From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 44509538D6D for ; Tue, 8 Sep 2026 12:28:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788870525; cv=none; b=jJUXdpRxoKfiCNWshZA7hjqOHDMBp/B8la+hQFJzdO+WzLwtf7YStLkBoAR2vD0KIQIJ+gm7PRZDbdFGRTrYjv9pBpPyxqwo8DCisBemPfuSFtMcKRM5HV/1bVs5V3HFL5/Idli8ES5qfu0hTJmxZ8Lxl23Ui/zcWM3EYfy9Qlg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788870525; c=relaxed/simple; bh=XZvB0Pq2aNkp+7CMzCyqKeCftuhCL7mGCNUrTypyU0Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ctjc8sfMekcfDi2nTrVHe+JYOEsGXDj2OJSY2M9maF4Gjx77JhM+ldJU+fcMT/vR0hdlbPsr5Viw9+W2wfmE7GYsOxfG7D/0we3OhnGd9IAtL+1vzeiGuBTZP75XsBKD0FPRwURUwxC4frya/nZGPCukuTluWBCgOUnFJM0wSA4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1A141F00A3D; Tue, 8 Sep 2026 12:28:43 +0000 (UTC) From: Sasha Levin To: stable@vger.kernel.org Cc: Christian Loehle , Sumit Gupta , "Rafael J. Wysocki" , Sasha Levin Subject: [PATCH 6.6.y] ACPI: CPPC: Reject desired_perf reads on _CPC revision 4+ Date: Tue, 8 Sep 2026 08:28:40 -0400 Message-ID: <20260908122840.2091786-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090308-padlock-setting-e1ac@gregkh> References: <2026090308-padlock-setting-e1ac@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Christian Loehle [ Upstream commit df5a1d4a8cdfda20eb2581a85e81c7d436866534 ] When CPPC feedback counters cannot provide a usable sample, cppc-cpufreq calls cppc_get_desired_perf() because some platforms repurpose Desired Performance to report actual delivered performance. ACPI 6.5 defines _CPC revision 3 and lists Read/Write as the Optional Attribute of Desired Performance. ACPI 6.6 advances _CPC to revision 4 and lists only Write, so invoking that workaround for revision 4 or later would require a register read that the interface no longer specifies. Make cppc_get_desired_perf() return -EOPNOTSUPP for _CPC revision 4 or later. Use the revision retained in the per-CPU CPC descriptor rather than the platform-wide FADT revision. The _CPC revision may still not accurately describe the implemented register semantics. If a nominally revision 3 platform implements a non-readable Desired Performance register, a read may return zero and make cppc_cpufreq_get_rate() report 0 kHz. Treat a zero read as unusable and fall back to the cached OSPM request, just as for a failed read. Fixes: c47195631960 ("cppc_cpufreq: Use desired perf if feedback ctrs are 0 or unchanged") Cc: stable@vger.kernel.org Suggested-by: Sumit Gupta Signed-off-by: Christian Loehle Link: https://patch.msgid.link/20260803203531.1268651-2-christian.loehle@arm.com Signed-off-by: Rafael J. Wysocki [ preserved the original CPPC revision while parsing only the supported v3 prefix and retaining cppc_get_perf() ] Signed-off-by: Sasha Levin --- drivers/acpi/cppc_acpi.c | 13 +++++++++++-- drivers/cpufreq/cppc_cpufreq.c | 2 +- 2 files changed, 12 insertions(+), 3 deletions(-) diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 33b3e6dd17c58..c9ae5ea408a04 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -764,7 +764,6 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr) } if (cpc_rev > CPPC_V3_REV) { num_ent = CPPC_V3_NUM_ENT; - cpc_rev = CPPC_V3_REV; } cpc_ptr->num_entries = num_ent; @@ -1222,10 +1221,20 @@ static int cppc_get_perf(int cpunum, enum cppc_regs reg_idx, u64 *perf) * @cpunum: CPU from which to get desired performance. * @desired_perf: Return address. * - * Return: 0 for success, -EIO otherwise. + * Return: 0 for success, -EOPNOTSUPP for _CPC revision 4 or later, and a + * negative errno otherwise. */ int cppc_get_desired_perf(int cpunum, u64 *desired_perf) { + struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpunum); + + if (!cpc_desc) + return -ENODEV; + + /* _CPC revision 4 no longer specifies Desired Performance as readable. */ + if (cpc_desc->version > CPPC_V3_REV) + return -EOPNOTSUPP; + return cppc_get_perf(cpunum, DESIRED_PERF, desired_perf); } EXPORT_SYMBOL_GPL(cppc_get_desired_perf); diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c index 4d96eed64fe0c..5a5832a2f9b2a 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -813,7 +813,7 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpu) * value first as some platforms may update the actual delivered perf * there; if failed, resort to the cached desired perf. */ - if (cppc_get_desired_perf(cpu, &delivered_perf)) + if (cppc_get_desired_perf(cpu, &delivered_perf) || !delivered_perf) delivered_perf = cpu_data->perf_ctrls.desired_perf; return cppc_perf_to_khz(&cpu_data->perf_caps, delivered_perf); -- 2.53.0