From nobody Mon Feb 9 17:35:39 2026 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 7C0E7C77B7F for ; Fri, 12 May 2023 10:00:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240731AbjELKAV (ORCPT ); Fri, 12 May 2023 06:00:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53278 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240751AbjELJ7u (ORCPT ); Fri, 12 May 2023 05:59:50 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 09ABB12E90; Fri, 12 May 2023 02:59:10 -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 27D9B16F2; Fri, 12 May 2023 02:59:33 -0700 (PDT) Received: from e123648.arm.com (unknown [10.57.22.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id DEB273F5A1; Fri, 12 May 2023 02:58:45 -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 17/17] Documentation: EM: Describe the API of runtime modifications Date: Fri, 12 May 2023 10:57:43 +0100 Message-Id: <20230512095743.3393563-18-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 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Describe the Energy Model runtime modification API and how it can be used. Signed-off-by: Lukasz Luba --- Documentation/power/energy-model.rst | 31 ++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) diff --git a/Documentation/power/energy-model.rst b/Documentation/power/ene= rgy-model.rst index a6ceeeb72868..2fd6e82a8124 100644 --- a/Documentation/power/energy-model.rst +++ b/Documentation/power/energy-model.rst @@ -213,10 +213,37 @@ CPUfreq governor is in use in case of CPU device. Cur= rently this calculation is not provided for other type of devices. =20 More details about the above APIs can be found in ``= `` -or in Section 3.4 +or in Section 3.5 =20 =20 -3.4 Description details of this API +3.4 Runtime modifications +^^^^^^^^^^^^^^^^^^^^^^^^^ + +Drivers willing to modify the EM at runtime should use the following API:: + + + int em_dev_update_perf_domain(struct device *dev, + struct em_data_callback *cb, void *priv); + +Drivers must provide a callback .update_power() returning power value for = each +performance state. The callback function provided by the driver is free +to fetch data from any relevant location (DT, firmware, ...) or sensor. +The .update_power() callback is called by the EM for each performance stat= e to +provide new power value. In the Section 4.2 there is an example driver +which shows simple implementation of this mechanism. The callback can be +declared with EM_UPDATE_CB() macro. The caller of that callback also passes +a private void pointer back to the driver which tries to update EM. +It is useful and helps to maintain the consistent context for all performa= nce +state calls for a given EM. +The artificial EM also supports runtime modifications. For this type of EM +there is a need to provide one more callback: .get_cost(). The .get_cost() +returns the cost value for each performance state, which better reflects t= he +efficiency of the CPUs which use artificial EM. Those two callbacks: +.update_power() and get .get_cost() can be declared with one macro +EM_ADV_UPDATE_CB() and then passed to the em_dev_update_perf_domain(). + + +3.5 Description details of this API ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ .. kernel-doc:: include/linux/energy_model.h :internal: --=20 2.25.1