Commit 0331365e authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon

arm64: perf: correct PMUVer probing

The ID_AA64DFR0_EL1.PMUVer field doesn't follow the usual ID registers
scheme. While value 0xf indicates a non-architected PMU is implemented,
values 0x1 to 0xe indicate an increasingly featureful architected PMU,
as if the field were unsigned.

For more details, see ARM DDI 0487C.a, D10.1.4, "Alternative ID scheme
used for the Performance Monitors Extension version".

Currently, we treat the field as signed, and erroneously bail out for
values 0x8 to 0xe. Let's correct that.
Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarRobin Murphy <robin.murphy@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 167e6143
......@@ -908,9 +908,9 @@ static void __armv8pmu_probe_pmu(void *info)
int pmuver;
dfr0 = read_sysreg(id_aa64dfr0_el1);
pmuver = cpuid_feature_extract_signed_field(dfr0,
pmuver = cpuid_feature_extract_unsigned_field(dfr0,
ID_AA64DFR0_PMUVER_SHIFT);
if (pmuver < 1)
if (pmuver == 0xf || pmuver == 0)
return;
probe->present = true;
......
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