linux-kernel - Re: [PATCH V3 12/18] coresight: tmc: dump system memory content only when needed

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Date:	Mon, 25 Apr 2016 12:16:37 +0100
From:	Suzuki K Poulose <Suzuki.Poulose@....com>
To:	Mathieu Poirier <mathieu.poirier@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 12/18] coresight: tmc: dump system memory content only
 when needed

On 22/04/16 18:14, Mathieu Poirier wrote:
> Calling tmc_etf/etr_dump_hw() is required only when operating from
> sysFS.  When working from Perf, the system memory is harvested
> from the AUX trace API.
>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> ---
>   drivers/hwtracing/coresight/coresight-tmc-etf.c | 7 ++++++-
>   drivers/hwtracing/coresight/coresight-tmc-etr.c | 7 ++++++-
>   2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index d090a9745c73..25fad93b68d4 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -74,7 +74,12 @@ static void tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
>   	CS_UNLOCK(drvdata->base);
>
>   	tmc_flush_and_stop(drvdata);
> -	tmc_etb_dump_hw(drvdata);
> +	/*
> +	 * When operating in sysFS mode the content of the buffer needs to be
> +	 * read before the TMC is disabled.
> +	 */
> +	if (local_read(&drvdata->mode) == CS_MODE_SYSFS)
> +		tmc_etb_dump_hw(drvdata);
>   	tmc_disable_hw(drvdata);
>
>   	CS_LOCK(drvdata->base);
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index 8bbbf3ab1387..4b000f4003a2 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -76,7 +76,12 @@ static void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
>   	CS_UNLOCK(drvdata->base);
>
>   	tmc_flush_and_stop(drvdata);
> -	tmc_etr_dump_hw(drvdata);
> +	/*
> +	 * When operating in sysFS mode the content of the buffer needs to be
> +	 * read before the TMC is disabled.
> +	 */
> +	if (local_read(&drvdata->mode) == CS_MODE_SYSFS)
> +		tmc_etr_dump_hw(drvdata);
>   	tmc_disable_hw(drvdata);

Nit: It would be cleaner if tmc_etX_disable_hw accepted a bool parameter to decide
whether to dump the hw data or not. That way, the callers can make the decision,
leaving the disable_hw code unaware of the mode checks.

Suzuki