 0;
		goto out;
	}

	if (req && req->cmd_flags & REQ_DISCARD) {
		/* complete ongoing async transfer before issuing discard */
		if (card->host->areq)
			mmc_blk_issue_rw_rq(mq, NULL);
		if (req->cmd_flags & REQ_SECURE)
			ret = mmc_blk_issue_secdiscard_rq(mq, req);
		else
			ret = mmc_blk_issue_discard_rq(mq, req);
	} else if (req && req->cmd_flags & REQ_FLUSH) {
		/* complete ongoing async transfer before issuing flush */
		if (card->host->areq)
			mmc_blk_issue_rw_rq(mq, NULL);
		ret = mmc_blk_issue_flush(mq, req);
	} else {
		ret = mmc_blk_issue_rw_rq(mq, req);	//對於普通的讀寫，調用這個函數
	}

out:
	if (!req)
		/* release host only when there are no more requests */
		mmc_release_host(card->host);
	return ret;
}

static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
{
	struct mmc_blk_data *md = mq->data;
	struct mmc_card *card = md->queue.card;
	struct mmc_blk_request *brq = &mq->mqrq_cur->brq;
	int ret = 1, disable_multi = 0, retry = 0;
	enum mmc_blk_status status;
	struct mmc_queue_req *mq_rq;
	struct request *req;
	struct mmc_async_req *areq;

	if (!rqc && !mq->mqrq_prev->req)
		return 0;

	do {
		if (rqc) {
			mmc_blk_rw_rq_prep(mq->mqrq_cur, card, 0, mq);
			areq = &mq->mqrq_cur->mmc_active;	//取得異步request結構體
		} else
			areq = NULL;
		areq = mmc_start_req(card->host, areq, (int *) &status);	//正式開始請求
		if (!areq)
			return 0;

		mq_rq = container_of(areq, struct mmc_queue_req, mmc_active);
		brq = &mq_rq->brq;
		req = mq_rq->req;
		mmc_queue_bounce_post(mq_rq);

		switch (status) {	//對完成狀態進行判斷
		case MMC_BLK_SUCCESS:
		case MMC_BLK_PARTIAL:
			/*
			 * A block was successfully transferred.
			 */
			spin_lock_irq(&md->lock);
			ret = __blk_end_request(req, 0,
						brq->data.bytes_xfered);
			spin_unlock_irq(&md->lock);
			if (status == MMC_BLK_SUCCESS && ret) {
				/*
				 * The blk_end_request has returned non zero
				 * even though all data is transfered and no
				 * erros returned by host.
				 * If this happen it's a bug.
				 */
				printk(KERN_ERR "%s BUG rq_tot %d d_xfer %d\n",
				       __func__, blk_rq_bytes(req),
				       brq->data.bytes_xfered);
				rqc = NULL;
				goto cmd_abort;
			}
			break;
		case MMC_BLK_CMD_ERR:
			goto cmd_err;
		case MMC_BLK_RETRY_SINGLE:
			disable_multi = 1;
			break;
		case MMC_BLK_RETRY:
			if (retry++ < 5)
				break;
		case MMC_BLK_ABORT:
			goto cmd_abort;
		case MMC_BLK_DATA_ERR:
			/*
			 * After an error, we redo I/O one sector at a
			 * time, so we only reach here after trying to
			 * read a single sector.
			 */
			spin_lock_irq(&md->lock);
			ret = __blk_end_request(req, -EIO,
						brq->data.blksz);
			spin_unlock_irq(&md->lock);
			if (!ret)
				goto start_new_req;
			break;
		}

		if (ret) {
			/*
			 * In case of a none complete request
			 * prepare it again and resend.
			 */
			mmc_blk_rw_rq_prep(mq_rq, card, disable_multi, mq);
			mmc_start_req(card->host, &mq_rq->mmc_active, NULL);
		}
	} while (ret);

	return 1;

 cmd_err:
 	/*
 	 * If this is an SD card and we're writing, we can first
 	 * mark the known good sectors as ok.
 	 *
	 * If the card is not SD, we can still ok written sectors
	 * as reported by the controller (which might be less than
	 * the real number of written sectors, but never more).
	 */
	if (mmc_card_sd(card)) {
		u32 blocks;

