From 58f8fc57b1d314b5402c374a8c454ac7c870574c Mon Sep 17 00:00:00 2001 From: Anshuman Khandual Date: Fri, 13 Oct 2023 08:13:54 +0530 Subject: [PATCH] drivers: perf: arm_pmuv3: Read PMMIR_EL1 unconditionally 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 Cc: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Reviewed-by: James Clark Signed-off-by: Anshuman Khandual Link: https://lore.kernel.org/r/20231013024354.1289070-1-anshuman.khandual@arm.com Signed-off-by: Will Deacon --- drivers/perf/arm_pmuv3.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c index 8fcaa26f0f8a6..4ee0afe005271 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; -- 2.30.2