dmaengine: xilinx: dpdma: Print debug message when losing vsync race

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@ideasonboard.com>
Tested-by: Jianqiang Chen <jianqiang.chen@xilinx.com>
Reviewed-by: Jianqiang Chen <jianqiang.chen@xilinx.com>
Link: https://lore.kernel.org/r/20210520152420.23986-4-laurent.pinchart@ideasonboard.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/xilinx/xilinx_dpdma.c b/drivers/dma/xilinx/xilinx_dpdma.c
index ea56c3b..5834f86 100644 (file)
--- 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