Re: [PATCH v2 1/2] hwtracing: hisi_ptt: Propagate DMA reset timeout in trace_start()

[Yicong Yang <yangyccccc@gmail.com>]

+cc Suzuki and Sizhe..

On 2026/4/15 01:25, Pradhan, Sanman wrote:
> From: Sanman Pradhan <psanman@juniper.net>
>
> hisi_ptt_wait_dma_reset_done() discards the return value of
> readl_poll_timeout_atomic(). If the DMA engine does not complete its
> reset within the timeout, hisi_ptt_trace_start() proceeds to start
> tracing regardless.
>
> Return a bool from hisi_ptt_wait_dma_reset_done(), consistent with the
> other wait helpers in this driver. On timeout, log an error, de-assert
> the reset bit, and return -ETIMEDOUT. Move ctrl->started to the
> successful path so a failed start does not leave the trace marked as
> active.
>
> Fixes: ff0de066b463 ("hwtracing: hisi_ptt: Add trace function support for HiSilicon PCIe Tune and Trace device")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sanman Pradhan <psanman@juniper.net>

looks good to me.

Reviewed-by: Yicong Yang <yangyccccc@gmail.com>

I see the Suzuki has sent out the PR for 7.1, so this may wait after the merge window...

thanks.

> ---
> v2:
>   - Return bool for consistency with other wait helpers
>   - Add pci_err() on timeout
>   - De-assert RST before returning on timeout
>   - Move ctrl->started to the successful path
>
>  drivers/hwtracing/ptt/hisi_ptt.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/hwtracing/ptt/hisi_ptt.c b/drivers/hwtracing/ptt/hisi_ptt.c
> index 94c371c491357..b5d851281fbf0 100644
> --- a/drivers/hwtracing/ptt/hisi_ptt.c
> +++ b/drivers/hwtracing/ptt/hisi_ptt.c
> @@ -171,13 +171,13 @@ static bool hisi_ptt_wait_trace_hw_idle(struct hisi_ptt *hisi_ptt)
>  					  HISI_PTT_WAIT_TRACE_TIMEOUT_US);
>  }
>  
> -static void hisi_ptt_wait_dma_reset_done(struct hisi_ptt *hisi_ptt)
> +static bool hisi_ptt_wait_dma_reset_done(struct hisi_ptt *hisi_ptt)
>  {
>  	u32 val;
>  
> -	readl_poll_timeout_atomic(hisi_ptt->iobase + HISI_PTT_TRACE_WR_STS,
> -				  val, !val, HISI_PTT_RESET_POLL_INTERVAL_US,
> -				  HISI_PTT_RESET_TIMEOUT_US);
> +	return !readl_poll_timeout_atomic(hisi_ptt->iobase + HISI_PTT_TRACE_WR_STS,
> +					  val, !val, HISI_PTT_RESET_POLL_INTERVAL_US,
> +					  HISI_PTT_RESET_TIMEOUT_US);
>  }
>  
>  static void hisi_ptt_trace_end(struct hisi_ptt *hisi_ptt)
> @@ -202,14 +202,18 @@ static int hisi_ptt_trace_start(struct hisi_ptt *hisi_ptt)
>  		return -EBUSY;
>  	}
>  
> -	ctrl->started = true;
> -
>  	/* Reset the DMA before start tracing */
>  	val = readl(hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
>  	val |= HISI_PTT_TRACE_CTRL_RST;
>  	writel(val, hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
>  
> -	hisi_ptt_wait_dma_reset_done(hisi_ptt);
> +	if (!hisi_ptt_wait_dma_reset_done(hisi_ptt)) {
> +		pci_err(hisi_ptt->pdev, "timed out waiting for DMA reset\n");
> +		val = readl(hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
> +		val &= ~HISI_PTT_TRACE_CTRL_RST;
> +		writel(val, hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
> +		return -ETIMEDOUT;
> +	}
>  
>  	val = readl(hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);
>  	val &= ~HISI_PTT_TRACE_CTRL_RST;
> @@ -234,6 +238,8 @@ static int hisi_ptt_trace_start(struct hisi_ptt *hisi_ptt)
>  	if (!hisi_ptt->trace_ctrl.is_port)
>  		val |= HISI_PTT_TRACE_CTRL_FILTER_MODE;
>  
> +	ctrl->started = true;
> +
>  	/* Start the Trace */
>  	val |= HISI_PTT_TRACE_CTRL_EN;
>  	writel(val, hisi_ptt->iobase + HISI_PTT_TRACE_CTRL);