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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 B14E5C83000 for ; Wed, 29 Apr 2020 20:24:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91C11208E0 for ; Wed, 29 Apr 2020 20:24:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726743AbgD2UYw (ORCPT ); Wed, 29 Apr 2020 16:24:52 -0400 Received: from foss.arm.com ([217.140.110.172]:44566 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726456AbgD2UYw (ORCPT ); Wed, 29 Apr 2020 16:24:52 -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 D6F311063; Wed, 29 Apr 2020 13:24:48 -0700 (PDT) Received: from [10.37.12.43] (unknown [10.37.12.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9EF1A3F68F; Wed, 29 Apr 2020 13:24:45 -0700 (PDT) Subject: Re: [PATCH] thermal: power_allocate: add upper and lower limits To: Michael Kao Cc: Zhang Rui , Eduardo Valentin , Daniel Lezcano , Rob Herring , Mark Rutland , Matthias Brugger , hsinyi@chromium.org, linux-pm@vger.kernel.org, srv_heupstream@mediatek.com, 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> <1588156776.3573.1.camel@mtksdccf07> From: Lukasz Luba Message-ID: <03286571-c110-7f5e-a911-24f8c3e4fd42@arm.com> Date: Wed, 29 Apr 2020 21:24:43 +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: <1588156776.3573.1.camel@mtksdccf07> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 4/29/20 11:39 AM, Michael Kao wrote: > On Fri, 2020-04-24 at 10:22 +0100, Lukasz Luba wrote: >> 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 > > > Hi Lukasz, > > I refer to the documentation settings of the thermal device tree > (Documentation / devicetree / bindings / thermal / thermal.txt). > > It shows that cooling-device is a mandatory property, so max/min cooling > state should be able to support in framework point of view. > Otherwise, the limitation should be added in binding document. > > Different hardware mechanisms have different heat dissipation > capabilities. > Limiting the input heat source can slow down the heat accumulation and > temperature burst. > We want to reduce the accumulation of heat at high temperature by > limiting the minimum gear of thermal throttle. I agree that these 'lower' and 'upper' limits shouldn't be just ignored as is currently. This patch clamps the value at late stage, though. Let me have a look how it could be taken into account in the early stage, before the power calculation and split are done. Maybe there is a clean way to inject this. Regards, Lukasz