mmc: dw_mmc: fix stop when fallen back to PIO

There are several situations when dw_mci_submit_data_dma() decides to
fall back to PIO mode instead of using DMA, due to a short (to avoid
overhead) or "complex" (e.g. with unaligned buffers) transaction, even
though host->use_dma is set. However dw_mci_stop_dma() decides whether
to stop DMA or set the EVENT_XFER_COMPLETE event based on host->use_dma.
When falling back to PIO mode this results in data timeout errors
getting missed and the driver locking up.

Therefore add host->using_dma to indicate whether the current
transaction is using dma or not, and adjust dw_mci_stop_dma() to use
that instead.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Acked-by: Will Newton <will.newton@imgtec.com>
Tested-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/dw_mmc.c

@@ -287,7 +287,7 @@ static void send_stop_cmd(struct dw_mci *host, struct mmc_data *data)
 /* DMA interface functions */
 static void dw_mci_stop_dma(struct dw_mci *host)
 {
-	if (host->use_dma) {
+	if (host->using_dma) {
 		host->dma_ops->stop(host);
 		host->dma_ops->cleanup(host);
 	} else {
@@ -435,6 +435,8 @@ static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)
 	unsigned int i, direction, sg_len;
 	u32 temp;
 
+	host->using_dma = 0;
+
 	/* If we don't have a channel, we can't do DMA */
 	if (!host->use_dma)
 		return -ENODEV;
@@ -454,6 +456,8 @@ static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)
 			return -EINVAL;
 	}
 
+	host->using_dma = 1;
+
 	if (data->flags & MMC_DATA_READ)
 		direction = DMA_FROM_DEVICE;
 	else

include/linux/mmc/dw_mmc.h

@@ -48,6 +48,7 @@ struct mmc_data;
  * @data: The data currently being transferred, or NULL if no data
  *	transfer is in progress.
  * @use_dma: Whether DMA channel is initialized or not.
+ * @using_dma: Whether DMA is in use for the current transfer.
  * @sg_dma: Bus address of DMA buffer.
  * @sg_cpu: Virtual address of DMA buffer.
  * @dma_ops: Pointer to platform-specific DMA callbacks.
@@ -121,6 +122,7 @@ struct dw_mci {
 
 	/* DMA interface members*/
 	int			use_dma;
+	int			using_dma;
 
 	dma_addr_t		sg_dma;
 	void			*sg_cpu;