[PATCH V1] dmaengine: xdma: Check zero length scatter list segment

[Lizhi Hou <lizhi.hou@amd.com>]

In callback function xdma_prep_device_sg(), it is nice to check if there
is zero length segment and skip it in the input scatter list.

Reported-by: Martin Tuma <tumic@gpxsee.org>
Link: https://lore.kernel.org/dmaengine/f6a0051f-acec-f661-55cb-8b2504bef79e@amd.com/T/#t
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
---
 drivers/dma/xilinx/xdma.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
index 462109c61653..5134757e88b1 100644
--- a/drivers/dma/xilinx/xdma.c
+++ b/drivers/dma/xilinx/xdma.c
@@ -465,6 +465,8 @@ xdma_prep_device_sg(struct dma_chan *chan, struct scatterlist *sgl,
 
 	for_each_sg(sgl, sg, sg_len, i)
 		desc_num += DIV_ROUND_UP(sg_dma_len(sg), XDMA_DESC_BLEN_MAX);
+	if (!desc_num)
+		return NULL;
 
 	sw_desc = xdma_alloc_desc(xdma_chan, desc_num);
 	if (!sw_desc)
@@ -488,7 +490,7 @@ xdma_prep_device_sg(struct dma_chan *chan, struct scatterlist *sgl,
 		addr = sg_dma_address(sg);
 		rest = sg_dma_len(sg);
 
-		do {
+		while (rest) {
 			len = min_t(u32, rest, XDMA_DESC_BLEN_MAX);
 			/* set hardware descriptor */
 			desc->bytes = cpu_to_le32(len);
@@ -506,7 +508,7 @@ xdma_prep_device_sg(struct dma_chan *chan, struct scatterlist *sgl,
 			dev_addr += len;
 			addr += len;
 			rest -= len;
-		} while (rest);
+		};
 	}
 
 	tx_desc = vchan_tx_prep(&xdma_chan->vchan, &sw_desc->vdesc, flags);
-- 
2.27.0