From mboxrd@z Thu Jan 1 00:00:00 1970 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9773FC433EF for ; Fri, 29 Oct 2021 13:05:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D04C61165 for ; Fri, 29 Oct 2021 13:05:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231607AbhJ2NI0 (ORCPT ); Fri, 29 Oct 2021 09:08:26 -0400 Received: from mail-bn8nam12on2065.outbound.protection.outlook.com ([40.107.237.65]:27498 "EHLO NAM12-BN8-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S231929AbhJ2NHp (ORCPT ); Fri, 29 Oct 2021 09:07:45 -0400 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=ijtAbYxDPAq0/iKYKhsRAJeRtN9tMSOH84JAeMgHgyi2+H+4VXQ2CGTxYNGRkt2XCFargCo48R3h0jZl6HgQaD4IHpELaBkI9ZDnUfsOdUqbvvirC0fYnBDQlDcKyxMfVepg2IHup+36ggNScv3jgBqpBR3RDaiwEX/Dh9MQXbT8XlMZ+TclcG5ZrQiNxXNnGoRHWFJursyZkSKev9drMPC4foYwKMi+FbSfDm8k9mQm7cVs1pX7SbSD1S0odIiXeK3TuzWzofq+WhZ1seN0Le3zUzGAAYLYMs8a0oh/JtTCJCT5tHusdV8PnOlZunzZuULgCm9ZlznItSNTO9gwhQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=qIpMTBJ3EqyeHUirXhvoCCS4sE29iB035X8KM51Alj4=; b=SaZUpejTzcLw5tnyCvwIo0kJrgbKsg0vYcT1jenYdo9EfS5gyVLzjaGCTf1qvQkSAKRMsvYclzcxPezCSoz5oXODLR3qWk+/mxd5p58PULTc2Ck/E4CS+BXndRuB+vdmlWF0XFY9RVnF/arkWIb4Kbq6upMenqPka5PV8Qff7IOow7/ohXagXzbnMMoqPte2qPpEIE7NguRYtfvNjJ9Z5RxYo1eGV+ogjLuHhNm7uQSKSgQre1mkX2Qh/Y6q21QLVHWy5DqMxuCfyyfUD52sKOYkONJntmNgudZC49ddEjTeZyrij8IUF6ky5TBd+fdsUy2fjD3hgQX23PhcW/Tt1w== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 165.204.84.17) smtp.rcpttodomain=intel.com smtp.mailfrom=amd.com; dmarc=pass (p=quarantine sp=quarantine pct=100) action=none header.from=amd.com; dkim=none (message not signed); arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=qIpMTBJ3EqyeHUirXhvoCCS4sE29iB035X8KM51Alj4=; b=3b4Xs+x1NmBxXWU/VVhYljs0JakldNq0I1KzaT6xASKUqy3OYu0zBwq7yuOSReRSjB3Q8lxWVZmFBLKVxE8mNNlyggCDpeP11PjwwoOV/L9TOLoHjLRBL4n9hECI+82ofErstDTN8CpyIuKc+86Q3Impg8szFn7eD2wM+cJMoG4= Received: from BN9PR03CA0371.namprd03.prod.outlook.com (2603:10b6:408:f7::16) by BN7PR12MB2724.namprd12.prod.outlook.com (2603:10b6:408:31::28) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4649.14; Fri, 29 Oct 2021 13:05:12 +0000 Received: from BN8NAM11FT012.eop-nam11.prod.protection.outlook.com (2603:10b6:408:f7:cafe::ee) by BN9PR03CA0371.outlook.office365.com (2603:10b6:408:f7::16) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4649.14 via Frontend Transport; Fri, 29 Oct 2021 13:05:12 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 165.204.84.17) smtp.mailfrom=amd.com; intel.com; dkim=none (message not signed) header.d=none;intel.com; dmarc=pass action=none header.from=amd.com; Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; Received: from SATLEXMB04.amd.com (165.204.84.17) by BN8NAM11FT012.mail.protection.outlook.com (10.13.177.55) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.4649.14 via Frontend Transport; Fri, 29 Oct 2021 13:05:11 +0000 Received: from hr-amd.amd.com (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Fri, 29 Oct 2021 08:04:55 -0500 From: Huang Rui To: "Rafael J . Wysocki" , Viresh Kumar , Shuah Khan , "Borislav Petkov" , Peter Zijlstra , Ingo Molnar , Giovanni Gherdovich , CC: Deepak Sharma , Alex Deucher , Mario Limonciello , Steven Noonan , Nathan Fontenot , Jinzhou Su , Xiaojian Du , , , Huang Rui Subject: [PATCH v3 21/21] Documentation: amd-pstate: add amd-pstate driver introduction Date: Fri, 29 Oct 2021 21:02:41 +0800 Message-ID: <20211029130241.1984459-22-ray.huang@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211029130241.1984459-1-ray.huang@amd.com> References: <20211029130241.1984459-1-ray.huang@amd.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: af2e3f79-11df-4d38-3420-08d99adcbd71 X-MS-TrafficTypeDiagnostic: BN7PR12MB2724: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(4636009)(36840700001)(46966006)(186003)(316002)(7696005)(5660300002)(16526019)(356005)(6666004)(426003)(54906003)(26005)(110136005)(82310400003)(36860700001)(508600001)(47076005)(81166007)(70206006)(1076003)(36756003)(86362001)(2906002)(336012)(70586007)(8936002)(4326008)(83380400001)(2616005)(30864003)(966005)(7416002)(8676002)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Oct 2021 13:05:11.0761 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: af2e3f79-11df-4d38-3420-08d99adcbd71 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT012.