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 855D91DDFE for ; Tue, 8 Sep 2026 01:38:47 +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=1788831528; cv=none; b=kgZKlQhAQOTndzzEzBYO5/n+UvojmLjhy10df1uVK2JCBy/Wlp83Kxl3n3G2EeuZfufsVex41EE4mPmjQv84p5OAdbmIK+NY+BSsZY/KB61g8j8EyR3Oh4lPYkbq7KIQyw7tTcDxxfeqZkfgMV05qxSLyIzxja36bht+1m6fhj4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788831528; c=relaxed/simple; bh=qk1O0RApGco72entdCdBPQgFOKmDjK0QINsjkTSkZjo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aIw73QxGZRyVTTknPFuHjdASWAHGSBZzC0pMUI/H/q4O3loweMdAOcTkf81zh00v5WhzihnGER1NnaDzdocMTxPDPHE6B+ohOhoG7APGGAby4iacg0jDpawv2moHrN4woMlqp430SI+rg5fvMp3mcpCzIIc/TVe80zHgKNDcYbc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ExkJk/hu; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ExkJk/hu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 913AB1F00A3A; Tue, 8 Sep 2026 01:38:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788831527; bh=4DR/BR85M4a3jtJ7A8aBy3ii6k2D/fLbCqGYB/iGZ6s=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ExkJk/huwDQ7scxSqSFn2VWV8n2gGhufG4iPdPnOEvO1DgoR2D2USM26HlvrkWiDb a0xBEzC27Bypmo7kE20yfK7K7ZUqJYEon+rC7EsbqhbiqpTlvgw62uibc3LmV6SrCb sBHVCJ+jDZanfUjbSt3oHAYgTwXLUB5pa+jrpDApSlEiSeiS9qyGtMeYVBx1brbH3d 40uhBSzoeBnPmLxRATLUFH0TQW13ejqKPF3IfpYbaSYSBrc7F7FO3ZClvyxpF+d2Gz OlZ6TQFmqqsHBlZ401Bf4zDgSJI+1+NKMSXWbEdF/htFFYEhtHgnmyy82g/EhWDY13 JITf+RdnxKftA== From: Sasha Levin To: stable@vger.kernel.org Cc: Christian Loehle , Sumit Gupta , "Rafael J. Wysocki" , Sasha Levin Subject: [PATCH 6.18.y] ACPI: CPPC: Reject desired_perf reads on _CPC revision 4+ Date: Mon, 7 Sep 2026 21:38:44 -0400 Message-ID: <20260908013844.1788726-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090309-negation-laboring-bb8a@gregkh> References: <2026090309-negation-laboring-bb8a@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 raw firmware revision while limiting parsing to the v3-sized register prefix ] 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 60d2548f0eea4..531777557b47c 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -768,7 +768,6 @@ 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; @@ -1289,10 +1288,20 @@ static int cppc_set_reg_val(int cpu, enum cppc_regs reg_idx, u64 val) * @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_reg_val(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 e23d9abea1359..0330bc25fbe1a 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -766,7 +766,7 @@ 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