From patchwork Fri May 12 09:57:42 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lukasz Luba X-Patchwork-Id: 13238986 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4949AC77B7F for ; Fri, 12 May 2023 10:00:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240663AbjELKAL (ORCPT ); Fri, 12 May 2023 06:00:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53550 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240654AbjELJ7a (ORCPT ); Fri, 12 May 2023 05:59:30 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 47F5811DB4; Fri, 12 May 2023 02:59:03 -0700 (PDT) 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 2E08D1684; Fri, 12 May 2023 02:59:30 -0700 (PDT) Received: from e123648.arm.com (unknown [10.57.22.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id E19C93F5A1; Fri, 12 May 2023 02:58:42 -0700 (PDT) From: Lukasz Luba To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, rafael@kernel.org Cc: lukasz.luba@arm.com, dietmar.eggemann@arm.com, rui.zhang@intel.com, amit.kucheria@verdurent.com, amit.kachhap@gmail.com, daniel.lezcano@linaro.org, viresh.kumar@linaro.org, len.brown@intel.com, pavel@ucw.cz, Pierre.Gondois@arm.com, ionela.voinescu@arm.com, rostedt@goodmis.org, mhiramat@kernel.org Subject: [PATCH v2 16/17] Documentation: EM: Add example with driver modifying the EM Date: Fri, 12 May 2023 10:57:42 +0100 Message-Id: <20230512095743.3393563-17-lukasz.luba@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230512095743.3393563-1-lukasz.luba@arm.com> References: <20230512095743.3393563-1-lukasz.luba@arm.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org The Energy Model (EM) support runtime modifications. Add description with example driver code which updates EM. Signed-off-by: Lukasz Luba --- Documentation/power/energy-model.rst | 53 ++++++++++++++++++++++++++-- 1 file changed, 51 insertions(+), 2 deletions(-) diff --git a/Documentation/power/energy-model.rst b/Documentation/power/energy-model.rst index 64c2462dc9a6..a6ceeeb72868 100644 --- a/Documentation/power/energy-model.rst +++ b/Documentation/power/energy-model.rst @@ -225,8 +225,11 @@ or in Section 3.4 :export: -4. Example driver ------------------ +4. Examples +----------- + +4.1 Example driver with EM registration +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The CPUFreq framework supports dedicated callback for registering the EM for a given CPU(s) 'policy' object: cpufreq_driver::register_em(). @@ -280,3 +283,49 @@ EM framework:: 39 static struct cpufreq_driver foo_cpufreq_driver = { 40 .register_em = foo_cpufreq_register_em, 41 }; + + +4.2 Example driver with EM modification +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +This section provides a simple example of a thermal driver modifying the EM. +The driver implements a foo_mod_power() function to be provided to the +EM framework. The driver is woken up periodically to check the temperature +and modify the EM data if needed:: + + -> drivers/thermal/foo_thermal.c + + 01 static int foo_mod_power(struct device *dev, unsigned long freq, + 02 unsigned long *power, void *priv) + 03 { + 04 struct foo_context *ctx = priv; + 05 + 06 /* Estimate power for the given frequency and temperature */ + 07 *power = foo_estimate_power(dev, freq, ctx->temperature); + 08 if (*power >= EM_MAX_POWER); + 09 return -EINVAL; + 10 + 11 return 0; + 12 } + 13 + 14 /* + 15 * Function called periodically to check the temperature and + 16 * update the EM if needed + 17 */ + 18 static void foo_thermal_em_update(struct foo_context *ctx) + 19 { + 20 struct em_data_callback em_cb = EM_UPDATE_CB(mod_power); + 21 struct cpufreq_policy *policy = ctx->policy; + 22 struct device *cpu_dev; + 23 + 24 cpu_dev = get_cpu_device(cpumask_first(policy->cpus)); + 25 + 26 ctx->temperature = foo_get_temp(cpu_dev, ctx); + 27 if (ctx->temperature < FOO_EM_UPDATE_TEMP_THRESHOLD) + 28 return; + 29 + 30 /* Update EM for the CPUs' performance domain */ + 31 ret = em_dev_update_perf_domain(cpu_dev, &em_cb, ctx); + 32 if (ret) + 33 pr_warn("foo_thermal: EM update failed\n"); + 34 }