		blocks = mmc_sd_num_wr_blocks(card);
		if (blocks != (u32)-1) {
			spin_lock_irq(&md->lock);
			ret = __blk_end_request(req, 0, blocks << 9);
			spin_unlock_irq(&md->lock);
		}
	} else {
		spin_lock_irq(&md->lock);
		ret = __blk_end_request(req, 0, brq->data.bytes_xfered);
		spin_unlock_irq(&md->lock);
	}

 cmd_abort:
	spin_lock_irq(&md->lock);
	while (ret)
		ret = __blk_end_request(req, -EIO, blk_rq_cur_bytes(req));
	spin_unlock_irq(&md->lock);

 start_new_req:
	if (rqc) {
		mmc_blk_rw_rq_prep(mq->mqrq_cur, card, 0, mq);
		mmc_start_req(card->host, &mq->mqrq_cur->mmc_active, NULL);
	}

	return 0;
}

struct mmc_async_req *mmc_start_req(struct mmc_host *host,
				    struct mmc_async_req *areq, int *error)
{
	int err = 0;
	struct mmc_async_req *data = host->areq;

	/* Prepare a new request */
	if (areq)
		mmc_pre_req(host, areq->mrq, !host->areq);
	//如果上次傳遞未完成，需要等待
	if (host->areq) {
		mmc_wait_for_req_done(host, host->areq->mrq);
		err = host->areq->err_check(host->card, host->areq);
		if (err) {
			mmc_post_req(host, host->areq->mrq, 0);
			if (areq)
				mmc_post_req(host, areq->mrq, -EINVAL);

			host->areq = NULL;
			goto out;
		}
	}

	if (areq)
		__mmc_start_req(host, areq->mrq);	//開始處理請求

	if (host->areq)
		mmc_post_req(host, host->areq->mrq, 0);

	host->areq = areq;
 out:
	if (error)
		*error = err;
	return data;
}

static void __mmc_start_req(struct mmc_host *host, struct mmc_request *mrq)
{
	init_completion(&mrq->completion);
	mrq->done = mmc_wait_done;
	mmc_start_request(host, mrq);
}

static void
mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
{
#ifdef CONFIG_MMC_DEBUG
	unsigned int i, sz;
	struct scatterlist *sg;
#endif

	pr_debug("%s: starting CMD%u arg %08x flags %08x\n",
		 mmc_hostname(host), mrq->cmd->opcode,
		 mrq->cmd->arg, mrq->cmd->flags);

	if (mrq->data) {
		pr_debug("%s:     blksz %d blocks %d flags %08x "
			"tsac %d ms nsac %d\n",
			mmc_hostname(host), mrq->data->blksz,
			mrq->data->blocks, mrq->data->flags,
			mrq->data->timeout_ns / 1000000,
			mrq->data->timeout_clks);
	}

	if (mrq->stop) {
		pr_debug("%s:     CMD%u arg %08x flags %08x\n",
			 mmc_hostname(host), mrq->stop->opcode,
			 mrq->stop->arg, mrq->stop->flags);
	}

	WARN_ON(!host->claimed);

	mrq->cmd->error = 0;
	mrq->cmd->mrq = mrq;
	if (mrq->data) {	//對於有數據傳輸要求的命令，要對data結構錯誤判斷
		BUG_ON(mrq->data->blksz > host->max_blk_size);
		BUG_ON(mrq->data->blocks > host->max_blk_count);
		BUG_ON(mrq->data->blocks * mrq->data->blksz >
			host->max_req_size);

#ifdef CONFIG_MMC_DEBUG
		sz = 0;
		for_each_sg(mrq->data->sg, sg, mrq->data->sg_len, i)
			sz += sg->length;
		BUG_ON(sz != mrq->data->blocks * mrq->data->blksz);
#endif

		mrq->cmd->data = mrq->data;
		mrq->data->error = 0;
		mrq->data->mrq = mrq;
		if (mrq->stop) {
			mrq->data->stop = mrq->stop;
			mrq->stop->error = 0;
			mrq->stop->mrq = mrq;
		}
	}
	mmc_host_clk_hold(host);
	led_trigger_event(host->led, LED_FULL);
	host->ops->request(host, mrq);	//調用host端的request函數，對應於s3cmci_request
}

