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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jTtGI-0005Xt-1L; Wed, 29 Apr 2020 20:24:54 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jTtGE-0005XK-1t; Wed, 29 Apr 2020 20:24:52 +0000 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 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-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200429_132450_185148_049839CA X-CRM114-Status: GOOD ( 25.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , devicetree@vger.kernel.org, srv_heupstream@mediatek.com, linux-pm@vger.kernel.org, Daniel Lezcano , linux-kernel@vger.kernel.org, Eduardo Valentin , Rob Herring , linux-mediatek@lists.infradead.org, hsinyi@chromium.org, Matthias Brugger , Zhang Rui , linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel