Re: [PATCH 2/2] hwtracing: hisi_ptt: Remove unnecessary trace buffer zeroing in trace_start()

[Yicong Yang <yangyccccc@gmail.com>]

On 2026/4/9 09:07, Pradhan, Sanman wrote:
> From: Sanman Pradhan <psanman@juniper.net>
>
> hisi_ptt_trace_start() clears all four trace buffers before enabling
> tracing.
>
> This is unnecessary. On trace stop, hisi_ptt_update_aux() copies only
> the number of bytes reported in HISI_PTT_TRACE_WR_STS. On buffer-full
> interrupts, it copies a full completed buffer. In both cases the driver
> only consumes data written by hardware.
>
> Remove the buffer clearing from the trace start path.
>
> Signed-off-by: Sanman Pradhan <psanman@juniper.net>

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

> ---
>  drivers/hwtracing/ptt/hisi_ptt.c | 5 -----
>  1 file changed, 5 deletions(-)
>
> diff --git a/drivers/hwtracing/ptt/hisi_ptt.c b/drivers/hwtracing/ptt/hisi_ptt.c
> index 73b93df8504c4..cbfbd1f146ba3 100644
> --- a/drivers/hwtracing/ptt/hisi_ptt.c
> +++ b/drivers/hwtracing/ptt/hisi_ptt.c
> @@ -195,7 +195,6 @@ static int hisi_ptt_trace_start(struct hisi_ptt *hisi_ptt)
>  	struct hisi_ptt_trace_ctrl *ctrl = &hisi_ptt->trace_ctrl;
>  	u32 val;
>  	int ret;
> -	int i;
>  
>  	/* Check device idle before start trace */
>  	if (!hisi_ptt_wait_trace_hw_idle(hisi_ptt)) {
> @@ -221,10 +220,6 @@ static int hisi_ptt_trace_start(struct hisi_ptt *hisi_ptt)
>  	/* Reset the index of current buffer */
>  	hisi_ptt->trace_ctrl.buf_index = 0;
>  
> -	/* Zero the trace buffers */
> -	for (i = 0; i < HISI_PTT_TRACE_BUF_CNT; i++)
> -		memset(ctrl->trace_buf[i].addr, 0, HISI_PTT_TRACE_BUF_SIZE);
> -
>  	/* Clear the interrupt status */
>  	writel(HISI_PTT_TRACE_INT_STAT_MASK, hisi_ptt->iobase + HISI_PTT_TRACE_INT_STAT);
>  	writel(0, hisi_ptt->iobase + HISI_PTT_TRACE_INT_MASK);