drm/i915: Use mul_u32_u32() for 32b x 32b -> 64b result
authorChris Wilson <chris@chris-wilson.co.uk>
Wed, 13 Sep 2017 10:51:53 +0000 (11:51 +0100)
committerChris Wilson <chris@chris-wilson.co.uk>
Wed, 13 Sep 2017 12:27:20 +0000 (13:27 +0100)
commit3123698f50fe4ac9ddb775dcd2b34a1d9cdd603f
tree19bf0a89fe2f609d5bb4a8cdbfb00c20ed280502
parente60b36f76c2ee0ba90b431daa534bc262798fb26
drm/i915: Use mul_u32_u32() for 32b x 32b -> 64b result

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). This catches a
couple of instances in the display code using (u64)x * (u32)y.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20170913105154.2910-1-chris@chris-wilson.co.uk
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
drivers/gpu/drm/i915/intel_display.c
drivers/gpu/drm/i915/intel_tv.c