As realised by commit 9e3d6223d209 ("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@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/selftests/i915_gem_timeline.c | 2 +-
drivers/gpu/drm/i915/selftests/i915_random.c | 5 -----
drivers/gpu/drm/i915/selftests/i915_random.h | 5 +++++
3 files changed, 6 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 7a44dab631b8..4795877abe56 100644
--- 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
index d044bf9a6feb..ea0f5dbc0eb7 100644
--- 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
index 6c9379871384..7dffedc501ca 100644
--- 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,
--
2.13.3
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