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References: <20240319080153.3263-1-xuewen.yan@unisoc.com> <20240320032056.2noz6lu3k2utcpid@vireshk-i7>
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From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: Wed, 27 Mar 2024 16:21:00 +0100
Message-ID: <CAJZ5v0hy=Ak1JynF2fuQ74GNRAQt-mWqnrM+tsJvoU2jgY3FoQ@mail.gmail.com>
Subject: Re: [PATCH] cpufreq: Use a smaller freq for the policy->max when verify
To: Viresh Kumar <viresh.kumar@linaro.org>, Xuewen Yan <xuewen.yan@unisoc.com>
Cc: ke.wang@unisoc.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, 
	xuewen.yan94@gmail.com, di.shen@unisoc.com
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On Wed, Mar 20, 2024 at 4:21=E2=80=AFAM Viresh Kumar <viresh.kumar@linaro.o=
rg> wrote:
>
> On 19-03-24, 16:01, Xuewen Yan wrote:
> > When driver use the cpufreq_frequency_table_verify() as the
> > cpufreq_driver->verify's callback. It may cause the policy->max
> > bigger than the freq_qos's max freq.
> >
> > Just as follow:
> >
> > unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_available_=
frequencies
> > 614400 768000 988000 1228800 1469000 1586000 1690000 1833000 2002000 20=
93000
> >
> > unisoc:/sys/devices/system/cpu/cpufreq/policy0 # echo 1900000 > scaling=
_max_freq
> > unisoc:/sys/devices/system/cpu/cpufreq/policy0 # echo 1900000 > scaling=
_min_freq
> > unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_max_freq
> > 2002000
> > unisoc:/sys/devices/system/cpu/cpufreq/policy0 # cat scaling_min_freq
> > 2002000
> >
> > When user set the qos_min and qos_max as the same value, and the value
> > is not in the freq-table, the above scenario will occur.
> >
> > This is because in cpufreq_frequency_table_verify() func, when it can n=
ot
> > find the freq in table, it will change the policy->max to be a bigger f=
req,
> > as above, because there is no 1.9G in the freq-table, the policy->max w=
ould
> > be set to 2.002G. As a result, the cpufreq_policy->max is bigger than t=
he
> > user's qos_max. This is unreasonable.
> >
> > So use a smaller freq when can not find the freq in fre-table, to preve=
nt
>
>                                                       freq-table
>
> > the policy->max exceed the qos's max freq.
> >
> > Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
> > ---
> >  drivers/cpufreq/freq_table.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

Applied as 6.10 material, thanks!