[PATCH 4/4] dmaengine: xilinx: dpdma: Limit descriptor IDs to 16 bits

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

While the descriptor ID is stored in a 32-bit field in the hardware
descriptor, only 16 bits are used by the hardware and are reported
through the XILINX_DPDMA_CH_DESC_ID register. Failure to handle the
wrap-around results in a descriptor ID mismatch after 65536 frames. Fix
it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/dma/xilinx/xilinx_dpdma.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/xilinx/xilinx_dpdma.c b/drivers/dma/xilinx/xilinx_dpdma.c
index 5834f8614a58..6a8bb977fc7a 100644
--- a/drivers/dma/xilinx/xilinx_dpdma.c
+++ b/drivers/dma/xilinx/xilinx_dpdma.c
@@ -113,6 +113,7 @@
 #define XILINX_DPDMA_CH_VDO				0x020
 #define XILINX_DPDMA_CH_PYLD_SZ				0x024
 #define XILINX_DPDMA_CH_DESC_ID				0x028
+#define XILINX_DPDMA_CH_DESC_ID_MASK			GENMASK(15, 0)
 
 /* DPDMA descriptor fields */
 #define XILINX_DPDMA_DESC_CONTROL_PREEMBLE		0xa5
@@ -867,7 +868,8 @@ static void xilinx_dpdma_chan_queue_transfer(struct xilinx_dpdma_chan *chan)
 	 * will be used, but it should be enough.
 	 */
 	list_for_each_entry(sw_desc, &desc->descriptors, node)
-		sw_desc->hw.desc_id = desc->vdesc.tx.cookie;
+		sw_desc->hw.desc_id = desc->vdesc.tx.cookie
+				    & XILINX_DPDMA_CH_DESC_ID_MASK;
 
 	sw_desc = list_first_entry(&desc->descriptors,
 				   struct xilinx_dpdma_sw_desc, node);
@@ -1090,7 +1092,8 @@ static void xilinx_dpdma_chan_vsync_irq(struct  xilinx_dpdma_chan *chan)
 	if (!chan->running || !pending)
 		goto out;
 
-	desc_id = dpdma_read(chan->reg, XILINX_DPDMA_CH_DESC_ID);
+	desc_id = dpdma_read(chan->reg, XILINX_DPDMA_CH_DESC_ID)
+		& XILINX_DPDMA_CH_DESC_ID_MASK;
 
 	/* If the retrigger raced with vsync, retry at the next frame. */
 	sw_desc = list_first_entry(&pending->descriptors,
-- 
Regards,

Laurent Pinchart