Re: [PATCH v2 16/23] coresight: trbe: Always classify TRBSR when updating buffer

[James Clark <james.clark@linaro.org>]

On 16/10/2026 17:55, Leo Yan wrote:
> arm_trbe_update_buffer() must account trace when perf stops a session,
> even if no maintenance interrupt has been handled. Prepare it for
> trigger and wrap modes by making the trace-size decision from the
> drained TRBSR status rather than gating classification on IRQ.
> Acknowledge IRQ only when it is set.
> 
> In FILL mode, reaching LIMIT sets WRAP and IRQ and returns TRBPTR to
> BASE. Interrupt delivery can be delayed, so update_buffer() may run
> before the IRQ handler. The existing IRQ-gated path uses WRAP to size
> through LIMIT in that case; preserve this while also classifying
> updates without a pending IRQ.
> 
> With classification on the no-IRQ path, a normal software stop can
> have TRBSR.S clear and an ignored detected trigger can set TRBSR.TRG.
> Neither should warn or discard valid trace. Mark fatal status as
> truncated and return zero. Use LIMIT for a filled WRAP and TRBPTR
> otherwise.
> 
> Signed-off-by: Leo Yan <leo.yan@arm.com>
> ---
>   drivers/hwtracing/coresight/coresight-trbe.c | 24 +++++++++---------------
>   1 file changed, 9 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
> index ac49098aa08412a23a20d32f84c2e1977ee4a223..661f4a78e67c30652de8c834e4773819fa67b5ac 100644
> --- a/drivers/hwtracing/coresight/coresight-trbe.c
> +++ b/drivers/hwtracing/coresight/coresight-trbe.c
> @@ -662,8 +662,6 @@ static enum trbe_fault_action trbe_get_fault_act(struct perf_output_handle *hand
>   	int ec = get_trbe_ec(trbsr);
>   	int bsc = get_trbe_bsc(trbsr);
>   
> -	WARN_ON(is_trbe_running(trbsr));
> -
>   	if (is_trbe_abort(trbsr)) {
>   		err_str = "External abort";
>   		goto out_fatal;
> @@ -844,7 +842,6 @@ static unsigned long arm_trbe_update_buffer(struct coresight_device *csdev,
>   	enum trbe_fault_action act;
>   	unsigned long size, status;
>   	unsigned long flags;
> -	bool wrap = false;
>   
>   	WARN_ON(buf->cpudata != cpudata);
>   	WARN_ON(cpudata->cpu != smp_processor_id());
> @@ -896,23 +893,20 @@ static unsigned long arm_trbe_update_buffer(struct coresight_device *csdev,
>   		 */
>   		clr_trbe_irq();
>   		isb();
> +	}
>   
> -		act = trbe_get_fault_act(handle, status);
> -		/*
> -		 * If this was not due to a WRAP event, we have some
> -		 * errors and as such buffer is empty.
> -		 */
> -		if (act != TRBE_FAULT_ACT_WRAP) {
> -			perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> -			size = 0;
> -			goto done;
> -		}
> +	act = trbe_get_fault_act(handle, status);
>   
> +	/* If an error occurred, the buffer may be empty */
> +	if (act == TRBE_FAULT_ACT_FATAL) {
> +		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> +		size = 0;
> +		goto done;
> +	} else if (act == TRBE_FAULT_ACT_WRAP) {
>   		trbe_report_wrap_event(handle);
> -		wrap = true;
>   	}
>   
> -	size = trbe_get_trace_size(handle, buf, wrap);
> +	size = trbe_get_trace_size(handle, buf, act == TRBE_FAULT_ACT_WRAP);
>   
>   done:
>   	local_irq_restore(flags);
> 
Reviewed-by: James Clark <james.clark@linaro.org>