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN7PR12MB2724 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Introduce the amd-pstate driver design and implementation. Signed-off-by: Huang Rui --- Documentation/admin-guide/pm/amd-pstate.rst | 373 ++++++++++++++++++ .../admin-guide/pm/working-state.rst | 1 + 2 files changed, 374 insertions(+) create mode 100644 Documentation/admin-guide/pm/amd-pstate.rst diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst new file mode 100644 index 000000000000..375374e3eb80 --- /dev/null +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -0,0 +1,373 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: + +=============================================== +``amd-pstate`` CPU Performance Scaling Driver +=============================================== + +:Copyright: |copy| 2021 Advanced Micro Devices, Inc. + +:Author: Huang Rui + + +Introduction +=================== + +``amd-pstate`` is the AMD CPU performance scaling driver that introduces a +new CPU frequency control mechanism on modern AMD APU and CPU series in +Linux kernel. The new mechanism is based on Collaborative Processor +Performance Control (CPPC) which provides finer grain frequency management +than legacy ACPI hardware P-States. Current AMD CPU/APU platforms are using +the ACPI P-states driver to manage CPU frequency and clocks with switching +only in 3 P-states. CPPC replaces the ACPI P-states controls, allows a +flexible, low-latency interface for the Linux kernel to directly +communicate the performance hints to hardware. + +``amd-pstate`` leverages the Linux kernel governors such as ``schedutil``, +``ondemand``, etc. to manage the performance hints which are provided by +CPPC hardware functionality that internally follows the hardware +specification (for details refer to AMD64 Architecture Programmer's Manual +Volume 2: System Programming [1]_). Currently ``amd-pstate`` supports basic +frequency control function according to kernel governors on some of the +Zen2 and Zen3 processors, and we will implement more AMD specific functions +in future after we verify them on the hardware and SBIOS. + + +AMD CPPC Overview +======================= + +Collaborative Processor Performance Control (CPPC) interface enumerates a +continuous, abstract, and unit-less performance value in a scale that is +not tied to a specific performance state / frequency. This is an ACPI +standard [2]_ which software can specify application performance goals and +hints as a relative target to the infrastructure limits. AMD processors +provides the low latency register model (MSR) instead of AML code +interpreter for performance adjustments. ``amd-pstate`` will initialize a +``struct cpufreq_driver`` instance ``amd_pstate_driver`` with the callbacks +to manage each performance update behavior. :: + + Highest Perf ------>+-----------------------+ +-----------------------+ + | | | | + | | | | + | | Max Perf ---->| | + | | | | + | | | | + Nominal Perf ------>+-----------------------+ +-----------------------+ + | | | | + | | | | + | | | | + | | | | + | | | | + | | | | + | | Desired Perf ---->| | + | | | | + | | | | + | | | | + | | | | + | | | | + | | | | + | | | | + | | | | + | | | | + Lowest non- | | | | + linear perf ------>+-----------------------+ +-----------------------+ + | | | | + | | Lowest perf ---->| | + | | | | + Lowest perf ------>+-----------------------+ +-----------------------+ + | | | | + | | | | + | | | | + 0 ------>+-----------------------+ +-----------------------+ + + AMD P-States Performance Scale + + +.. _perf_cap: + +AMD CPPC Performance Capability +-------------------------------- + +Highest Performance (RO) +......................... + +It is the absolute maximum performance an individual processor may reach, +assuming ideal conditions. This performance level may not be sustainable +for long durations and may only be achievable if other platform components +are in a specific state; for example, it may require other processors be in +an idle state. This would be equivalent to the highest frequencies +supported by the processor. + +Nominal (Guaranteed) Performance (RO) +...................................... + +It is the maximum sustained performance level of the processor, assuming +ideal operating conditions. In absence of an external constraint (power, +thermal, etc.) this is the performance level the processor is expected to +be able to maintain continuously. All cores/processors are expected to be +able to sustain their nominal performance state simultaneously. + +Lowest non-linear Performance (RO) +................................... + +It is the lowest performance level at which nonlinear power savings are +achieved, for example, due to the combined effects of voltage and frequency +scaling. Above this threshold, lower performance levels should be generally +more energy efficient than higher performance levels. This register +effectively conveys the most efficient performance level to ``amd-pstate``. + +Lowest Performance (RO) +........................ + +It is the absolute lowest performance level of the processor. Selecting a +performance level lower than the lowest nonlinear performance level may +cause an efficiency penalty but should reduce the instantaneous power +consumption of the processor. + +AMD CPPC Performance Control +------------------------------ + +``amd-pstate`` passes performance goals through these registers. The +register drives the behavior of the desired performance target. + +Minimum requested performance (RW) +................................... + +``amd-pstate`` specifies the minimum allowed performance level. + +Maximum requested performance (RW) +................................... + +``amd-pstate`` specifies a limit the maximum performance that is expected +to be supplied by the hardware. + +Desired performance target (RW) +................................... + +``amd-pstate`` specifies a desired target in the CPPC performance scale as +a relative number. This can be expressed as percentage of nominal +performance (infrastructure max). Below the nominal sustained performance +level, desired performance expresses the average performance level of the +processor subject to hardware. Above the nominal performance level, +processor must provide at least nominal performance requested and go higher +if current operating conditions allow. + +Energy Performance Preference (EPP) (RW) +......................................... + +Provides a hint to the hardware if software wants to bias toward performance +(0x0) or energy efficiency (0xff). + + +Key Governors Support +======================= + +``amd-pstate`` can be used with all the (generic) scaling governors listed +by the ``scaling_available_governors`` policy attribute in ``sysfs``. Then, +it is responsible for the configuration of policy objects corresponding to +CPUs and provides the ``CPUFreq`` core (and the scaling governors attached +to the policy objects) with accurate information on the maximum and minimum +operating frequencies supported by the hardware. Users can check the +``scaling_cur_freq`` information comes from the ``CPUFreq`` core. + +``amd-pstate`` mainly supports ``schedutil`` and ``ondemand`` for dynamic +frequency control. It is to fine tune the processor configuration on +``amd-pstate`` to the ``schedutil`` with CPU CFS scheduler. ``amd-pstate`` +registers adjust_perf callback to implement the CPPC similar performance +update behavior. It is initialized by ``sugov_start`` and then populate the +CPU's update_util_data pointer to assign ``sugov_update_single_perf`` as +the utilization update callback function in CPU scheduler. CPU scheduler +will call ``cpufreq_update_util`` and assign the target performance +according to the ``struct sugov_cpu`` that utilization update belongs to. +Then ``amd-pstate`` updates the desired performance according to the CPU +scheduler assigned. + + +Processor Support +======================= + +The ``amd-pstate`` initialization will fail if the _CPC in ACPI SBIOS is +not existed at the detected processor, and it uses ``acpi_cpc_valid`` to +check the _CPC existence. All Zen based processors support legacy ACPI +hardware P-States function, so while the ``amd-pstate`` fails to be +initialized, the kernel will fall back to initialize ``acpi-cpufreq`` +driver. + +There are two types of hardware implementations for ``amd-pstate``: one is +`Full MSR Support `_ and another is `Shared Memory Support +`_. It can use :c:macro:`X86_FEATURE_AMD_CPPC` feature flag (for +details refer to Processor Programming Reference (PPR) for AMD Family +19h Model 21h, Revision B0 Processors [3]_) to indicate the different +types. ``amd-pstate`` is to register different ``amd_pstate_perf_funcs`` +instances for different hardware implementations. + +Currently, some of Zen2 and Zen3 processors support ``amd-pstate``. In the +future, it will be supported on more and more AMD processors. + +Full MSR Support +----------------- + +Some new Zen3 processors such as Cezanne provide the MSR registers directly +while the :c:macro:`X86_FEATURE_AMD_CPPC` CPU feature flag is set. +``amd-pstate`` can handle the MSR register to implement the fast switch +function in ``CPUFreq`` that can shrink latency of frequency control on the +interrupt context. + +Shared Memory Support +---------------------- + +If :c:macro:`X86_FEATURE_AMD_CPPC` CPU feature flag is not set, that means +the processor supports shared memory solution. In this case, ``amd-pstate`` +uses the ``cppc_acpi`` helper methods to implement the callback functions +of ``amd_pstate_perf_funcs``. + + +AMD P-States and ACPI hardware P-States always can be supported in one +processor. But AMD P-States has the higher priority and if it is enabled +with :c:macro:`MSR_AMD_CPPC_ENABLE` or ``cppc_set_enable``, it will respond +to the request from AMD P-States. + + +User Space Interface in ``sysfs`` +================================== + +``amd-pstate`` exposes several global attributes (files) in ``sysfs`` to +control its functionality at the system level. They located in the +``/sys/devices/system/cpu/cpufreq/policyX/`` directory and affect all CPUs. :: + + root@hr-test1:/home/ray# ls /sys/devices/system/cpu/cpufreq/policy0/*amd* + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_highest_perf + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_lowest_nonlinear_freq + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_lowest_nonlinear_perf + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_lowest_perf + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_max_freq + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_min_freq + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_nominal_freq + /sys/devices/system/cpu/cpufreq/policy0/amd_pstate_nominal_perf + + +``amd_pstate_highest_perf / amd_pstate_max_freq`` + +Maximum CPPC performance and CPU frequency that the driver is allowed to +set in percent of the maximum supported CPPC performance level (the highest +performance supported in `AMD CPPC Performance Capability `_). +This attribute is read-only. + +``amd_pstate_nominal_perf / amd_pstate_nominal_freq`` + +Nominal CPPC performance and CPU frequency that the driver is allowed to +set in percent of the maximum supported CPPC performance level (Please see +nominal performance in `AMD CPPC Performance Capability `_). +This attribute is read-only. + +``amd_pstate_lowest_nonlinear_perf / amd_pstate_lowest_nonlinear_freq`` + +The lowest non-linear CPPC performance and CPU frequency that the driver is +allowed to set in percent of the maximum supported CPPC performance level +(Please see the lowest non-linear performance in `AMD CPPC Performance +Capability `_). +This attribute is read-only. + +``amd_pstate_lowest_perf`` + +The lowest physical CPPC performance. The minimum CPU frequency can be read +back from ``cpuinfo`` member of ``cpufreq_policy``, so we won't expose it +here. +This attribute is read-only. + + +``amd-pstate`` vs ``acpi-cpufreq`` +====================================== + +On majority of AMD platforms supported by ``acpi-cpufreq``, the ACPI tables +provided by the platform firmware used for CPU performance scaling, but +only provides 3 P-states on AMD processors. +However, on modern AMD APU and CPU series, it provides the collaborative +processor performance control according to ACPI protocol and customize this +for AMD platforms. That is fine-grain and continuous frequency range +instead of the legacy hardware P-states. ``amd-pstate`` is the kernel +module which supports the new AMD P-States mechanism on most of future AMD +platforms. The AMD P-States