linux-kernel - [PATCH] thermal: gov_power_allocator: Allow binding without cooling devices

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Message-Id: <20240321-gpa-no-cooling-devs-v1-1-5c9e0ef2062e@trvn.ru>
Date: Thu, 21 Mar 2024 19:44:13 +0500
From: Nikita Travkin <nikita@...n.ru>
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 <nikita@...n.ru>
Subject: [PATCH] thermal: gov_power_allocator: Allow binding without
 cooling devices

Commit e83747c2f8e3 ("thermal: gov_power_allocator: Set up trip points earlier")
added a check that would fail binding the governer if there is no
cooling devices bound to the thermal zone. Unfortunately this causes
issues in cases when the TZ is bound to the governer before the cooling
devices are attached to it. (I.e. when the tz is registered using
thermal_zone_device_register_with_trips().)

Additionally, the documentation across gov_power_allocator suggests it's
intended to allow it to be bound to thermal zones without cooling
devices (and thus without passive/active trip points), however the same
change added a check for the trip point to be present, causing those TZ
to fail probing.

Those changes cause all thermal zones to fail on some devices (such as
sc7180-acer-aspire1) and prevent the kernel from controlling the cpu/gpu
frequency based on the temperature, as well as losing all the other
"informational" thermal zones if power_allocator is set as default.

This commit partially reverts the referenced one by dropping the trip
point check and by allowing the TZ to probe even if no actor buffer was
allocated to allow those TZ to probe again.

Fixes: e83747c2f8e3 ("thermal: gov_power_allocator: Set up trip points earlier")
Signed-off-by: Nikita Travkin <nikita@...n.ru>
---
I've noticed that all thermal zones fail probing with -EINVAL on my
sc7180 based Acer Aspire 1 since 6.8. This commit allows me to bring
them back.
---
 drivers/thermal/gov_power_allocator.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
index 1b17dc4c219c..4f2d7f3b7508 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) {
@@ -693,7 +688,7 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
 	}

 	ret = allocate_actors_buffer(params, ret);
-	if (ret) {
+	if (ret && ret != -EINVAL) {
 		dev_warn(&tz->device, "power_allocator: allocation failed\n");
 		kfree(params);
 		return ret;
@@ -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);

---
base-commit: e7528c088874326d3060a46f572252be43755a86
change-id: 20240321-gpa-no-cooling-devs-c79ee3288325

Best regards,
-- 
Nikita Travkin <nikita@...n.ru>