From nobody Fri Dec 19 04:15:30 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F13E2CDB474 for ; Fri, 13 Oct 2023 02:44:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229509AbjJMCo2 (ORCPT ); Thu, 12 Oct 2023 22:44:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229436AbjJMCo1 (ORCPT ); Thu, 12 Oct 2023 22:44:27 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 18E8083 for ; Thu, 12 Oct 2023 19:44:25 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 267A611FB; Thu, 12 Oct 2023 19:45:05 -0700 (PDT) Received: from a077893.blr.arm.com (a077893.blr.arm.com [10.162.41.8]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 52BE93F7A6; Thu, 12 Oct 2023 19:44:22 -0700 (PDT) From: Anshuman Khandual To: linux-arm-kernel@lists.infradead.org Cc: Anshuman Khandual , Will Deacon , Mark Rutland , linux-kernel@vger.kernel.org, James Clark Subject: [PATCH V2] drivers: perf: arm_pmuv3: Read PMMIR_EL1 unconditionally Date: Fri, 13 Oct 2023 08:13:54 +0530 Message-Id: <20231013024354.1289070-1-anshuman.khandual@arm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 --- 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.c= om/ 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 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); =20 /* store PMMIR register for sysfs */ - if (is_pmuv3p4(pmuver) && (pmceid_raw[1] & BIT(31))) + if (is_pmuv3p4(pmuver)) cpu_pmu->reg_pmmir =3D read_pmmir(); else cpu_pmu->reg_pmmir =3D 0; --=20 2.25.1