[PATCH] dmaengine: stm32-mdma: correct desc prep when channel running

[Amelie Delaunay]

From: Alain Volmat <alain.volmat at foss.st.com>

In case of the prep descriptor while the channel is already running, the
CCR register value stored into the channel could already have its EN bit
set.  This would lead to a bad transfer since, at start transfer time,
enabling the channel while other registers aren't yet properly set.
To avoid this, ensure to mask the CCR_EN bit when storing the ccr value
into the mdma channel structure.

Fixes: a4ffb13c8946 ("dmaengine: Add STM32 MDMA driver")
Signed-off-by: Alain Volmat <alain.volmat at foss.st.com>
Signed-off-by: Amelie Delaunay <amelie.delaunay at foss.st.com>
Cc: stable at vger.kernel.org
---
 drivers/dma/stm32-mdma.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/stm32-mdma.c b/drivers/dma/stm32-mdma.c
index bae08b3f55c7..f414efdbd809 100644
--- a/drivers/dma/stm32-mdma.c
+++ b/drivers/dma/stm32-mdma.c
@@ -489,7 +489,7 @@ static int stm32_mdma_set_xfer_param(struct stm32_mdma_chan *chan,
 	src_maxburst = chan->dma_config.src_maxburst;
 	dst_maxburst = chan->dma_config.dst_maxburst;
 
-	ccr = stm32_mdma_read(dmadev, STM32_MDMA_CCR(chan->id));
+	ccr = stm32_mdma_read(dmadev, STM32_MDMA_CCR(chan->id)) & ~STM32_MDMA_CCR_EN;
 	ctcr = stm32_mdma_read(dmadev, STM32_MDMA_CTCR(chan->id));
 	ctbr = stm32_mdma_read(dmadev, STM32_MDMA_CTBR(chan->id));
 
@@ -965,7 +965,7 @@ stm32_mdma_prep_dma_memcpy(struct dma_chan *c, dma_addr_t dest, dma_addr_t src,
 	if (!desc)
 		return NULL;
 
-	ccr = stm32_mdma_read(dmadev, STM32_MDMA_CCR(chan->id));
+	ccr = stm32_mdma_read(dmadev, STM32_MDMA_CCR(chan->id)) & ~STM32_MDMA_CCR_EN;
 	ctcr = stm32_mdma_read(dmadev, STM32_MDMA_CTCR(chan->id));
 	ctbr = stm32_mdma_read(dmadev, STM32_MDMA_CTBR(chan->id));
 	cbndtr = stm32_mdma_read(dmadev, STM32_MDMA_CBNDTR(chan->id));
-- 
2.25.1