上面是card層和core層對請求的處理，接下來看host層的處理：

static void s3cmci_request(struct mmc_host *mmc, struct mmc_request *mrq)
{
	struct s3cmci_host *host = mmc_priv(mmc);

	host->status = "mmc request";
	host->cmd_is_stop = 0;
	host->mrq = mrq;

	if (s3cmci_card_present(mmc) == 0) {
		dbg(host, dbg_err, "%s: no medium present\n", __func__);
		host->mrq->cmd->error = -ENOMEDIUM;
		mmc_request_done(mmc, mrq);
	} else
		s3cmci_send_request(mmc);
}

static void s3cmci_send_request(struct mmc_host *mmc)
{
	struct s3cmci_host *host = mmc_priv(mmc);
	struct mmc_request *mrq = host->mrq;
	struct mmc_command *cmd = host->cmd_is_stop ? mrq->stop : mrq->cmd;

	host->ccnt++;
	prepare_dbgmsg(host, cmd, host->cmd_is_stop);

	/* Clear command, data and fifo status registers
	   Fifo clear only necessary on 2440, but doesn't hurt on 2410
	*/
	writel(0xFFFFFFFF, host->base + S3C2410_SDICMDSTAT);
	writel(0xFFFFFFFF, host->base + S3C2410_SDIDSTA);
	writel(0xFFFFFFFF, host->base + S3C2410_SDIFSTA);

	if (cmd->data) {	//對於數據的處理
		int res = s3cmci_setup_data(host, cmd->data);

		host->dcnt++;

		if (res) {
			dbg(host, dbg_err, "setup data error %d\n", res);
			cmd->error = res;
			cmd->data->error = res;

			mmc_request_done(mmc, mrq);
			return;
		}

		if (s3cmci_host_usedma(host))	//使用DMA
			res = s3cmci_prepare_dma(host, cmd->data);
		else
			res = s3cmci_prepare_pio(host, cmd->data);	//不適用DMA

		if (res) {
			dbg(host, dbg_err, "data prepare error %d\n", res);
			cmd->error = res;
			cmd->data->error = res;

			mmc_request_done(mmc, mrq);
			return;
		}
	}

	/* Send command */
	s3cmci_send_command(host, cmd);	//對於命令的處理

	/* Enable Interrupt */
	s3cmci_enable_irq(host, true);
}

s3cmci_send_request函數分爲對數據和命令的處理，先看對命令的處理

static void s3cmci_send_command(struct s3cmci_host *host,
					struct mmc_command *cmd)
{
	u32 ccon, imsk;

	imsk  = S3C2410_SDIIMSK_CRCSTATUS | S3C2410_SDIIMSK_CMDTIMEOUT |
		S3C2410_SDIIMSK_RESPONSEND | S3C2410_SDIIMSK_CMDSENT |
		S3C2410_SDIIMSK_RESPONSECRC;

	enable_imask(host, imsk);

	if (cmd->data)
		host->complete_what = COMPLETION_XFERFINISH_RSPFIN;
	else if (cmd->flags & MMC_RSP_PRESENT)
		host->complete_what = COMPLETION_RSPFIN;
	else
		host->complete_what = COMPLETION_CMDSENT;	//任務標記

	writel(cmd->arg, host->base + S3C2410_SDICMDARG);

	ccon  = cmd->opcode & S3C2410_SDICMDCON_INDEX;
	ccon |= S3C2410_SDICMDCON_SENDERHOST | S3C2410_SDICMDCON_CMDSTART;

	if (cmd->flags & MMC_RSP_PRESENT)
		ccon |= S3C2410_SDICMDCON_WAITRSP;

	if (cmd->flags & MMC_RSP_136)
		ccon |= S3C2410_SDICMDCON_LONGRSP;

