PMU reads the GT timestamp as a 2x32 mmio read and since upper and lower 32 bit registers are read in a loop, there is a latency involved between getting the GT timestamp and the CPU timestamp. As part of the resolution, refactor intel_uncore_read64_2x32 to acquire forcewake and uncore lock prior to reading upper and lower regs.
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.rama...@intel.com> --- drivers/gpu/drm/i915/intel_uncore.h | 44 ++++++++++++++++++++--------- 1 file changed, 30 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_uncore.h b/drivers/gpu/drm/i915/intel_uncore.h index 5449146a0624..e9e38490815d 100644 --- a/drivers/gpu/drm/i915/intel_uncore.h +++ b/drivers/gpu/drm/i915/intel_uncore.h @@ -382,20 +382,6 @@ __uncore_write(write_notrace, 32, l, false) */ __uncore_read(read64, 64, q, true) -static inline u64 -intel_uncore_read64_2x32(struct intel_uncore *uncore, - i915_reg_t lower_reg, i915_reg_t upper_reg) -{ - u32 upper, lower, old_upper, loop = 0; - upper = intel_uncore_read(uncore, upper_reg); - do { - old_upper = upper; - lower = intel_uncore_read(uncore, lower_reg); - upper = intel_uncore_read(uncore, upper_reg); - } while (upper != old_upper && loop++ < 2); - return (u64)upper << 32 | lower; -} - #define intel_uncore_posting_read(...) ((void)intel_uncore_read_notrace(__VA_ARGS__)) #define intel_uncore_posting_read16(...) ((void)intel_uncore_read16_notrace(__VA_ARGS__)) @@ -455,6 +441,36 @@ static inline void intel_uncore_rmw_fw(struct intel_uncore *uncore, intel_uncore_write_fw(uncore, reg, val); } +static inline u64 +intel_uncore_read64_2x32(struct intel_uncore *uncore, + i915_reg_t lower_reg, i915_reg_t upper_reg) +{ + u32 upper, lower, old_upper, loop = 0; + enum forcewake_domains fw_domains; + unsigned long flags; + + fw_domains = intel_uncore_forcewake_for_reg(uncore, lower_reg, + FW_REG_READ); + + fw_domains |= intel_uncore_forcewake_for_reg(uncore, upper_reg, + FW_REG_READ); + + spin_lock_irqsave(&uncore->lock, flags); + intel_uncore_forcewake_get__locked(uncore, fw_domains); + + upper = intel_uncore_read_fw(uncore, upper_reg); + do { + old_upper = upper; + lower = intel_uncore_read_fw(uncore, lower_reg); + upper = intel_uncore_read_fw(uncore, upper_reg); + } while (upper != old_upper && loop++ < 2); + + intel_uncore_forcewake_put__locked(uncore, fw_domains); + spin_unlock_irqrestore(&uncore->lock, flags); + + return (u64)upper << 32 | lower; +} + static inline int intel_uncore_write_and_verify(struct intel_uncore *uncore, i915_reg_t reg, u32 val, u32 mask, u32 expected_val) -- 2.36.1