mmc: mxcmmc: fix bug that may block a data transfer forever

The problem can be easily reproduced using a script that loops
copying a file in an SD card to another place in the same SD card
and its related to read transfers. This only happens with DMA enabled.

This is related to the fact that, when reading, an MMC irq signals
the fact that all data from the SD card has been copied to the
internal buffers. However, it doesn't signal whether the DMA transfer
that is in charge of moving data from these internal buffers to RAM
has finished or not. Thus, calling dmaengine_terminate_all() in the
MMC irq routine can cancel an ongoing DMA transfer leaving some data
in the internal buffers that produces an accumulative effect which,
in the end, blocks a read data transfer forever.

The following patch watches DMA irq for reading and MMC irqs for
writing transfers. The 'dangerous' usage of dmaengine_terminate_all()
is removed and a timeout of 10 seconds is added so that the MMC won't
block forever anymore.
Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/mxcmmc.c

@@ -44,6 +44,7 @@
 #include <mach/hardware.h>
 
 #define DRIVER_NAME "mxc-mmc"
+#define MXCMCI_TIMEOUT_MS 10000
 
 #define MMC_REG_STR_STP_CLK		0x00
 #define MMC_REG_STATUS			0x04
@@ -150,6 +151,8 @@ struct mxcmci_host {
 	int			dmareq;
 	struct dma_slave_config dma_slave_config;
 	struct imx_dma_data	dma_data;
+
+	struct timer_list	watchdog;
 };
 
 static void mxcmci_set_clk_rate(struct mxcmci_host *host, unsigned int clk_ios);
@@ -271,9 +274,32 @@ static int mxcmci_setup_data(struct mxcmci_host *host, struct mmc_data *data)
 	dmaengine_submit(host->desc);
 	dma_async_issue_pending(host->dma);
 
+	mod_timer(&host->watchdog, jiffies + msecs_to_jiffies(MXCMCI_TIMEOUT_MS));
+
 	return 0;
 }
 
+static void mxcmci_cmd_done(struct mxcmci_host *host, unsigned int stat);
+static void mxcmci_data_done(struct mxcmci_host *host, unsigned int stat);
+
+static void mxcmci_dma_callback(void *data)
+{
+	struct mxcmci_host *host = data;
+	u32 stat;
+
+	del_timer(&host->watchdog);
+
+	stat = readl(host->base + MMC_REG_STATUS);
+	writel(stat & ~STATUS_DATA_TRANS_DONE, host->base + MMC_REG_STATUS);
+
+	dev_dbg(mmc_dev(host->mmc), "%s: 0x%08x\n", __func__, stat);
+
+	if (stat & STATUS_READ_OP_DONE)
+		writel(STATUS_READ_OP_DONE, host->base + MMC_REG_STATUS);
+
+	mxcmci_data_done(host, stat);
+}
+
 static int mxcmci_start_cmd(struct mxcmci_host *host, struct mmc_command *cmd,
 		unsigned int cmdat)
 {
@@ -305,8 +331,14 @@ static int mxcmci_start_cmd(struct mxcmci_host *host, struct mmc_command *cmd,
 
 	int_cntr = INT_END_CMD_RES_EN;
 
-	if (mxcmci_use_dma(host))
-		int_cntr |= INT_READ_OP_EN | INT_WRITE_OP_DONE_EN;
+	if (mxcmci_use_dma(host)) {
+		if (host->dma_dir == DMA_FROM_DEVICE) {
+			host->desc->callback = mxcmci_dma_callback;
+			host->desc->callback_param = host;
+		} else {
+			int_cntr |= INT_WRITE_OP_DONE_EN;
+		}
+	}
 
 	spin_lock_irqsave(&host->lock, flags);
 	if (host->use_sdio)
@@ -345,11 +377,9 @@ static int mxcmci_finish_data(struct mxcmci_host *host, unsigned int stat)
 	struct mmc_data *data = host->data;
 	int data_error;
 
-	if (mxcmci_use_dma(host)) {
-		dmaengine_terminate_all(host->dma);
+	if (mxcmci_use_dma(host))
 		dma_unmap_sg(host->dma->device->dev, data->sg, data->sg_len,
 				host->dma_dir);
-	}
 
 	if (stat & STATUS_ERR_MASK) {
 		dev_dbg(mmc_dev(host->mmc), "request failed. status: 0x%08x\n",
@@ -624,8 +654,10 @@ static irqreturn_t mxcmci_irq(int irq, void *devid)
 		mxcmci_cmd_done(host, stat);
 
 	if (mxcmci_use_dma(host) &&
-		  (stat & (STATUS_DATA_TRANS_DONE | STATUS_WRITE_OP_DONE)))
+		  (stat & (STATUS_DATA_TRANS_DONE | STATUS_WRITE_OP_DONE))) {
+		del_timer(&host->watchdog);
 		mxcmci_data_done(host, stat);
+	}
 
 	if (host->default_irq_mask &&
 		  (stat & (STATUS_CARD_INSERTION | STATUS_CARD_REMOVAL)))
@@ -836,6 +868,34 @@ static bool filter(struct dma_chan *chan, void *param)
 	return true;
 }
 
+static void mxcmci_watchdog(unsigned long data)
+{
+	struct mmc_host *mmc = (struct mmc_host *)data;
+	struct mxcmci_host *host = mmc_priv(mmc);
+	struct mmc_request *req = host->req;
+	unsigned int stat = readl(host->base + MMC_REG_STATUS);
+
+	if (host->dma_dir == DMA_FROM_DEVICE) {
+		dmaengine_terminate_all(host->dma);
+		dev_err(mmc_dev(host->mmc),
+			"%s: read time out (status = 0x%08x)\n",
+			__func__, stat);
+	} else {
+		dev_err(mmc_dev(host->mmc),
+			"%s: write time out (status = 0x%08x)\n",
+			__func__, stat);
+		mxcmci_softreset(host);
+	}
+
+	/* Mark transfer as erroneus and inform the upper layers */
+
+	host->data->error = -ETIMEDOUT;
+	host->req = NULL;
+	host->cmd = NULL;
+	host->data = NULL;
+	mmc_request_done(host->mmc, req);
+}
+
 static const struct mmc_host_ops mxcmci_ops = {
 	.request		= mxcmci_request,
 	.set_ios		= mxcmci_set_ios,
@@ -968,6 +1028,10 @@ static int mxcmci_probe(struct platform_device *pdev)
 
 	mmc_add_host(mmc);
 
+	init_timer(&host->watchdog);
+	host->watchdog.function = &mxcmci_watchdog;
+	host->watchdog.data = (unsigned long)mmc;
+
 	return 0;
 
 out_free_irq: