From: Lukasz Luba <lukasz.luba@arm.com>
To: Viresh Kumar <viresh.kumar@linaro.org>, Amit Kucheria <amitk@kernel.org>
Cc: Amit Daniel Kachhap <amit.kachhap@gmail.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Javi Merino <javi.merino@kernel.org>,
Zhang Rui <rui.zhang@intel.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Thara Gopinath <thara.gopinath@linaro.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
"v5 . 7+" <stable@vger.kernel.org>,
linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] thermal: cpufreq_cooling: freq_qos_update_request() returns < 0 on error
Date: Wed, 17 Feb 2021 10:29:13 +0000 [thread overview]
Message-ID: <91749e19-9091-1292-b8aa-c923efa8021d@arm.com> (raw)
In-Reply-To: <b2b7e84944937390256669df5a48ce5abba0c1ef.1613540713.git.viresh.kumar@linaro.org>
Hi Viresh,
On 2/17/21 5:48 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.
To be precised, thermal pressure signal is not so important in this
mechanism and the 'cpufreq_state' has changed recently:
236761f19a4f373354 thermal/drivers/cpufreq_cooling: Update
cpufreq_state only if state has changed
>
> 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@vger.kernel.org> # v5.7+
> Reported-by: Thara Gopinath <thara.gopinath@linaro.org>
> Fixes: f12e4f66ab6a ("thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping")
I'm not sure if that f12e4f is the root cause.
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.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(-)
Anyway, the fix LGTM. I will have to make sure that I'm CC'ed for these
topic, so I can have a look (I missed somehow 236761f19)
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Regards,
Lukasz
next prev parent reply other threads:[~2021-02-17 10:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 5:48 [PATCH] thermal: cpufreq_cooling: freq_qos_update_request() returns < 0 on error Viresh Kumar
2021-02-17 10:29 ` Lukasz Luba [this message]
2021-02-17 10:39 ` Viresh Kumar
2021-02-17 10:45 ` Lukasz Luba
2021-02-17 14:21 ` Rafael J. Wysocki
2021-02-17 15:38 ` Thara Gopinath
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