	writel(ccon, host->base + S3C2410_SDICMDCON);	//配置命令控制寄存器
}

static irqreturn_t s3cmci_irq(int irq, void *dev_id)
{
	struct s3cmci_host *host = dev_id;
	struct mmc_command *cmd;
	u32 mci_csta, mci_dsta, mci_fsta, mci_dcnt, mci_imsk;
	u32 mci_cclear = 0, mci_dclear;
	unsigned long iflags;

	mci_dsta = readl(host->base + S3C2410_SDIDSTA);
	mci_imsk = readl(host->base + host->sdiimsk);

	if (mci_dsta & S3C2410_SDIDSTA_SDIOIRQDETECT) {	//sdio相關
		if (mci_imsk & S3C2410_SDIIMSK_SDIOIRQ) {
			mci_dclear = S3C2410_SDIDSTA_SDIOIRQDETECT;
			writel(mci_dclear, host->base + S3C2410_SDIDSTA);

			mmc_signal_sdio_irq(host->mmc);
			return IRQ_HANDLED;
		}
	}

	spin_lock_irqsave(&host->complete_lock, iflags);

	mci_csta = readl(host->base + S3C2410_SDICMDSTAT);
	mci_dcnt = readl(host->base + S3C2410_SDIDCNT);
	mci_fsta = readl(host->base + S3C2410_SDIFSTA);
	mci_dclear = 0;

	if ((host->complete_what == COMPLETION_NONE) ||
	    (host->complete_what == COMPLETION_FINALIZE)) {
		host->status = "nothing to complete";
		clear_imask(host);
		goto irq_out;
	}

	if (!host->mrq) {
		host->status = "no active mrq";
		clear_imask(host);
		goto irq_out;
	}

	cmd = host->cmd_is_stop ? host->mrq->stop : host->mrq->cmd;

	if (!cmd) {
		host->status = "no active cmd";
		clear_imask(host);
		goto irq_out;
	}

	if (!s3cmci_host_usedma(host)) {
		if ((host->pio_active == XFER_WRITE) &&
		    (mci_fsta & S3C2410_SDIFSTA_TFDET)) {

			disable_imask(host, S3C2410_SDIIMSK_TXFIFOHALF);
			tasklet_schedule(&host->pio_tasklet);	//寫數據，激活tasklet
			host->status = "pio tx";
		}

		if ((host->pio_active == XFER_READ) &&
		    (mci_fsta & S3C2410_SDIFSTA_RFDET)) {

			disable_imask(host,
				      S3C2410_SDIIMSK_RXFIFOHALF |
				      S3C2410_SDIIMSK_RXFIFOLAST);

			tasklet_schedule(&host->pio_tasklet);	//讀數據，激活tasklet
			host->status = "pio rx";
		}
	}

	if (mci_csta & S3C2410_SDICMDSTAT_CMDTIMEOUT) {	//命令超時
		dbg(host, dbg_err, "CMDSTAT: error CMDTIMEOUT\n");
		cmd->error = -ETIMEDOUT;
		host->status = "error: command timeout";
		goto fail_transfer;
	}

	if (mci_csta & S3C2410_SDICMDSTAT_CMDSENT) {	//命令發出
		if (host->complete_what == COMPLETION_CMDSENT) {
			host->status = "ok: command sent";
			goto close_transfer;
		}

		mci_cclear |= S3C2410_SDICMDSTAT_CMDSENT;
	}

	if (mci_csta & S3C2410_SDICMDSTAT_CRCFAIL) {
		if (cmd->flags & MMC_RSP_CRC) {
			if (host->mrq->cmd->flags & MMC_RSP_136) {
				dbg(host, dbg_irq,
				    "fixup: ignore CRC fail with long rsp\n");
			} else {
				/* note, we used to fail the transfer
				 * here, but it seems that this is just
				 * the hardware getting it wrong.
				 *
				 * cmd->error = -EILSEQ;
				 * host->status = "error: bad command crc";
				 * goto fail_transfer;
				*/
			}
		}

