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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 81C82C83000 for ; Wed, 29 Apr 2020 15:50:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 64B5F20B80 for ; Wed, 29 Apr 2020 15:50:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726519AbgD2PuH (ORCPT ); Wed, 29 Apr 2020 11:50:07 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:44078 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726511AbgD2PuH (ORCPT ); Wed, 29 Apr 2020 11:50:07 -0400 Received: from 185.80.35.16 (185.80.35.16) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.415) id bb23fa4412e3993e; Wed, 29 Apr 2020 17:50:04 +0200 From: "Rafael J. Wysocki" To: Benjamin Gaignard Cc: viresh.kumar@linaro.org, hugues.fruchet@st.com, mchehab@kernel.org, mcoquelin.stm32@gmail.com, alexandre.torgue@st.com, pavel@ucw.cz, len.brown@intel.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, Patrick Bellasi Subject: Re: [RFC 0/3] Introduce cpufreq minimum load QoS Date: Wed, 29 Apr 2020 17:50:04 +0200 Message-ID: <7657495.QyJl4BcWH5@kreacher> In-Reply-To: <20200424114058.21199-1-benjamin.gaignard@st.com> References: <20200424114058.21199-1-benjamin.gaignard@st.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Friday, April 24, 2020 1:40:55 PM CEST Benjamin Gaignard wrote: > When start streaming from the sensor the CPU load could remain very low > because almost all the capture pipeline is done in hardware (i.e. without > using the CPU) and let believe to cpufreq governor that it could use lower > frequencies. If the governor decides to use a too low frequency that > becomes a problem when we need to acknowledge the interrupt during the > blanking time. > The delay to ack the interrupt and perform all the other actions before > the next frame is very short and doesn't allow to the cpufreq governor to > provide the required burst of power. That led to drop the half of the frames. > > To avoid this problem, DCMI driver informs the cpufreq governors by adding > a cpufreq minimum load QoS resquest. This seems to be addressing a use case that can be addressed with the help of utilization clamps with less power overhead. Thanks!