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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 16BCAC433E0 for ; Wed, 13 Jan 2021 15:38:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA54A23383 for ; Wed, 13 Jan 2021 15:38:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727225AbhAMPiV (ORCPT ); Wed, 13 Jan 2021 10:38:21 -0500 Received: from foss.arm.com ([217.140.110.172]:38248 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726113AbhAMPiV (ORCPT ); Wed, 13 Jan 2021 10:38:21 -0500 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 DAA071FB; Wed, 13 Jan 2021 07:37:34 -0800 (PST) Received: from [192.168.1.179] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A3C8B3F66E; Wed, 13 Jan 2021 07:37:33 -0800 (PST) Subject: Re: [PATCH] drm/panfrost: Use delayed timer as default in devfreq profile To: Lukasz Luba , linux-kernel@vger.kernel.org, airlied@linux.ie, daniel@ffwll.ch, dri-devel@lists.freedesktop.org Cc: robh@kernel.org, tomeu.vizoso@collabora.com, alyssa.rosenzweig@collabora.com References: <20210105164111.30122-1-lukasz.luba@arm.com> From: Steven Price Message-ID: <5a52797c-eb03-3dcc-932f-14a08828799e@arm.com> Date: Wed, 13 Jan 2021 15:35:37 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210105164111.30122-1-lukasz.luba@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/01/2021 16:41, Lukasz Luba wrote: > Devfreq framework supports 2 modes for monitoring devices. > Use delayed timer as default instead of deferrable timer > in order to monitor the GPU status regardless of CPU idle. > > Signed-off-by: Lukasz Luba Looks reasonable to me. Reviewed-by: Steven Price I'll apply to drm-misc-next. > --- > Hi all, > > This is just a simple change but has impact on reliable polling mode > with guaranteed sampling rate. The devfreq framework has 2 modes for > checking the device status which updates the statistics. When the > default mode is used (deferred work) it could happen that the > framework won't check the device, if the CPU which was running devfreq > code went idle. In deferred mode, the deferred timer is not fired, > thus framework won't check the device status. > > The log below is taken when glxgears was running. It can be seen that > periodic checks are missing (should be every 50ms). > > ---------------------------------------------------------------------- > > [ 128.046555] panfrost ff9a0000.gpu: busy 18029406 total 67940380 26 % freq 200 MHz > [ 128.110538] panfrost ff9a0000.gpu: busy 7975930 total 63980997 12 % freq 200 MHz > [ 128.210606] panfrost ff9a0000.gpu: busy 21148792 total 100074440 21 % freq 200 MHz > [ 128.594638] panfrost ff9a0000.gpu: busy 53739467 total 384032219 13 % freq 200 MHz > [ 129.178749] panfrost ff9a0000.gpu: busy 89206245 total 584111500 15 % freq 200 MHz > [ 129.294601] panfrost ff9a0000.gpu: busy 16446118 total 115852915 14 % freq 200 MHz > [ 129.762616] panfrost ff9a0000.gpu: busy 71481587 total 468015722 15 % freq 200 MHz > [ 129.874762] panfrost ff9a0000.gpu: busy 15614112 total 112139938 13 % freq 200 MHz > [ 130.026585] panfrost ff9a0000.gpu: busy 21397620 total 151821546 14 % freq 200 MHz > [ 130.110536] panfrost ff9a0000.gpu: busy 21429365 total 83952016 25 % freq 200 MHz > [ 130.178524] panfrost ff9a0000.gpu: busy 16458197 total 67989072 24 % freq 200 MHz > [ 130.246528] panfrost ff9a0000.gpu: busy 9876225 total 68004030 14 % freq 200 MHz > [ 130.310529] panfrost ff9a0000.gpu: busy 9211725 total 64000524 14 % freq 200 MHz > [ 130.410528] panfrost ff9a0000.gpu: busy 21780828 total 99999250 21 % freq 200 MHz > > ---------------------------------------------------------------------- > > It has impact on devfreq cooling and thermal governor. They rely on these > statistics, but sometimes the data is stale. > > This patch switches to more reliable devfreq mode, which uses delayed work. > > Regards, > Lukasz > > > drivers/gpu/drm/panfrost/panfrost_devfreq.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c > index f44d28fad085..56b3f5935703 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c > +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c > @@ -76,6 +76,7 @@ static int panfrost_devfreq_get_dev_status(struct device *dev, > } > > static struct devfreq_dev_profile panfrost_devfreq_profile = { > + .timer = DEVFREQ_TIMER_DELAYED, > .polling_ms = 50, /* ~3 frames */ > .target = panfrost_devfreq_target, > .get_dev_status = panfrost_devfreq_get_dev_status, >