drm/i915/selftests: Use mul_u32_u32() for 32b x 32b -> 64b result

As realised by commit 9e3d622 ("math64, timers: Fix 32bit mul_u64_u32_shr() and friends"), GCC does not always generate ideal code for performing a 32b x 32b multiply returning a 64b result (i.e. where we idiomatically use u64 result = (u64)x * (u32)x). Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Link: https://patchwork.freedesktop.org/patch/msgid/20170913105154.2910-2-chris@chris-wilson.co.uk Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
mariux64 · Sep 13, 2017 · 7ce5b68 · 7ce5b68
1 parent 3123698
commit 7ce5b68
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Showing 3 changed files with 6 additions and 6 deletions.
diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_timeline.c b/drivers/gpu/drm/i915/selftests/i915_gem_timeline.c
@@ -121,7 +121,7 @@ static int igt_sync(void *arg)
 
 static unsigned int random_engine(struct rnd_state *rnd)
 {
-	return ((u64)prandom_u32_state(rnd) * I915_NUM_ENGINES) >> 32;
+	return i915_prandom_u32_max_state(I915_NUM_ENGINES, rnd);
 }
 
 static int bench_sync(void *arg)

diff --git a/drivers/gpu/drm/i915/selftests/i915_random.c b/drivers/gpu/drm/i915/selftests/i915_random.c
@@ -41,11 +41,6 @@ u64 i915_prandom_u64_state(struct rnd_state *rnd)
 	return x;
 }
 
-static inline u32 i915_prandom_u32_max_state(u32 ep_ro, struct rnd_state *state)
-{
-	return upper_32_bits((u64)prandom_u32_state(state) * ep_ro);
-}
-
 void i915_random_reorder(unsigned int *order, unsigned int count,
 			 struct rnd_state *state)
 {

diff --git a/drivers/gpu/drm/i915/selftests/i915_random.h b/drivers/gpu/drm/i915/selftests/i915_random.h
@@ -43,6 +43,11 @@
 
 u64 i915_prandom_u64_state(struct rnd_state *rnd);
 
+static inline u32 i915_prandom_u32_max_state(u32 ep_ro, struct rnd_state *state)
+{
+	return upper_32_bits(mul_u32_u32(prandom_u32_state(state), ep_ro));
+}
+
 unsigned int *i915_random_order(unsigned int count,
 				struct rnd_state *state);
 void i915_random_reorder(unsigned int *order,