[PATCH v2] dmaengine: zynqmp_dma: fix burst length configuration

[Matthias Fend <matthias.fend@xxxxxxxxxxxxxx>]

Since the dma engine expects the burst length register content as
power of 2 value, the burst length needs to be converted first.
Additionally add a burst length range check to avoid corrupting unrelated
register bits.

Signed-off-by: Matthias Fend <matthias.fend@xxxxxxxxxxxxxx>
---
 drivers/dma/xilinx/zynqmp_dma.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
index 9c845c07b107..d47749a35863 100644
--- a/drivers/dma/xilinx/zynqmp_dma.c
+++ b/drivers/dma/xilinx/zynqmp_dma.c
@@ -123,10 +123,12 @@
 /* Max transfer size per descriptor */
 #define ZYNQMP_DMA_MAX_TRANS_LEN	0x40000000
 
+/* Max burst lengths */
+#define ZYNQMP_DMA_MAX_DST_BURST_LEN    32768U
+#define ZYNQMP_DMA_MAX_SRC_BURST_LEN    32768U
+
 /* Reset values for data attributes */
 #define ZYNQMP_DMA_AXCACHE_VAL		0xF
-#define ZYNQMP_DMA_ARLEN_RST_VAL	0xF
-#define ZYNQMP_DMA_AWLEN_RST_VAL	0xF
 
 #define ZYNQMP_DMA_SRC_ISSUE_RST_VAL	0x1F
 
@@ -534,17 +536,19 @@ static void zynqmp_dma_handle_ovfl_int(struct zynqmp_dma_chan *chan, u32 status)
 
 static void zynqmp_dma_config(struct zynqmp_dma_chan *chan)
 {
-	u32 val;
+	u32 val, burst_val;
 
 	val = readl(chan->regs + ZYNQMP_DMA_CTRL0);
 	val |= ZYNQMP_DMA_POINT_TYPE_SG;
 	writel(val, chan->regs + ZYNQMP_DMA_CTRL0);
 
 	val = readl(chan->regs + ZYNQMP_DMA_DATA_ATTR);
+	burst_val = __ilog2_u32(chan->src_burst_len);
 	val = (val & ~ZYNQMP_DMA_ARLEN) |
-		(chan->src_burst_len << ZYNQMP_DMA_ARLEN_OFST);
+		((burst_val << ZYNQMP_DMA_ARLEN_OFST) & ZYNQMP_DMA_ARLEN);
+	burst_val = __ilog2_u32(chan->dst_burst_len);
 	val = (val & ~ZYNQMP_DMA_AWLEN) |
-		(chan->dst_burst_len << ZYNQMP_DMA_AWLEN_OFST);
+		((burst_val << ZYNQMP_DMA_AWLEN_OFST) & ZYNQMP_DMA_AWLEN);
 	writel(val, chan->regs + ZYNQMP_DMA_DATA_ATTR);
 }
 
@@ -560,8 +564,10 @@ static int zynqmp_dma_device_config(struct dma_chan *dchan,
 {
 	struct zynqmp_dma_chan *chan = to_chan(dchan);
 
-	chan->src_burst_len = config->src_maxburst;
-	chan->dst_burst_len = config->dst_maxburst;
+	chan->src_burst_len = clamp(config->src_maxburst, 1U,
+		ZYNQMP_DMA_MAX_SRC_BURST_LEN);
+	chan->dst_burst_len = clamp(config->dst_maxburst, 1U,
+		ZYNQMP_DMA_MAX_DST_BURST_LEN);
 
 	return 0;
 }
@@ -887,8 +893,8 @@ static int zynqmp_dma_chan_probe(struct zynqmp_dma_device *zdev,
 		return PTR_ERR(chan->regs);
 
 	chan->bus_width = ZYNQMP_DMA_BUS_WIDTH_64;
-	chan->dst_burst_len = ZYNQMP_DMA_AWLEN_RST_VAL;
-	chan->src_burst_len = ZYNQMP_DMA_ARLEN_RST_VAL;
+	chan->dst_burst_len = ZYNQMP_DMA_MAX_DST_BURST_LEN;
+	chan->src_burst_len = ZYNQMP_DMA_MAX_SRC_BURST_LEN;
 	err = of_property_read_u32(node, "xlnx,bus-width", &chan->bus_width);
 	if (err < 0) {
 		dev_err(&pdev->dev, "missing xlnx,bus-width property\n");
-- 
2.17.1