Re: [PATCH 3/3] coresight: etm3x: Release CLAIM tag when operated from perf

[leo . yan]

Hi Mathieu,

On Mon, Nov 05, 2018 at 03:26:30PM -0700, Mathieu Poirier wrote:
> This patch deals with the release of the CLAIM tag when the ETM is
> operated from perf.  Otherwise the tag is left asserted and subsequent
> requests to use the device fail.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> ---
>  drivers/hwtracing/coresight/coresight-etm3x.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
> index fd5c4cca7db5..000796394662 100644
> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
> @@ -603,6 +603,8 @@ static void etm_disable_perf(struct coresight_device *csdev)
>  	 */
>  	etm_set_pwrdwn(drvdata);
>  
> +	coresight_disclaim_device_unlocked(drvdata->base);
> +

Just remind, this isn't consistent with the sequency in function
etm_disable_hw(), which has the reversed sequence between
etm_set_pwrdwn() and coresight_disclaim_device_unlocked().

Not sure which one sequence is more suitable, at the first glance,
accessing register after pwrdwn related operation might have risk for
deadlock?

Thanks,
Leo Yan

>  	CS_LOCK(drvdata->base);
>  }
>  
> -- 
> 2.7.4
>