arm64: cpufeature: Use pmuv3_implemented() function

Other places that are doing this version comparison are already using
pmuv3_implemented(), so might as well use it here too for consistency.

Signed-off-by: James Clark <james.clark@linaro.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Colton Lewis <coltonlewis@google.com>
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/arch/arm/include/asm/arm_pmuv3.h b/arch/arm/include/asm/arm_pmuv3.h
index 2ec0e5e83fc9..ecfede0c0348 100644
--- a/arch/arm/include/asm/arm_pmuv3.h
+++ b/arch/arm/include/asm/arm_pmuv3.h
@@ -238,6 +238,13 @@ static inline void kvm_vcpu_pmu_resync_el0(void) {}
 
 static inline bool pmuv3_implemented(int pmuver)
 {
+	/*
+	 * PMUVer follows the standard ID scheme for an unsigned field with the
+	 * exception of 0xF (IMP_DEF) which is treated specially and implies
+	 * FEAT_PMUv3 is not implemented.
+	 *
+	 * See DDI0487L.a D24.1.3.2 for more details.
+	 */
 	return !(pmuver == ARMV8_PMU_DFR_VER_IMP_DEF ||
 		 pmuver == ARMV8_PMU_DFR_VER_NI);
 }