linux-kernel - Re: [PATCH v2 04/10] coresight: trbe: Ensure the format flag is set on truncation

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Date:   Fri, 30 Jul 2021 09:56:34 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        coresight@...ts.linaro.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        tamas.zsoldos@....com, al.grant@....com, leo.yan@...aro.org,
        mike.leach@...aro.org, mathieu.poirier@...aro.org,
        jinlmao@....qualcomm.com
Subject: Re: [PATCH v2 04/10] coresight: trbe: Ensure the format flag is set
 on truncation



On 7/23/21 6:16 PM, Suzuki K Poulose wrote:
> When the TRBE is stopped on truncating an event, we may not
> set the FORMAT flag, even though the size of the record is 0.
> Let us be consistent and not confuse the user. Always set the
> format flag for TRBE generated records.
> 
> Cc: Anshuman Khandual <anshuman.khandual@....com>
> Cc: Leo Yan <leo.yan@...aro.org>
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  drivers/hwtracing/coresight/coresight-trbe.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
> index 176868496879..446f080f8320 100644
> --- a/drivers/hwtracing/coresight/coresight-trbe.c
> +++ b/drivers/hwtracing/coresight/coresight-trbe.c
> @@ -132,7 +132,8 @@ static void trbe_stop_and_truncate_event(struct perf_output_handle *handle)
>  	 * the update_buffer() to return a 0 size.
>  	 */
>  	trbe_drain_and_disable_local();
> -	perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> +	perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED |
> +				     PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW);
>  	*this_cpu_ptr(buf->cpudata->drvdata->handle) = NULL;
>  }

But why should not PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW also be set on
zero sized records as well ? Otherwise there are two instances during
TRBE buffer management, where PERF_AUX_FLAG_TRUNCATED is marked alone
without PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW. Those could be changed as
well.