		mci_cclear |= S3C2410_SDICMDSTAT_CRCFAIL;
	}

	if (mci_csta & S3C2410_SDICMDSTAT_RSPFIN) {	//收到響應
		if (host->complete_what == COMPLETION_RSPFIN) {
			host->status = "ok: command response received";
			goto close_transfer;
		}

		if (host->complete_what == COMPLETION_XFERFINISH_RSPFIN)
			host->complete_what = COMPLETION_XFERFINISH;

		mci_cclear |= S3C2410_SDICMDSTAT_RSPFIN;
	}

	/* errors handled after this point are only relevant
	   when a data transfer is in progress */

	if (!cmd->data)
		goto clear_status_bits;

	/* Check for FIFO failure */
	if (host->is2440) {
		if (mci_fsta & S3C2440_SDIFSTA_FIFOFAIL) {
			dbg(host, dbg_err, "FIFO failure\n");
			host->mrq->data->error = -EILSEQ;
			host->status = "error: 2440 fifo failure";
			goto fail_transfer;
		}
	} else {
		if (mci_dsta & S3C2410_SDIDSTA_FIFOFAIL) {
			dbg(host, dbg_err, "FIFO failure\n");
			cmd->data->error = -EILSEQ;
			host->status = "error:  fifo failure";
			goto fail_transfer;
		}
	}

	if (mci_dsta & S3C2410_SDIDSTA_RXCRCFAIL) {
		dbg(host, dbg_err, "bad data crc (outgoing)\n");
		cmd->data->error = -EILSEQ;
		host->status = "error: bad data crc (outgoing)";
		goto fail_transfer;
	}

	if (mci_dsta & S3C2410_SDIDSTA_CRCFAIL) {
		dbg(host, dbg_err, "bad data crc (incoming)\n");
		cmd->data->error = -EILSEQ;
		host->status = "error: bad data crc (incoming)";
		goto fail_transfer;
	}

	if (mci_dsta & S3C2410_SDIDSTA_DATATIMEOUT) {
		dbg(host, dbg_err, "data timeout\n");
		cmd->data->error = -ETIMEDOUT;
		host->status = "error: data timeout";
		goto fail_transfer;
	}

	if (mci_dsta & S3C2410_SDIDSTA_XFERFINISH) {
		if (host->complete_what == COMPLETION_XFERFINISH) {
			host->status = "ok: data transfer completed";
			goto close_transfer;
		}

		if (host->complete_what == COMPLETION_XFERFINISH_RSPFIN)
			host->complete_what = COMPLETION_RSPFIN;

		mci_dclear |= S3C2410_SDIDSTA_XFERFINISH;
	}

clear_status_bits:
	writel(mci_cclear, host->base + S3C2410_SDICMDSTAT);
	writel(mci_dclear, host->base + S3C2410_SDIDSTA);

	goto irq_out;

fail_transfer:
	host->pio_active = XFER_NONE;

close_transfer:
	host->complete_what = COMPLETION_FINALIZE;

	clear_imask(host);
	tasklet_schedule(&host->pio_tasklet);	//觸發tasklet

	goto irq_out;

irq_out:
	dbg(host, dbg_irq,
	    "csta:0x%08x dsta:0x%08x fsta:0x%08x dcnt:0x%08x status:%s.\n",
	    mci_csta, mci_dsta, mci_fsta, mci_dcnt, host->status);

	spin_unlock_irqrestore(&host->complete_lock, iflags);
	return IRQ_HANDLED;

}

static void pio_tasklet(unsigned long data)
{
	struct s3cmci_host *host = (struct s3cmci_host *) data;

	s3cmci_disable_irq(host, true);

	if (host->pio_active == XFER_WRITE)
		do_pio_write(host);

	if (host->pio_active == XFER_READ)
		do_pio_read(host);

	if (host->complete_what == COMPLETION_FINALIZE) {
		clear_imask(host);
		if (host->pio_active != XFER_NONE) {
			dbg(host, dbg_err, "unfinished %s "
			    "- pio_count:[%u] pio_bytes:[%u]\n",
			    (host->pio_active == XFER_READ) ? "read" : "write",
			    host->pio_count, host->pio_bytes);

			if (host->mrq->data)
				host->mrq->data->error = -EINVAL;
		}

		s3cmci_enable_irq(host, false);
		finalize_request(host);
	} else
		s3cmci_enable_irq(host, true);
}

