[Intel-gfx] [PATCH] drm/i915: Fixup 64bit divides in timelines selftest

[Tvrtko Ursulin]

On 13/05/2017 10:41, Chris Wilson wrote:
> Some 64b divides snuck in when doing the prng timing compensation.
>
> Fixes: 4797948071f6 ("drm/i915: Squash repeated awaits on the same fence")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/selftests/i915_gem_timeline.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_timeline.c b/drivers/gpu/drm/i915/selftests/i915_gem_timeline.c
> index 6df00cc02c12..7a44dab631b8 100644
> --- a/drivers/gpu/drm/i915/selftests/i915_gem_timeline.c
> +++ b/drivers/gpu/drm/i915/selftests/i915_gem_timeline.c
> @@ -126,7 +126,6 @@ static unsigned int random_engine(struct rnd_state *rnd)
>
>  static int bench_sync(void *arg)
>  {
> -#define M (1 << 20)
>  	struct rnd_state prng;
>  	struct intel_timeline *tl;
>  	unsigned long end_time, count;
> @@ -158,7 +157,7 @@ static int bench_sync(void *arg)
>  	kt = ktime_sub(ktime_get(), kt);
>  	pr_debug("%s: %lu random evaluations, %lluns/prng\n",
>  		 __func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
> -	prng32_1M = ktime_to_ns(kt) * M / count;
> +	prng32_1M = div64_ul(ktime_to_ns(kt) << 20, count);
>
>  	/* Benchmark (only) setting random context ids */
>  	prandom_seed_state(&prng, i915_selftest.random_seed);
> @@ -172,7 +171,7 @@ static int bench_sync(void *arg)
>  		count++;
>  	} while (!time_after(jiffies, end_time));
>  	kt = ktime_sub(ktime_get(), kt);
> -	kt = ktime_sub_ns(kt, count * prng32_1M * 2 / M);
> +	kt = ktime_sub_ns(kt, (count * prng32_1M * 2) >> 20);
>  	pr_info("%s: %lu random insertions, %lluns/insert\n",
>  		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
>
> @@ -190,7 +189,7 @@ static int bench_sync(void *arg)
>  		}
>  	}
>  	kt = ktime_sub(ktime_get(), kt);
> -	kt = ktime_sub_ns(kt, count * prng32_1M * 2 / M);
> +	kt = ktime_sub_ns(kt, (count * prng32_1M * 2) >> 20);
>  	pr_info("%s: %lu random lookups, %lluns/lookup\n",
>  		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
>
> @@ -248,7 +247,7 @@ static int bench_sync(void *arg)
>  		count++;
>  	} while (!time_after(jiffies, end_time));
>  	kt = ktime_sub(ktime_get(), kt);
> -	kt = ktime_sub_ns(kt, count * prng32_1M * 2 / M);
> +	kt = ktime_sub_ns(kt, (count * prng32_1M * 2) >> 20);
>  	pr_info("%s: %lu repeated insert/lookups, %lluns/op\n",
>  		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
>  	mock_timeline_destroy(tl);
> @@ -287,7 +286,6 @@ static int bench_sync(void *arg)
>  	}
>
>  	return 0;
> -#undef M
>  }
>
>  int i915_gem_timeline_mock_selftests(void)
>

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

Regards,

Tvrtko