[PATCH 3.2 034/149] mmc: tmio_mmc_dma: fix PIO fallback on SDHI

[Ben Hutchings]

3.2.52-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>

commit f936f9b67b7f8c2eae01dd303a0e90bd777c4679 upstream.

I'm testing SH-Mobile SDHI driver in DMA mode with  a new DMA controller  using
'bonnie++' and getting DMA error after which the tmio_mmc_dma.c code falls back
to PIO but all commands time out after that.  It turned out that the fallback
code calls tmio_mmc_enable_dma() with RX/TX channels already freed and pointers
to them cleared, so that the function bails out early instead  of clearing the
DMA bit in the CTL_DMA_ENABLE register. The regression was introduced by commit
162f43e31c5a376ec16336e5d0ac973373d54c89 (mmc: tmio: fix a deadlock).
Moving tmio_mmc_enable_dma() calls to the top of the PIO fallback code in
tmio_mmc_start_dma_{rx|tx}() helps.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
Signed-off-by: Chris Ball <cjb@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/mmc/host/tmio_mmc_dma.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/mmc/host/tmio_mmc_dma.c
+++ b/drivers/mmc/host/tmio_mmc_dma.c
@@ -92,6 +92,7 @@ static void tmio_mmc_start_dma_rx(struct
 pio:
 	if (!desc) {
 		/* DMA failed, fall back to PIO */
+		tmio_mmc_enable_dma(host, false);
 		if (ret >= 0)
 			ret = -EIO;
 		host->chan_rx = NULL;
@@ -104,7 +105,6 @@ pio:
 		}
 		dev_warn(&host->pdev->dev,
 			 "DMA failed: %d, falling back to PIO\n", ret);
-		tmio_mmc_enable_dma(host, false);
 	}
 
 	dev_dbg(&host->pdev->dev, "%s(): desc %p, cookie %d, sg[%d]\n", __func__,
@@ -173,6 +173,7 @@ static void tmio_mmc_start_dma_tx(struct
 pio:
 	if (!desc) {
 		/* DMA failed, fall back to PIO */
+		tmio_mmc_enable_dma(host, false);
 		if (ret >= 0)
 			ret = -EIO;
 		host->chan_tx = NULL;
@@ -185,7 +186,6 @@ pio:
 		}
 		dev_warn(&host->pdev->dev,
 			 "DMA failed: %d, falling back to PIO\n", ret);
-		tmio_mmc_enable_dma(host, false);
 	}
 
 	dev_dbg(&host->pdev->dev, "%s(): desc %p, cookie %d\n", __func__,

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