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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 982EEC55194 for ; Fri, 24 Apr 2020 09:22:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 78B5720774 for ; Fri, 24 Apr 2020 09:22:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726747AbgDXJWM (ORCPT ); Fri, 24 Apr 2020 05:22:12 -0400 Received: from foss.arm.com ([217.140.110.172]:58060 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726726AbgDXJWM (ORCPT ); Fri, 24 Apr 2020 05:22:12 -0400 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 CEBB81FB; Fri, 24 Apr 2020 02:22:11 -0700 (PDT) Received: from [10.37.12.92] (unknown [10.37.12.92]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1A5703F73D; Fri, 24 Apr 2020 02:22:06 -0700 (PDT) Subject: Re: [PATCH] thermal: power_allocate: add upper and lower limits To: Michael Kao , Zhang Rui , Eduardo Valentin , Daniel Lezcano , Rob Herring , Mark Rutland , Matthias Brugger , hsinyi@chromium.org, linux-pm@vger.kernel.org, srv_heupstream@mediatek.com Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org References: <20200424071601.2636-1-michael.kao@mediatek.com> From: Lukasz Luba Message-ID: Date: Fri, 24 Apr 2020 10:22:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200424071601.2636-1-michael.kao@mediatek.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Hi Michael, On 4/24/20 8:16 AM, Michael Kao wrote: > The upper and lower limits of thermal throttle state in the > device tree do not apply to the power_allocate governor. > Add the upper and lower limits to the power_allocate governor. > > Signed-off-by: Michael Kao > --- > drivers/thermal/thermal_core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c > index 9a321dc548c8..f6feed2265bd 100644 > --- a/drivers/thermal/thermal_core.c > +++ b/drivers/thermal/thermal_core.c > @@ -598,7 +598,7 @@ int power_actor_set_power(struct thermal_cooling_device *cdev, > if (ret) > return ret; > > - instance->target = state; > + instance->target = clamp_val(state, instance->lower, instance->upper); > mutex_lock(&cdev->lock); > cdev->updated = false; > mutex_unlock(&cdev->lock); > Thank you for the patch and having to look at it. I have some concerns with this approach. Let's analyze it further. In default the cooling devices in the thermal zone which is used by IPA do not have this 'lower' and 'upper' limits. They are set to THERMAL_NO_LIMIT in DT to give full control to IPA over the states. This the function 'power_actor_set_power' actually translates granted power to the state that device will run for the next period. The IPA algorithm has already split the power budget. Now what happen when the 'lower' value will change the state to a state which consumes more power than was calculated in the IPA alg... It will became unstable. I would rather see a change which uses these 'lower' and 'upper' limits before the IPA do the calculation of the power budget. But this wasn't a requirement and we assumed that IPA has full control over the cooling device (which I described above with this DT THERMAL_NO_LIMIT). Is there a problem with your platform that it has to provide some minimal performance, so you tried to introduce this clamping? Regards, Lukasz