From patchwork Tue Sep 1 17:29:55 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 256876 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 052EAC433E6 for ; Tue, 1 Sep 2020 17:40:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E37FB207D3 for ; Tue, 1 Sep 2020 17:40:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728900AbgIARjz (ORCPT ); Tue, 1 Sep 2020 13:39:55 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:59386 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728192AbgIARjy (ORCPT ); Tue, 1 Sep 2020 13:39:54 -0400 Received: from 89-64-88-247.dynamic.chello.pl (89.64.88.247) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.459) id 4763ca42f0cd1aa2; Tue, 1 Sep 2020 19:39:52 +0200 From: "Rafael J. Wysocki" To: Linux PM Cc: Srinivas Pandruvada , LKML , Doug Smythies , Artem Bityutskiy Subject: [PATCH v4 3/5] cpufreq: intel_pstate: Tweak the EPP sysfs interface Date: Tue, 01 Sep 2020 19:29:55 +0200 Message-ID: <5280698.oOqPgdve7T@kreacher> In-Reply-To: <3748218.V0HrpZKF9g@kreacher> References: <3748218.V0HrpZKF9g@kreacher> MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org From: "Rafael J. Wysocki" Modify the EPP sysfs interface to reject attempts to change the EPP to values different from 0 ("performance") in the active mode with the "performance" policy (ie. scaling_governor set to "performance"), to avoid situations in which the kernel appears to discard data passed to it via the EPP sysfs attribute. Signed-off-by: Rafael J. Wysocki Reviewed-by: Artem Bityutskiy --- v2 -> v3: New patch v3 -> v4: Add the R-by from Artem --- Documentation/admin-guide/pm/intel_pstate.rst | 4 +++- drivers/cpufreq/intel_pstate.c | 8 ++++++++ 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst index cdd1a9a7f9a2..5072e7064d13 100644 --- a/Documentation/admin-guide/pm/intel_pstate.rst +++ b/Documentation/admin-guide/pm/intel_pstate.rst @@ -123,7 +123,9 @@ Energy-Performance Bias (EPB) knob (otherwise), which means that the processor's internal P-state selection logic is expected to focus entirely on performance. This will override the EPP/EPB setting coming from the ``sysfs`` interface -(see `Energy vs Performance Hints`_ below). +(see `Energy vs Performance Hints`_ below). Moreover, any attempts to change +the EPP/EPB to a value different from 0 ("performance") via ``sysfs`` in this +configuration will be rejected. Also, in this configuration the range of P-states available to the processor's internal P-state selection logic is always restricted to the upper boundary diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index e540448e0bd0..b308c39b6204 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -684,6 +684,14 @@ static int intel_pstate_set_energy_pref_index(struct cpudata *cpu_data, else if (epp == -EINVAL) epp = epp_values[pref_index - 1]; + /* + * To avoid confusion, refuse to set EPP to any values different + * from 0 (performance) if the current policy is "performance", + * because those values would be overridden. + */ + if (epp > 0 && cpu_data->policy == CPUFREQ_POLICY_PERFORMANCE) + return -EBUSY; + ret = intel_pstate_set_epp(cpu_data, epp); } else { if (epp == -EINVAL)