mechanism will be the more performance and energy +efficiency frequency management method on AMD processors. + +``cpupower`` tool support for ``amd-pstate`` +=============================================== + +``amd-pstate`` is supported on ``cpupower`` tool that can be used to dump the frequency +information. And it is in progress to support more and more operations for new +``amd-pstate`` module with this tool. :: + + root@hr-test1:/home/ray# cpupower frequency-info + analyzing CPU 0: + driver: amd-pstate + CPUs which run at the same hardware frequency: 0 + CPUs which need to have their frequency coordinated by software: 0 + maximum transition latency: 131 us + hardware limits: 400 MHz - 4.68 GHz + available cpufreq governors: ondemand conservative powersave userspace performance schedutil + current policy: frequency should be within 400 MHz and 4.68 GHz. + The governor "schedutil" may decide which speed to use + within this range. + current CPU frequency: Unable to call hardware + current CPU frequency: 4.02 GHz (asserted by call to kernel) + boost state support: + Supported: yes + Active: yes + AMD PSTATE Highest Performance: 166. Maximum Frequency: 4.68 GHz. + AMD PSTATE Nominal Performance: 117. Nominal Frequency: 3.30 GHz. + AMD PSTATE Lowest Non-linear Performance: 39. Lowest Non-linear Frequency: 1.10 GHz. + AMD PSTATE Lowest Performance: 15. Lowest Frequency: 400 MHz. + + +Diagnostics and Tuning +======================= + +Trace Events +-------------- + +There are two static trace events that can be used for ``amd-pstate`` +diagnostics. One of them is the cpu_frequency trace event generally used +by ``CPUFreq``, and the other one is the ``amd_pstate_perf`` trace event +specific to ``amd-pstate``. The following sequence of shell commands can +be used to enable them and see their output (if the kernel is generally +configured to support event tracing). :: + + root@hr-test1:/home/ray# cd /sys/kernel/tracing/ + root@hr-test1:/sys/kernel/tracing# echo 1 > events/amd_cpu/enable + root@hr-test1:/sys/kernel/tracing# cat trace + # tracer: nop + # + # entries-in-buffer/entries-written: 47827/42233061 #P:2 + # + # _-----=> irqs-off + # / _----=> need-resched + # | / _---=> hardirq/softirq + # || / _--=> preempt-depth + # ||| / delay + # TASK-PID CPU# |||| TIMESTAMP FUNCTION + # | | | |||| | | + -0 [015] dN... 4995.979886: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=15 changed=false fast_switch=true + -0 [007] d.h.. 4995.979893: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=7 changed=false fast_switch=true + cat-2161 [000] d.... 4995.980841: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=0 changed=false fast_switch=true + sshd-2125 [004] d.s.. 4995.980968: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=4 changed=false fast_switch=true + -0 [007] d.s.. 4995.980968: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=7 changed=false fast_switch=true + -0 [003] d.s.. 4995.980971: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=3 changed=false fast_switch=true + -0 [011] d.s.. 4995.980996: amd_pstate_perf: amd_min_perf=85 amd_des_perf=85 amd_max_perf=166 cpu_id=11 changed=false fast_switch=true + +The cpu_frequency trace event will be triggered either by the ``schedutil`` scaling +governor (for the policies it is attached to), or by the ``CPUFreq`` core (for the +policies with other scaling governors). + + +Reference +=========== + +.. [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming, + https://www.amd.com/system/files/TechDocs/24593.pdf + +.. [2] Advanced Configuration and Power Interface Specification, + https://uefi.org/sites/default/files/resources/ACPI_Spec_6_4_Jan22.pdf + +.. [3] Processor Programming Reference (PPR) for AMD Family 19h Model 21h, Revision B0 Processors + https://www.amd.com/system/files/TechDocs/55898_B1_pub_0.50.zip + diff --git a/Documentation/admin-guide/pm/working-state.rst b/Documentation/admin-guide/pm/working-state.rst index f40994c422dc..5d2757e2de65 100644 --- a/Documentation/admin-guide/pm/working-state.rst +++ b/Documentation/admin-guide/pm/working-state.rst @@ -11,6 +11,7 @@ Working-State Power Management intel_idle cpufreq intel_pstate + amd-pstate cpufreq_drivers intel_epb intel-speed-select -- 2.25.1