Re: [PATCH igt 1/2] igt/pm_rc6_residency: Replace hard-coded sleep before rc6 with a probe

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 05/12/2017 10:56, Chris Wilson wrote:
> Instead of trying to sleep for 2 evaluations intervals and then assuming
> that rc6 is working, poll the rc6 residency instead.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=104099
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>   tests/pm_rc6_residency.c | 33 ++++++++++++++-------------------
>   1 file changed, 14 insertions(+), 19 deletions(-)
> 
> diff --git a/tests/pm_rc6_residency.c b/tests/pm_rc6_residency.c
> index 3f6860199..16f4b1421 100644
> --- a/tests/pm_rc6_residency.c
> +++ b/tests/pm_rc6_residency.c
> @@ -122,9 +122,6 @@ static void measure_residencies(int devid, unsigned int mask,
>   	struct residencies end = { };
>   	int retry;
>   
> -	if (!mask)
> -		return;
> -
>   	/*
>   	 * Retry in case of counter wrap-around. We simply re-run the
>   	 * measurement, since the valid counter range is different on
> @@ -168,17 +165,18 @@ static void measure_residencies(int devid, unsigned int mask,
>   	res->rc6 += res->rc6p;
>   }
>   
> -static unsigned long rc6_enable_us(void)
> +static bool wait_for_rc6(void)
>   {
> -	/*
> -	 * To know how long we need to wait for the device to enter rc6 once
> -	 * idle, we need to look at GEN6_RC_EVALUATION_INTERVAL. Currently,
> -	 * this is set to 125000 (12500 * 1280ns or 0.16s) on all platforms.
> -	 * We must complete at least one EI with activity below the
> -	 * per-platform threshold for RC6 to kick. Therefore, we must wait
> -	 * at least 2 EI cycles, before we can expect rc6 to start ticking.
> -	 */
> -	return 2 * 160 * 1000;
> +	struct timespec tv = {};
> +	unsigned long start, now;
> +
> +	start = read_rc6_residency("rc6");
> +	do {
> +		usleep(50);
> +		now = read_rc6_residency("rc6");
> +	} while (now == start && !igt_seconds_elapsed(&tv));
> +
> +	return now != start;
>   }
>   
>   igt_main
> @@ -198,19 +196,17 @@ igt_main
>   
>   		/* Make sure rc6 counters are running */
>   		igt_drop_caches_set(fd, DROP_IDLE);
> -		usleep(rc6_enable_us());
> +		igt_require(wait_for_rc6());
>   
>   		close(fd);
>   
>   		rc6_enabled = get_rc6_enabled_mask();
> -		igt_require(rc6_enabled);
> +		igt_require(rc6_enabled & RC6_ENABLED);
>   	}
>   
>   	igt_subtest("rc6-accuracy") {
>   		struct residencies res;
>   
> -		igt_require(rc6_enabled & RC6_ENABLED);
> -
>   		measure_residencies(devid, rc6_enabled, &res);
>   		residency_accuracy(res.rc6, res.duration, "rc6");
>   	}
> @@ -218,8 +214,7 @@ igt_main
>   	igt_subtest("media-rc6-accuracy") {
>   		struct residencies res;
>   
> -		igt_require((rc6_enabled & RC6_ENABLED) &&
> -			    (IS_VALLEYVIEW(devid) || IS_CHERRYVIEW(devid)));
> +		igt_require(IS_VALLEYVIEW(devid) || IS_CHERRYVIEW(devid));
>   
>   		measure_residencies(devid, rc6_enabled, &res);
>   		residency_accuracy(res.media_rc6, res.duration, "media_rc6");
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
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