linux-kernel - Re: [PATCH v2 24/27] coresight: tmc-etr: Relax collection of trace from sysfs mode

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Date:   Mon, 7 May 2018 16:54:42 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mike.leach@...aro.org, robert.walker@....com, mark.rutland@....com,
        will.deacon@....com, robin.murphy@....com, sudeep.holla@....com,
        frowand.list@...il.com, robh@...nel.org, john.horley@....com
Subject: Re: [PATCH v2 24/27] coresight: tmc-etr: Relax collection of trace
 from sysfs mode

On Tue, May 01, 2018 at 10:10:54AM +0100, Suzuki K Poulose wrote:
> Since the ETR now uses mode specific buffers, we can reliably
> provide the trace data captured in sysfs mode, even when the ETR
> is operating in PERF mode.
> 
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  drivers/hwtracing/coresight/coresight-tmc-etr.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index a35a12f..7551272 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -1439,19 +1439,17 @@ int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
>  		goto out;
>  	}
>  
> -	/* Don't interfere if operated from Perf */
> -	if (drvdata->mode == CS_MODE_PERF) {
> -		ret = -EINVAL;
> -		goto out;
> -	}
> -
> -	/* If sysfs_buf is NULL the trace data has been read already */
> +	/*
> +	 * We can safely allow reads even if the ETR is operating in PERF mode,
> +	 * since the sysfs session is captured in mode specific data.
> +	 * If drvdata::sysfs_data is NULL the trace data has been read already.
> +	 */
>  	if (!drvdata->sysfs_buf) {
>  		ret = -EINVAL;
>  		goto out;
>  	}
>  
> -	/* Disable the TMC if we are trying to read from a running session */
> +	/* Disable the TMC if we are trying to read from a running session. */

Move that to the previous patch.

>  	if (drvdata->mode == CS_MODE_SYSFS)
>  		tmc_etr_disable_hw(drvdata);
>  
> -- 
> 2.7.4
>