linux-kernel - [PATCH] thermal: cpufreq_cooling: freq_qos_update

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Date:   Wed, 17 Feb 2021 11:18:58 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Amit Daniel Kachhap <amit.kachhap@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Javi Merino <javi.merino@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Amit Kucheria <amitk@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thara Gopinath <thara.gopinath@...aro.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        "v5 . 7+" <stable@...r.kernel.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] thermal: cpufreq_cooling: freq_qos_update_request() returns < 0 on error

freq_qos_update_request() returns 1 if the effective constraint value
has changed, 0 if the effective constraint value has not changed, or a
negative error code on failures.

The frequency constraints for CPUs can be set by different parts of the
kernel. If the maximum frequency constraint set by other parts of the
kernel are set at a lower value than the one corresponding to cooling
state 0, then we will never be able to cool down the system as
freq_qos_update_request() will keep on returning 0 and we will skip
updating cpufreq_state and thermal pressure.

Fix that by doing the updates even in the case where
freq_qos_update_request() returns 0, as we have effectively set the
constraint to a new value even if the consolidated value of the
actual constraint is unchanged because of external factors.

Cc: v5.7+ <stable@...r.kernel.org> # v5.7+
Reported-by: Thara Gopinath <thara.gopinath@...aro.org>
Fixes: f12e4f66ab6a ("thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping")
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
Hi Guys,

This needs to go in 5.12-rc.

Thara, please give this a try and give your tested-by :).

 drivers/thermal/cpufreq_cooling.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/thermal/cpufreq_cooling.c b/drivers/thermal/cpufreq_cooling.c
index f5af2571f9b7..10af3341e5ea 100644
--- a/drivers/thermal/cpufreq_cooling.c
+++ b/drivers/thermal/cpufreq_cooling.c
@@ -485,7 +485,7 @@ static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
 	frequency = get_state_freq(cpufreq_cdev, state);

 	ret = freq_qos_update_request(&cpufreq_cdev->qos_req, frequency);
-	if (ret > 0) {
+	if (ret >= 0) {
 		cpufreq_cdev->cpufreq_state = state;
 		cpus = cpufreq_cdev->policy->cpus;
 		max_capacity = arch_scale_cpu_capacity(cpumask_first(cpus));
-- 
2.25.0.rc1.19.g042ed3e048af