[PATCH V2 2/3] dmaengine: zynqmp_dma: Add per-channel reset support

[Golla Nagendra]

Versal Gen 2 and Versal Net SoCs expose a dedicated reset line per
ZDMA channel, replacing the earlier approach where a single reset
was shared across all channels. Add reset handling in the channel
probe path using device_reset_optional() to trigger a reset pulse
on the channel during initialization.

Platforms without per-channel reset continue to work unaffected
since device_reset_optional() returns 0 when no reset is specified.

add pm_runtime_put_noidle() in the probe error path before
pm_runtime_disable() to balance the usage counter incremented by
pm_runtime_resume_and_get(). This is particularly important since
device_reset_optional() can return -EPROBE_DEFER, causing the
kernel to retry probe() and leak one PM usage count per retry
without the put.

Signed-off-by: Golla Nagendra <nagendra.golla at amd.com>
---
 drivers/dma/xilinx/zynqmp_dma.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
index f6a812e49ddc..a9dfec3c0ca3 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"
 
@@ -916,6 +917,11 @@ static int zynqmp_dma_chan_probe(struct zynqmp_dma_device *zdev,
 	if (IS_ERR(chan->regs))
 		return PTR_ERR(chan->regs);
 
+	err = device_reset_optional(&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;
@@ -1152,6 +1158,7 @@ static int zynqmp_dma_probe(struct platform_device *pdev)
 err_disable_pm:
 	if (!pm_runtime_enabled(zdev->dev))
 		zynqmp_dma_runtime_suspend(zdev->dev);
+	pm_runtime_put_noidle(zdev->dev);
 	pm_runtime_disable(zdev->dev);
 	return ret;
 }
-- 
2.34.1