Re: [PATCH v5 1/6] cpufreq: Remove per-CPU QoS constraint

["zhenglifeng (A)" <zhenglifeng1@huawei.com>]

On 3/16/2026 10:45 PM, Pierre Gondois wrote:
> 
> On 3/13/26 09:57, Viresh Kumar wrote:
>> On 25-02-26, 09:49, Pierre Gondois wrote:
>>> policy->max_freq_req represents the maximum allowed frequency as
>>> requested by the policyX/scaling_max_freq sysfs file. This request
>>> applies to all CPUs of the policy. It is not possible to request
>>> a per-CPU maximum frequency.
>>>
>>> Thus, the interaction between the policy boost and scaling_max_freq
>>> settings should be handled by adding a boost specific QoS constraint.
>>> This will be handled in the following patches.
>>>
>>> This patch reverts of:
>>> commit 1608f0230510 ("cpufreq: Fix re-boost issue after hotplugging
>>> a CPU")
>>>
>>> Reviewed-by: Lifeng Zheng <zhenglifeng1@huawei.com>
>>> Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
>>> ---
>>>   drivers/cpufreq/cpufreq.c | 4 ----
>>>   1 file changed, 4 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>>> index 4472bb1ec83c7..db414c052658b 100644
>>> --- a/drivers/cpufreq/cpufreq.c
>>> +++ b/drivers/cpufreq/cpufreq.c
>>> @@ -1481,10 +1481,6 @@ static int cpufreq_policy_online(struct cpufreq_policy *policy,
>>>             blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
>>>                   CPUFREQ_CREATE_POLICY, policy);
>>> -    } else {
>>> -        ret = freq_qos_update_request(policy->max_freq_req, policy->max);
>>> -        if (ret < 0)
>>> -            goto out_destroy_policy;
>>>       }
>>>         if (cpufreq_driver->get && has_target()) {
>> Even if this change is required, I don't think this should be applied
>> separately. Just reverting this will get the bug back, which was fixed by
>> commit 1608f0230510. Individual patches shouldn't break kernel (and bisect) as
>> much as possible.
>>
> I could not reproduce the original issue.
> 
> At the time of the patch and still now, calls to
> freq_qos_update_request() are checked against negative values.
> The only exception is when using the scaling_max_frequency sysfs
> entry, but this is out of the scope.
> 
> So I don't see how:
> 
> commit 1608f0230510 ("cpufreq: Fix re-boost issue after hotplugging a CPU")
> 
> can prevent a CPU to reach the boost frequency.  The only path that
> could fail and that I could reproduce was fixed by:
> 
> https://lore.kernel.org/all/852ff11c589e6300730d207baac195b2d9d8b95f.1745511526.git.viresh.kumar@linaro.org/
> 
> So the current conclusion is that "cpufreq: Fix re-boost issue after hotplugging a CPU"
> was not the real fix
> 
> 

Yes. After Viresh's patchset, the original issue was solved. So commit
1608f0230510 is not needed anymore and can be reverted.