Re: [PATCH igt 2/2] igt/perf_pmu: 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=103929
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>   tests/perf_pmu.c | 16 +++++++++++++++-
>   1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/tests/perf_pmu.c b/tests/perf_pmu.c
> index e872f4e55..65bc734da 100644
> --- a/tests/perf_pmu.c
> +++ b/tests/perf_pmu.c
> @@ -1008,6 +1008,20 @@ static unsigned long rc6_enable_us(void)
>   	return 2 * 160 * 1000;
>   }
>   
> +static bool wait_for_rc6(int fd)
> +{
> +	struct timespec tv = {};
> +	uint64_t start, now;
> +
> +	start = pmu_read_single(fd);
> +	do {
> +		usleep(50);

Not needlessly fast?

> +		now = pmu_read_single(fd);
> +	} while (start == now && !igt_seconds_elapsed(&tv));

So up to one second wait.

> +
> +	return start != now;
> +}
> +
>   static void
>   test_rc6(int gem_fd)
>   {
> @@ -1019,7 +1033,7 @@ test_rc6(int gem_fd)
>   	fd = open_pmu(I915_PMU_RC6_RESIDENCY);
>   
>   	gem_quiescent_gpu(gem_fd);
> -	usleep(rc6_enable_us()); /* wait for the rc6 cycle counter to kick in */
> +	igt_require(wait_for_rc6(fd));

Eliminate now unused rc6_enable_us() ?

>   
>   	/* Go idle and check full RC6. */
>   	prev = pmu_read_single(fd);
> 

With dead-code removed:

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

Regards,

Tvrtko
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