[PATCH V3 6/6] dmaengine: zynqmp_dma: Add per-channel reset support

[Golla Nagendra]

Versal Gen2 and Versal Net expose a dedicated reset line per ZDMA
channel. Use device_reset() to trigger a mandatory reset pulse on the
channel during probe when match data indicates reset is supported.

The has_reset field in zynqmp_dma_config controls whether reset is
performed for a given compatible. For Versal Net and Versal Gen2,
has_reset is set to true, so device_reset() is called and probe fails
if the resets property is missing in the device tree. For legacy SoCs,
match_data is NULL and has_reset defaults to false,so the reset path
is skipped entirely.

Signed-off-by: Golla Nagendra <nagendra.golla at amd.com>
---
Changes in V3:
- Introduce has_reset flag in zynqmp_dma_config to gate the reset path
  per-compatible instead of calling device_reset() unconditionally
- Move the of_device_get_match_data() call before the reset block so
  has_reset can be checked in the same code path that reads irq_offset
---
 drivers/dma/xilinx/zynqmp_dma.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
index 7561416b8e62..7ec6598ea587 100644
--- a/drivers/dma/xilinx/zynqmp_dma.c
+++ b/drivers/dma/xilinx/zynqmp_dma.c
@@ -18,6 +18,7 @@
 #include <linux/clk.h>
 #include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/pm_runtime.h>
+#include <linux/reset.h>
 
 #include "../dmaengine.h"
 
@@ -928,6 +929,14 @@ static int zynqmp_dma_chan_probe(struct zynqmp_dma_device *zdev,
 	if (IS_ERR(chan->regs))
 		return PTR_ERR(chan->regs);
 
+	match_data = of_device_get_match_data(&pdev->dev);
+	if (match_data && match_data->has_reset) {
+		err = device_reset(&pdev->dev);
+		if (err)
+			return dev_err_probe(&pdev->dev, err,
+					     "failed to reset channel\n");
+	}
+
 	chan->bus_width = ZYNQMP_DMA_BUS_WIDTH_64;
 	chan->dst_burst_len = ZYNQMP_DMA_MAX_DST_BURST_LEN;
 	chan->src_burst_len = ZYNQMP_DMA_MAX_SRC_BURST_LEN;
@@ -943,7 +952,6 @@ static int zynqmp_dma_chan_probe(struct zynqmp_dma_device *zdev,
 		return -EINVAL;
 	}
 
-	match_data = of_device_get_match_data(&pdev->dev);
 	if (match_data)
 		chan->irq_offset = match_data->offset;
 
-- 
2.43.7