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

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Message-ID: <a23d2d44-1636-2ce1-d469-f6d344db66a1@linaro.org>
Date:   Wed, 17 Feb 2021 10:38:36 -0500
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Amit Daniel Kachhap <amit.kachhap@...il.com>,
        Daniel Lezcano <daniel.lezcano@...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>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        "v5 . 7+" <stable@...r.kernel.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] thermal: cpufreq_cooling: freq_qos_update_request()
 returns < 0 on error



On 2/17/21 12:48 AM, Viresh Kumar wrote:
> 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 :).

It fixes the thermal runaway issue on sdm845 that I had reported. So,

Tested-by: Thara Gopinath<thara.gopinath@...aro.org>

> 
>   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));
> 

-- 
Warm Regards
Thara