From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 4188A411F82; Wed, 29 Jul 2026 10:03:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785319385; cv=none; b=tMvJzviXCuZDHplPUySk7W7OBqXoR4zCxwzRVgb0r0PdcmeFoqmVSzVKv1dHX1ApUXcBbTENUjlbNQj0ezgZym2Ihber2j7dXH82ulpA54YKTdD7AN/KwsHsA/a5iZane4l8Ovl5Sxb958g4khvIC/ENmug17ckJ2Og12D4kgVs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785319385; c=relaxed/simple; bh=MarEHk2652I/6KoWbb1IPd7ch3p/VBSZ1ZmAfKZ5Jcc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=NC0YLHqtD5/QPSO15g6yCtkvQqXAxRC1Y2xdKvOQ/otPHEgFvG3ShJjh2CikozATVif/kxcfedhAvGEgbjMSzfpajjshaYTR3LSgxpE8Wt56JJ3svYgSg2a812G+AoZY39GByOaMeWsCgDBAEg37NArHaXutsJDE1hraFEz/Qa4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=PBCKqK5c; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="PBCKqK5c" 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 6A43915A1; Wed, 29 Jul 2026 03:02:58 -0700 (PDT) Received: from e127648.cambridge.arm.com (e127648.arm.com [10.1.39.91]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id C15103F86F; Wed, 29 Jul 2026 03:02:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785319382; bh=MarEHk2652I/6KoWbb1IPd7ch3p/VBSZ1ZmAfKZ5Jcc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PBCKqK5crlCmmhSNVY38suluveZb5gLr5BgYpAt9LUlHSQTfBMjO3vHfGiD7+4JCG HVaOYeaUvnGZ8qlfFt4ti2YxAwIDFndqsNDIiIKye2Kb9D4PRs7rpjUHjBCKHqQDTD phT5Q0TxDFRLYDs781U0CXTkCrn9CQVRbcGVV6Mw= From: Christian Loehle To: "Rafael J . Wysocki" , Viresh Kumar Cc: linux-pm@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, Len Brown , Jie Zhan , Lifeng Zheng , Pierre Gondois , Sumit Gupta , Sudeep Holla , Ionela Voinescu , zhongqiu.han@oss.qualcomm.com, Christian Loehle , stable@vger.kernel.org Subject: [PATCHv2 2/3] ACPI: CPPC: Skip desired_perf read in cppc_get_perf() Date: Wed, 29 Jul 2026 11:02:44 +0100 Message-Id: <20260729100245.2628302-3-christian.loehle@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260729100245.2628302-1-christian.loehle@arm.com> References: <20260729100245.2628302-1-christian.loehle@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ACPI 6.6 changed the Optional Attribute of Desired Performance from Read/Write to Write. cppc_get_perf() nevertheless reads the register when initializing performance controls, even though cppc-cpufreq overwrites the value before using it. Use the readability check from cppc_get_desired_perf() and leave desired_perf zero instead of reading it on ACPI 6.6 or later. Also exclude the register from PCC read-command detection so it cannot trigger an otherwise unnecessary read command. Fixes: 658fa7b1c47a ("ACPI: CPPC: Add cppc_get_perf() API to read performance controls") Cc: stable@vger.kernel.org Suggested-by: Zhongqiu Han Signed-off-by: Christian Loehle --- drivers/acpi/cppc_acpi.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 6e5381f8de38..210988d57b71 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -1843,6 +1843,7 @@ int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) u64 desired_perf = 0, min = 0, max = 0, energy_perf = 0, auto_sel = 0; int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu); struct cppc_pcc_data *pcc_ss_data = NULL; + bool read_desired_perf = cppc_desired_perf_readable(); int ret = 0, regs_in_pcc = 0; if (!cpc_desc) { @@ -1862,7 +1863,8 @@ int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) auto_sel_reg = &cpc_desc->cpc_regs[AUTO_SEL_ENABLE]; /* Are any of the regs PCC ?*/ - if (CPC_IN_PCC(desired_perf_reg) || CPC_IN_PCC(min_perf_reg) || + if ((read_desired_perf && CPC_IN_PCC(desired_perf_reg)) || + CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg) || CPC_IN_PCC(energy_perf_reg) || CPC_IN_PCC(auto_sel_reg)) { if (pcc_ss_id < 0) { @@ -1894,7 +1896,7 @@ int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) } perf_ctrls->min_perf = min; - if (CPC_SUPPORTED(desired_perf_reg)) { + if (read_desired_perf && CPC_SUPPORTED(desired_perf_reg)) { ret = cpc_read(cpu, desired_perf_reg, &desired_perf); if (ret) goto out_err; -- 2.34.1