linux-kernel - Re: [PATCH] cpufreq: Limit resolving a frequency to policy min/max

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Date: Sat, 24 Feb 2024 20:53:25 +0530
From: Shivnandan Kumar <quic_kshivnan@...cinc.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
CC: Viresh Kumar <viresh.kumar@...aro.org>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <kernel@...cinc.com>,
        <quic_pkondeti@...cinc.com>, <quic_namajain@...cinc.com>,
        <stable@...r.kernel.org>, <quic_rgottimu@...cinc.com>
Subject: Re: [PATCH] cpufreq: Limit resolving a frequency to policy min/max

Hi Rafael,

Thanks for reviewing the change.

On 2/23/2024 12:52 AM, Rafael J. Wysocki wrote:
> On Thu, Feb 22, 2024 at 9:35 AM Shivnandan Kumar
> <quic_kshivnan@...cinc.com> wrote:
>>
>> Resolving a frequency to an efficient one should not transgress policy->max
>> (which can be set for thermal reason) and policy->min. Currently there is
>> possibility where scaling_cur_freq can exceed scaling_max_freq when
>> scaling_max_freq is inefficient frequency. Add additional check to ensure
>> that resolving a frequency will respect policy->min/max.
>>
>> Fixes: 1f39fa0dccff ("cpufreq: Introducing CPUFREQ_RELATION_E")
>> Signed-off-by: Shivnandan Kumar <quic_kshivnan@...cinc.com>
>> ---
>>   include/linux/cpufreq.h | 18 +++++++++++++++++-
>>   1 file changed, 17 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
>> index afda5f24d3dd..42d98b576a36 100644
>> --- a/include/linux/cpufreq.h
>> +++ b/include/linux/cpufreq.h
>> @@ -1021,6 +1021,19 @@ static inline int cpufreq_table_find_index_c(struct cpufreq_policy *policy,
>>                                                     efficiencies);
>>   }
>>
>> +static inline bool cpufreq_table_index_is_in_limits(struct cpufreq_policy *policy,
>> +                                                   int idx)
> 
> This is not really about the index only, but about the frequency at
> that index too, so I'd call the function differently.
> 

ACK

>> +{
>> +       unsigned int freq;
>> +
>> +       if (idx < 0)
>> +               return false;
>> +
>> +       freq = policy->freq_table[idx].frequency;
>> +
>> +       return (freq == clamp_val(freq, policy->min, policy->max));
> 
> Redundant outer parens.
> 

ACK


>> +}
>> +
>>   static inline int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
>>                                                   unsigned int target_freq,
>>                                                   unsigned int relation)
>> @@ -1054,7 +1067,10 @@ static inline int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
>>                  return 0;
>>          }
>>
>> -       if (idx < 0 && efficiencies) {
>> +       /*
>> +        * Limit frequency index to honor policy->min/max
>> +        */
> 
> This comment need not be multi-line.
> 

ACK
I will make the changes in next patch set.

Thanks
Shivnandan

>> +       if (!cpufreq_table_index_is_in_limits(policy, idx) && efficiencies) {
>>                  efficiencies = false;
>>                  goto retry;
>>          }
>> --
> 
> Thanks!