再來看下數據發送：

static int s3cmci_prepare_dma(struct s3cmci_host *host, struct mmc_data *data)
{
	int dma_len, i;
	int rw = data->flags & MMC_DATA_WRITE;

	BUG_ON((data->flags & BOTH_DIR) == BOTH_DIR);

	s3cmci_dma_setup(host, rw ? S3C2410_DMASRC_MEM : S3C2410_DMASRC_HW);	//設置完成回調函數
	s3c2410_dma_ctrl(host->dma, S3C2410_DMAOP_FLUSH);

	dma_len = dma_map_sg(mmc_dev(host->mmc), data->sg, data->sg_len,
			     rw ? DMA_TO_DEVICE : DMA_FROM_DEVICE);

	if (dma_len == 0)
		return -ENOMEM;

	host->dma_complete = 0;
	host->dmatogo = dma_len;

	for (i = 0; i < dma_len; i++) {
		int res;

		dbg(host, dbg_dma, "enqueue %i: %08x@%u\n", i,
		    sg_dma_address(&data->sg[i]),
		    sg_dma_len(&data->sg[i]));

		res = s3c2410_dma_enqueue(host->dma, host,
					  sg_dma_address(&data->sg[i]),
					  sg_dma_len(&data->sg[i]));	//加載數據到DMA通道

		if (res) {
			s3c2410_dma_ctrl(host->dma, S3C2410_DMAOP_FLUSH);
			return -EBUSY;
		}
	}

	s3c2410_dma_ctrl(host->dma, S3C2410_DMAOP_START);	//開始DMA

	return 0;
}

static void s3cmci_dma_done_callback(struct s3c2410_dma_chan *dma_ch,
				     void *buf_id, int size,
				     enum s3c2410_dma_buffresult result)
{
	struct s3cmci_host *host = buf_id;
	unsigned long iflags;
	u32 mci_csta, mci_dsta, mci_fsta, mci_dcnt;

	mci_csta = readl(host->base + S3C2410_SDICMDSTAT);
	mci_dsta = readl(host->base + S3C2410_SDIDSTA);
	mci_fsta = readl(host->base + S3C2410_SDIFSTA);
	mci_dcnt = readl(host->base + S3C2410_SDIDCNT);

	BUG_ON(!host->mrq);
	BUG_ON(!host->mrq->data);
	BUG_ON(!host->dmatogo);

	spin_lock_irqsave(&host->complete_lock, iflags);

	if (result != S3C2410_RES_OK) {
		dbg(host, dbg_fail, "DMA FAILED: csta=0x%08x dsta=0x%08x "
			"fsta=0x%08x dcnt:0x%08x result:0x%08x toGo:%u\n",
			mci_csta, mci_dsta, mci_fsta,
			mci_dcnt, result, host->dmatogo);

		goto fail_request;
	}

	host->dmatogo--;
	if (host->dmatogo) {
		dbg(host, dbg_dma, "DMA DONE  Size:%i DSTA:[%08x] "
			"DCNT:[%08x] toGo:%u\n",
			size, mci_dsta, mci_dcnt, host->dmatogo);

		goto out;
	}

	dbg(host, dbg_dma, "DMA FINISHED Size:%i DSTA:%08x DCNT:%08x\n",
		size, mci_dsta, mci_dcnt);

	host->dma_complete = 1;
	host->complete_what = COMPLETION_FINALIZE;	//任務標記

out:
	tasklet_schedule(&host->pio_tasklet);	//觸發tasklet
	spin_unlock_irqrestore(&host->complete_lock, iflags);
	return;

fail_request:
	host->mrq->data->error = -EINVAL;
	host->complete_what = COMPLETION_FINALIZE;
	clear_imask(host);

	goto out;
}