| Message ID | 20231013024354.1289070-1-anshuman.khandual@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [V2] drivers: perf: arm_pmuv3: Read PMMIR_EL1 unconditionally | expand |
On Fri, 13 Oct 2023 08:13:54 +0530, Anshuman Khandual wrote: > Currently the PMUv3 driver only reads PMMIR_EL1 if the PMU implements > FEAT_PMUv3p4 and the STALL_SLOT event, but the check for STALL_SLOT event > isn't necessary and can be removed. > > The check for STALL_SLOT event was introduced with the read of PMMIR_EL1 in > commit f5be3a61fdb5dd11 ("arm64: perf: Add support caps under sysfs") > > [...] Applied to will (for-next/perf), thanks! [1/1] drivers: perf: arm_pmuv3: Read PMMIR_EL1 unconditionally https://git.kernel.org/will/c/58f8fc57b1d3 Cheers,
diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c index 144593092727..92fefc1bc7f6 100644 --- a/drivers/perf/arm_pmuv3.c +++ b/drivers/perf/arm_pmuv3.c @@ -1126,7 +1126,7 @@ static void __armv8pmu_probe_pmu(void *info) pmceid, ARMV8_PMUV3_MAX_COMMON_EVENTS); /* store PMMIR register for sysfs */ - if (is_pmuv3p4(pmuver) && (pmceid_raw[1] & BIT(31))) + if (is_pmuv3p4(pmuver)) cpu_pmu->reg_pmmir = read_pmmir(); else cpu_pmu->reg_pmmir = 0;
Currently the PMUv3 driver only reads PMMIR_EL1 if the PMU implements FEAT_PMUv3p4 and the STALL_SLOT event, but the check for STALL_SLOT event isn't necessary and can be removed. The check for STALL_SLOT event was introduced with the read of PMMIR_EL1 in commit f5be3a61fdb5dd11 ("arm64: perf: Add support caps under sysfs") When this logic was written, the ARM ARM said: | If STALL_SLOT is not implemented, it is IMPLEMENTATION DEFINED whether | the PMMIR System registers are implemented. ... and thus the driver had to check for STALL_SLOT event to verify that PMMIR_EL1 was implemented and accesses to PMMIR_EL1 would not be UNDEFINED. Subsequently, the architecture was retrospectively tightened to require that any FEAT_PMUv3p4 implementation implements PMMIR_EL1. Since the G.b release of the ARM ARM, the wording regarding STALL_SLOT event has been removed, and the description of PMMIR_EL1 says: | This register is present only when FEAT_PMUv3p4 is implemented. Drop the unnecessary check for STALL_SLOT event when reading PMMIR_EL1. Cc: Will Deacon <will@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Reviewed-by: James Clark <james.clark@arm.com> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> --- This applies on v6.6-rc5 Changes in V2: - Updated commit message to include previous context about STALL_SLOT check Changes in V1: https://lore.kernel.org/all/20231009075631.193208-1-anshuman.khandual@arm.com/ drivers/perf/arm_pmuv3.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)