[PATCH 4/5] dmaengine: xilinx: xdma: Rework xdma_channel_isr()

[Jan Kuliga]

The xdma's channel status register may be read and cleared
simultaneously, by accessing it via separate XDMA_CHAN_STATUS_RC
register. Therefore, it is possible to simplify the code
by just getting rid of a separate redundant write.

Also, implement the actual status register checking as well.
Previously, the cyclic callback would be scheduled regardless of the
status register state. Fix it.

Signed-off-by: Jan Kuliga <jankul@xxxxxxxxxxxxxxxx>
---
 drivers/dma/xilinx/xdma-regs.h |  2 ++
 drivers/dma/xilinx/xdma.c      | 17 +++++++++--------
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/dma/xilinx/xdma-regs.h b/drivers/dma/xilinx/xdma-regs.h
index 654c5e41112d..6bf7ae84e452 100644
--- a/drivers/dma/xilinx/xdma-regs.h
+++ b/drivers/dma/xilinx/xdma-regs.h
@@ -116,6 +116,8 @@ struct xdma_hw_desc {
 			 CHAN_CTRL_IE_WRITE_ERROR |			\
 			 CHAN_CTRL_IE_DESC_ERROR)
 
+#define XDMA_CHAN_STATUS_MASK CHAN_CTRL_START
+
 /* bits of the channel interrupt enable mask */
 #define CHAN_IM_DESC_ERROR			BIT(19)
 #define CHAN_IM_READ_ERROR			BIT(9)
diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
index 58539a093de2..dc7f43f17103 100644
--- a/drivers/dma/xilinx/xdma.c
+++ b/drivers/dma/xilinx/xdma.c
@@ -809,15 +809,16 @@ static irqreturn_t xdma_channel_isr(int irq, void *dev_id)
 
 	desc->completed_desc_num += complete_desc_num;
 
-	if (desc->cyclic) {
-		ret = regmap_read(xdev->rmap, xchan->base + XDMA_CHAN_STATUS,
-				  &st);
-		if (ret)
-			goto out;
-
-		regmap_write(xdev->rmap, xchan->base + XDMA_CHAN_STATUS, st);
+	/* clear-on-read the status register */
+	ret = regmap_read(xdev->rmap, xchan->base + XDMA_CHAN_STATUS_RC,
+			  &st);
+	if (ret)
+		goto out;
 
-		vchan_cyclic_callback(vd);
+	if (desc->cyclic) {
+		st &= XDMA_CHAN_STATUS_MASK;
+		if (st & CHAN_CTRL_IE_DESC_COMPLETED)
+			vchan_cyclic_callback(vd);
 		goto out;
 	}
 
-- 
2.34.1