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 BCDC6CDB47E for ; Fri, 13 Oct 2023 16:12:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232031AbjJMQMd (ORCPT ); Fri, 13 Oct 2023 12:12:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232597AbjJMQMV (ORCPT ); Fri, 13 Oct 2023 12:12:21 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e5ab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BF63E103; Fri, 13 Oct 2023 09:11:38 -0700 (PDT) Received: from notapiano (zone.collabora.co.uk [167.235.23.81]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: nfraprado) by madras.collabora.co.uk (Postfix) with ESMTPSA id D81AD6607362; Fri, 13 Oct 2023 17:10:58 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1697213460; bh=N/d1KDLrzpfGVy44YM7QBFJuquGjOyuZ7mvw9nlm5es=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZDoLUXrJPDPTLoIC0bPU+SJr0nXDOHnvQPidfcqohWOCw914G/zt8Ur6OFDaukEQq IScJENZPA12se6YQJfEYozCixgkw84pjcJ9Z5O7gc36OVYEETNOLO+6Ok6ZPTMfkRk bWy+Rz+RW498IOpP9cE+HXic7gUQ3N0AdpTAyEESyaXKXnZVHCVcS64KccFIsqPAuW inIEN1zZUVY7q5IuxGVXpi3GodZ3m7pdKO2bYi0JLFrZ20stAQek/gt264xJHSJ/mi 3KY5L8Ax0UpuQjDrf+el6qwpmklmCprPxLeyVfqXV5uaw8bo65YIGDh5jq9/X6hHsO 01nEhLn7Lls9g== Date: Fri, 13 Oct 2023 12:10:54 -0400 From: =?utf-8?B?TsOtY29sYXMgRi4gUi4gQS4=?= Prado To: "Rafael J. Wysocki" Cc: AngeloGioacchino Del Regno , Daniel Lezcano , kernel@collabora.com, Amit Kucheria , Caesar Wang , Eduardo Valentin , Javi Merino , Sascha Hauer , Zhang Rui , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH v2] thermal/core: Don't update trip points inside the hysteresis range Message-ID: References: <20230922184425.290894-1-nfraprado@collabora.com> <6627b83b-bee7-a123-d845-cad8523ffb30@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 13, 2023 at 05:27:08PM +0200, Rafael J. Wysocki wrote: > On Mon, Sep 25, 2023 at 9:29 AM AngeloGioacchino Del Regno > wrote: > > > > Il 22/09/23 20:44, Nícolas F. R. A. Prado ha scritto: > > > When searching for the trip points that need to be set, the nearest > > > higher trip point's temperature is used for the high trip, while the > > > nearest lower trip point's temperature minus the hysteresis is used for > > > the low trip. The issue with this logic is that when the current > > > temperature is inside a trip point's hysteresis range, both high and low > > > trips will come from the same trip point. As a consequence instability > > > can still occur like this: > > > * the temperature rises slightly and enters the hysteresis range of a > > > trip point > > > * polling happens and updates the trip points to the hysteresis range > > > * the temperature falls slightly, exiting the hysteresis range, crossing > > > the trip point and triggering an IRQ, the trip points are updated > > > * repeat > > > > > > So even though the current hysteresis implementation prevents > > > instability from happening due to IRQs triggering on the same > > > temperature value, both ways, it doesn't prevent it from happening due > > > to an IRQ on one way and polling on the other. > > > > > > To properly implement a hysteresis behavior, when inside the hysteresis > > > range, don't update the trip points. This way, the previously set trip > > > points will stay in effect, which will in a way remember the previous > > > state (if the temperature signal came from above or below the range) and > > > therefore have the right trip point already set. The exception is if > > > there was no previous trip point set, in which case a previous state > > > doesn't exist, and so it's sensible to allow the hysteresis range as > > > trip points. > > > > > > The following logs show the current behavior when running on a real > > > machine: > > > > > > [ 202.524658] thermal thermal_zone0: new temperature boundaries: -2147483647 < x < 40000 > > > 203.562817: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=36986 temp=37979 > > > [ 203.562845] thermal thermal_zone0: new temperature boundaries: 37000 < x < 40000 > > > 204.176059: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=37979 temp=40028 > > > [ 204.176089] thermal thermal_zone0: new temperature boundaries: 37000 < x < 100000 > > > 205.226813: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=40028 temp=38652 > > > [ 205.226842] thermal thermal_zone0: new temperature boundaries: 37000 < x < 40000 > > > > > > And with this patch applied: > > > > > > [ 184.933415] thermal thermal_zone0: new temperature boundaries: -2147483647 < x < 40000 > > > 185.981182: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=36986 temp=37872 > > > 186.744685: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=37872 temp=40058 > > > [ 186.744716] thermal thermal_zone0: new temperature boundaries: 37000 < x < 100000 > > > 187.773284: thermal_temperature: thermal_zone=vpu0-thermal id=0 temp_prev=40058 temp=38698 > > > > > > Fixes: 060c034a9741 ("thermal: Add support for hardware-tracked trip points") > > > Signed-off-by: Nícolas F. R. A. Prado > > > > Reviewed-by: AngeloGioacchino Del Regno > > > > > > > > --- > > > > > > Changes in v2: > > > - Changed logic as suggested by Rafael > > > - Added log example to commit message > > > - Added fixes tag > > > > > > drivers/thermal/thermal_trip.c | 19 +++++++++++++++++-- > > > 1 file changed, 17 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/thermal/thermal_trip.c b/drivers/thermal/thermal_trip.c > > > index 024e2e365a26..597ac4144e33 100644 > > > --- a/drivers/thermal/thermal_trip.c > > > +++ b/drivers/thermal/thermal_trip.c > > > @@ -55,6 +55,7 @@ void __thermal_zone_set_trips(struct thermal_zone_device *tz) > > > { > > > struct thermal_trip trip; > > > int low = -INT_MAX, high = INT_MAX; > > > + bool same_trip = false; > > > int i, ret; > > > > > > lockdep_assert_held(&tz->lock); > > > @@ -63,6 +64,7 @@ void __thermal_zone_set_trips(struct thermal_zone_device *tz) > > > return; > > > > > > for (i = 0; i < tz->num_trips; i++) { > > > + bool low_set = false; > > > int trip_low; > > > > > > ret = __thermal_zone_get_trip(tz, i , &trip); > > > @@ -71,18 +73,31 @@ void __thermal_zone_set_trips(struct thermal_zone_device *tz) > > > > > > trip_low = trip.temperature - trip.hysteresis; > > > > > > - if (trip_low < tz->temperature && trip_low > low) > > > + if (trip_low < tz->temperature && trip_low > low) { > > > low = trip_low; > > > + low_set = true; > > > + same_trip = false; > > > + } > > > > > > if (trip.temperature > tz->temperature && > > > - trip.temperature < high) > > > + trip.temperature < high) { > > > high = trip.temperature; > > > + same_trip = low_set; > > > + } > > > } > > > > > > /* No need to change trip points */ > > > if (tz->prev_low_trip == low && tz->prev_high_trip == high) > > > return; > > > > > > + /* > > > + * If "high" and "low" are the same, skip the change unless this is the > > > + * first time. > > > + */ > > > + if (same_trip && (tz->prev_low_trip != -INT_MAX || > > > + tz->prev_high_trip != INT_MAX)) > > > + return; > > > + > > > tz->prev_low_trip = low; > > > tz->prev_high_trip = high; > > > > > Applied as 6.7 material, but I added a Co-developed-by tag for myself, > because it has been based on my patch. Sounds good, thanks! I'll add it myself in situations like this in the future. Thanks, Nícolas