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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C08AEB64DB for ; Tue, 20 Jun 2023 11:56:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232198AbjFTL4l (ORCPT ); Tue, 20 Jun 2023 07:56:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40872 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231144AbjFTL4i (ORCPT ); Tue, 20 Jun 2023 07:56:38 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id CAD1218C; Tue, 20 Jun 2023 04:56:36 -0700 (PDT) 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 6A7001063; Tue, 20 Jun 2023 04:57:20 -0700 (PDT) Received: from [10.57.26.18] (unknown [10.57.26.18]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B8E7B3F71E; Tue, 20 Jun 2023 04:56:34 -0700 (PDT) Message-ID: <62c35d1c-7dcd-7bf2-253e-65cdfd6e92cc@arm.com> Date: Tue, 20 Jun 2023 12:56:52 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH V4] thermal/core/power_allocator: reset thermal governor when trip point is changed To: "Rafael J. Wysocki" Cc: daniel.lezcano@linaro.org, rui.zhang@intel.com, Di Shen , amitk@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, xuewen.yan@unisoc.com, jeson.gao@unisoc.com, zhanglyra@gmail.com, orsonzhai@gmail.com References: <6aad180f-410c-5b11-b30b-c7bc02cbe054@linaro.org> <20230619063534.12831-1-di.shen@unisoc.com> Content-Language: en-US From: Lukasz Luba In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/20/23 11:39, Rafael J. Wysocki wrote: > On Tue, Jun 20, 2023 at 12:19 PM Lukasz Luba wrote: >> >> Hi Rafael, >> >> >> On 6/20/23 11:07, Rafael J. Wysocki wrote: >>> On Tue, Jun 20, 2023 at 11:46 AM Rafael J. Wysocki wrote: >>>> >>>> On Mon, Jun 19, 2023 at 8:36 AM Di Shen wrote: >>>>> >>>>> When the thermal trip point is changed, the governor should >>>>> be reset so that the policy algorithm be updated to adapt to the >>>>> new trip point. >>>>> >>>>> This patch adds an ops for thermal the governor structure to reset >>>>> the governor. The ops is called when the trip point is changed. >>>>> For power allocator, the parameters of pid controller and the states >>>>> of power cooling devices can be reset when the passive trip point >>>>> is changed. >>>>> >>>>> Signed-off-by: Di Shen >>>>> >>>>> --- >>>>> V4: >>>>> - Compared to V3, handle it in thermal core instead of in governor. >>>>> >>>>> - Add an ops to the governor structure, and call it when a trip >>>>> point is changed. >>>>> >>>>> - Define reset ops for power allocator. >>>>> >>>>> V3: >>>>> - Add fix tag. >>>>> >>>>> V2: >>>>> - Compared to v1, do not revert. >>>>> >>>>> - Add a variable(last_switch_on_temp) in power_allocator_params >>>>> to record the last switch_on_temp value. >>>>> >>>>> - Adds a function to renew the update flag and update the >>>>> last_switch_on_temp when thermal trips are writable. >>>>> >>>>> V1: >>>>> - Revert commit 0952177f2a1f. >>>>> --- >>>>> --- >>>>> drivers/thermal/gov_power_allocator.c | 21 +++++++++++++++++++++ >>>>> drivers/thermal/thermal_trip.c | 6 ++++++ >>>>> include/linux/thermal.h | 1 + >>>>> 3 files changed, 28 insertions(+) >>>>> >>>>> diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c >>>>> index 8642f1096b91..41d155adc616 100644 >>>>> --- a/drivers/thermal/gov_power_allocator.c >>>>> +++ b/drivers/thermal/gov_power_allocator.c >>>>> @@ -729,10 +729,31 @@ static int power_allocator_throttle(struct thermal_zone_device *tz, int trip_id) >>>>> return allocate_power(tz, trip.temperature); >>>>> } >>>>> >>>>> +static int power_allocator_reset(struct thermal_zone_device *tz, int trip_id) >>>>> +{ >>>>> + int ret = 0; >>>>> + struct thermal_trip trip; >>>>> + struct power_allocator_params *params = tz->governor_data; >>>>> + >>>>> + ret = __thermal_zone_get_trip(tz, trip_id, &trip); >>>>> + if (ret) >>>>> + return ret; >>>>> + >>>>> + /* Only need reset for passive trips */ >>>>> + if (trip.type != THERMAL_TRIP_PASSIVE) >>>>> + return -EINVAL; >>>>> + >>>>> + reset_pid_controller(params); >>>>> + allow_maximum_power(tz, true); >>>>> + >>>>> + return ret; >>>>> +} >>>>> + >>>>> static struct thermal_governor thermal_gov_power_allocator = { >>>>> .name = "power_allocator", >>>>> .bind_to_tz = power_allocator_bind, >>>>> .unbind_from_tz = power_allocator_unbind, >>>>> .throttle = power_allocator_throttle, >>>>> + .reset = power_allocator_reset, >>>>> }; >>>>> THERMAL_GOVERNOR_DECLARE(thermal_gov_power_allocator); >>>>> diff --git a/drivers/thermal/thermal_trip.c b/drivers/thermal/thermal_trip.c >>>>> index 907f3a4d7bc8..52eb768fada8 100644 >>>>> --- a/drivers/thermal/thermal_trip.c >>>>> +++ b/drivers/thermal/thermal_trip.c >>>>> @@ -173,6 +173,12 @@ int thermal_zone_set_trip(struct thermal_zone_device *tz, int trip_id, >>>>> if (tz->trips && (t.temperature != trip->temperature || t.hysteresis != trip->hysteresis)) >>>>> tz->trips[trip_id] = *trip; >>>>> >>>>> + if (t.temperature != trip->temperature && tz->governor && tz->governor->reset) { >>>>> + ret = tz->governor->reset(tz, trip_id); >>>>> + if (ret) >>>>> + pr_warn_once("Failed to reset thermal governor\n"); >>>> >>>> I'm not really sure if it is useful to print this message here. >>>> >>>> First off, the governors may print more precise diagnostic messages if >>>> they care. >>>> >>>> Second, what is the sysadmin supposed to do in response to this message? >>> >>> In addition to the above, trip point temperatures may be updated in >>> other places too, for instance in response to notifications from >>> platform firmware and IMV this new callback should be also used in >>> those cases. However, in those cases multiple trip points may change >>> at a time and the critical/hot trip point temperatures may be updated >>> too AFAICS. >> >> IIRC the critical/hot trip points are handled differently, not using the >> governors. The governors' 'throttle' callback would be called only >> after we pass the test of 'critical/hot' [1]. > > OK, but is it actually useful to return an error code from the > ->reset() callback when passed a non-passive trip point? It will depend on the governor code. In our case the setup code w.r.t. trip types is quite confusing (to fit into many possible configurations). The non-passive trip point would be only possible to bind when there are not other passive trip points. That's is a really corner case and probably never used on any device. Therefore, IMO we can just bail out in such situation when then someone tries to update such single non-passive trip point (probably not aware what is doing with IPA?). For the rest of the governors - it's up to them what they report in case non-passive trip is updated... > >> What Di is facing is in the issue under the bucket of >> 'handle_non_critical_trips()' when the governor just tries to >> work on stale data - old trip temp. > > Well, fair enough, but what about the other governors? Is this > problem limited to power_allocator? IIUC the core fwk code - non of the governors would be needed to handle the critical/hot trips. For the rest of the trip types I would say it's up to the governor. In our IPA case this stale data is used for power budget estimation - quite fundamental step. Therefore, the reset and start from scratch would make more sense. I think other governors don't try to 'estimate' such abstract power headroom based on temperature - so probably they don't have to even implement the 'reset()' callback (I don't know their logic that well). > >> For the 2nd case IIUC the code, we pass the 'trip.temperature' >> and should be ready for what you said (modification of that value). > > Generally speaking, it needs to be prepared for a simultaneous change > of multiple trip points (including active), in which case it may not > be useful to invoke the ->reset() callback for each of them > individually. Although, that looks more cleaner IMO. Resetting one by one in a temperature order would be easily maintainable, won't be? > > Moreover, Daniel wants trip points to be sorted by temperature > eventually and in that case indices may change overall even on one > trip point update. It's more complicated I think that this $subject, but very useful. > >> Furthermore, the critical/hot situation is handled w/o governor >> assistance, so we should be safe: >> tz->ops->critical(tz) or tz->ops->hot(tz) and not >> tz->governor->throttle(tz, trip) > > That's fine.