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

[Frank Li]

On Thu, Jun 18, 2026 at 12:40:55PM +0530, Golla Nagendra wrote:
> [You don't often get email from nagendra.golla@xxxxxxx. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
>
> 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.

Use sperate patch to fix this problem

Frank
>
> Signed-off-by: Golla Nagendra <nagendra.golla@xxxxxxx>
> ---
>  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
>