linux-kernel - [PATCH v2 2/3] thermal: gov_power_allocator: Allow binding without trip points

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Message-Id: <20240403-gpa-no-cooling-devs-v2-2-79bdd8439449@trvn.ru>
Date: Wed, 03 Apr 2024 16:31:41 +0500
From: Nikita Travkin via B4 Relay <devnull+nikita.trvn.ru@...nel.org>
To: Lukasz Luba <lukasz.luba@....com>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, 
 Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, 
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Nikita Travkin <nikitos.tr@...il.com>, Nikita Travkin <nikita@...n.ru>
Subject: [PATCH v2 2/3] thermal: gov_power_allocator: Allow binding without
 trip points

From: Nikita Travkin <nikita@...n.ru>

IPA probe function was recently refactored to perform extra error checks
and make sure the thermal zone has trip points necessary for the IPA
operation. With this change, if a thermal zone is probed such that it
has no trip points that IPA can use, IPA will fail and the TZ won't be
created. This is the case if a platform defines a TZ without cooling
devices and only with "hot"/"critical" trip points, often found on some
Qualcomm devices [1].

Documentation across IPA code (notably get_governor_trips() kerneldoc)
suggests that IPA is supposed to handle such TZ even if it won't
actually do anything.

This commit partially reverts the previous change to allow IPA to bind
to such "empty" thermal zones.

[1] arch/arm64/boot/dts/qcom/sc7180.dtsi#n4776

Fixes: e83747c2f8e3 ("thermal: gov_power_allocator: Set up trip points earlier")
Signed-off-by: Nikita Travkin <nikita@...n.ru>
---
 drivers/thermal/gov_power_allocator.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
index ec637071ef1f..e25e48d76aa7 100644
--- a/drivers/thermal/gov_power_allocator.c
+++ b/drivers/thermal/gov_power_allocator.c
@@ -679,11 +679,6 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
 		return -ENOMEM;

 	get_governor_trips(tz, params);
-	if (!params->trip_max) {
-		dev_warn(&tz->device, "power_allocator: missing trip_max\n");
-		kfree(params);
-		return -EINVAL;
-	}

 	ret = check_power_actors(tz, params);
 	if (ret < 0) {
@@ -714,9 +709,10 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
 	else
 		params->sustainable_power = tz->tzp->sustainable_power;

-	estimate_pid_constants(tz, tz->tzp->sustainable_power,
-			       params->trip_switch_on,
-			       params->trip_max->temperature);
+	if (params->trip_max)
+		estimate_pid_constants(tz, tz->tzp->sustainable_power,
+				       params->trip_switch_on,
+				       params->trip_max->temperature);

 	reset_pid_controller(params);

-- 
2.44.0