[PATCH 3/4] dmaengine: xilinx: dpdma: Print debug message when losing vsync race

[Laurent Pinchart]

The hardware retrigger is inherently racy with the vsync interrupt. This
isn't an issue as the hardware provides a way to detect a race loss and
handle it correctly. When debugging issues related to this, it's useful
to get a notification of the race loss. Add a debug message to do so.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 drivers/dma/xilinx/xilinx_dpdma.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/xilinx/xilinx_dpdma.c b/drivers/dma/xilinx/xilinx_dpdma.c
index ea56c3b35782..5834f8614a58 100644
--- a/drivers/dma/xilinx/xilinx_dpdma.c
+++ b/drivers/dma/xilinx/xilinx_dpdma.c
@@ -1095,8 +1095,12 @@ static void xilinx_dpdma_chan_vsync_irq(struct  xilinx_dpdma_chan *chan)
 	/* If the retrigger raced with vsync, retry at the next frame. */
 	sw_desc = list_first_entry(&pending->descriptors,
 				   struct xilinx_dpdma_sw_desc, node);
-	if (sw_desc->hw.desc_id != desc_id)
+	if (sw_desc->hw.desc_id != desc_id) {
+		dev_dbg(chan->xdev->dev,
+			"chan%u: vsync race lost (%u != %u), retrying\n",
+			chan->id, sw_desc->hw.desc_id, desc_id);
 		goto out;
+	}
 
 	/*
 	 * Complete the active descriptor, if any, promote the pending
-- 
Regards,

Laurent Pinchart