6.12-stable review patch. If anyone has any objections, please let me know.
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From: Umesh Nerlige Ramappa umesh.nerlige.ramappa@intel.com
[ Upstream commit 7d44ad6b43d0be43d080180413a1b6c24cfbd266 ]
When tick values are large, the multiplication by NSEC_PER_SEC is larger than 64 bits and results in bad conversions.
The issue is seen in PMU busyness counters that look like they have wrapped around due to bad conversion. i915 PMU implementation returns monotonically increasing counters. If a count is lesser than previous one, it will only return the larger value until the smaller value catches up. The user will see this as zero delta between two measurements even though the engines are busy.
Fix it by using mul_u64_u32_div()
Fixes: 77cdd054dd2c ("drm/i915/pmu: Connect engine busyness stats from GuC to pmu") Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14955 Signed-off-by: Umesh Nerlige Ramappa umesh.nerlige.ramappa@intel.com Reviewed-by: Ashutosh Dixit ashutosh.dixit@intel.com Link: https://lore.kernel.org/r/20251016000350.1152382-2-umesh.nerlige.ramappa@int... (cherry picked from commit 2ada9cb1df3f5405a01d013b708b1b0914efccfe) Signed-off-by: Rodrigo Vivi rodrigo.vivi@intel.com [Rodrigo: Added the Fixes tag while cherry-picking to fixes] Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/i915/gt/intel_gt_clock_utils.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_clock_utils.c b/drivers/gpu/drm/i915/gt/intel_gt_clock_utils.c index 6e63505fe4781..f01399c78c99d 100644 --- a/drivers/gpu/drm/i915/gt/intel_gt_clock_utils.c +++ b/drivers/gpu/drm/i915/gt/intel_gt_clock_utils.c @@ -209,7 +209,7 @@ static u64 div_u64_roundup(u64 nom, u32 den)
u64 intel_gt_clock_interval_to_ns(const struct intel_gt *gt, u64 count) { - return div_u64_roundup(count * NSEC_PER_SEC, gt->clock_frequency); + return mul_u64_u32_div(count, NSEC_PER_SEC, gt->clock_frequency); }
u64 intel_gt_pm_interval_to_ns(const struct intel_gt *gt, u64 count) @@ -219,7 +219,7 @@ u64 intel_gt_pm_interval_to_ns(const struct intel_gt *gt, u64 count)
u64 intel_gt_ns_to_clock_interval(const struct intel_gt *gt, u64 ns) { - return div_u64_roundup(gt->clock_frequency * ns, NSEC_PER_SEC); + return mul_u64_u32_div(ns, gt->clock_frequency, NSEC_PER_SEC); }
u64 intel_gt_ns_to_pm_interval(const struct intel_gt *gt, u64 ns)