It turns out that cpuX will stay on the base frequency after performing
these operations:

1. boost all cpus: echo 1 > /sys/devices/system/cpu/cpufreq/boost

2. offline the cpu: echo 0 > /sys/devices/system/cpu/cpuX/online

3. deboost all cpus: echo 0 > /sys/devices/system/cpu/cpufreq/boost

4. online the cpu: echo 1 > /sys/devices/system/cpu/cpuX/online

5. boost all cpus again: echo 1 > /sys/devices/system/cpu/cpufreq/boost

This is because max_freq_req of the policy is not updated during the online
process, and the value of max_freq_req before the last offline is retained.
When the CPU is boosted again, freq_qos_update_request() will do nothing
because the old value is the same as the new one. This causes the CPU stay
on the base frequency. Update max_freq_req  in cpufreq_online() will solve
this problem.

Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
---
 drivers/cpufreq/cpufreq.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 1a4cae54a01b..5882d7f5e3c1 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1475,6 +1475,10 @@ static int cpufreq_online(unsigned int cpu)
 
 		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()) {
-- 
2.33.0

On 17-01-25, 18:14, Lifeng Zheng wrote:
> It turns out that cpuX will stay on the base frequency after performing
> these operations:
> 
> 1. boost all cpus: echo 1 > /sys/devices/system/cpu/cpufreq/boost
> 
> 2. offline the cpu: echo 0 > /sys/devices/system/cpu/cpuX/online
> 
> 3. deboost all cpus: echo 0 > /sys/devices/system/cpu/cpufreq/boost
> 
> 4. online the cpu: echo 1 > /sys/devices/system/cpu/cpuX/online
> 
> 5. boost all cpus again: echo 1 > /sys/devices/system/cpu/cpufreq/boost
> 
> This is because max_freq_req of the policy is not updated during the online
> process, and the value of max_freq_req before the last offline is retained.
> When the CPU is boosted again, freq_qos_update_request() will do nothing
> because the old value is the same as the new one. This causes the CPU stay
> on the base frequency. Update max_freq_req  in cpufreq_online() will solve
> this problem.
> 
> Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
> ---
>  drivers/cpufreq/cpufreq.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 1a4cae54a01b..5882d7f5e3c1 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1475,6 +1475,10 @@ static int cpufreq_online(unsigned int cpu)
>  
>  		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;
>  	}

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh

Hi,

I am bit confused by the sequence of events here and need some
clarification. Lets assume that CPU can go from 1 GHz to 1.5 GHz
without boost enabled and with boost it can go to 2 GHz.

On 17-01-25, 18:14, Lifeng Zheng wrote:
> It turns out that cpuX will stay on the base frequency after performing
> these operations:
> 
> 1. boost all cpus: echo 1 > /sys/devices/system/cpu/cpufreq/boost

Boost enabled here, max_freq_req = 2 GHz.

> 2. offline the cpu: echo 0 > /sys/devices/system/cpu/cpuX/online
> 
> 3. deboost all cpus: echo 0 > /sys/devices/system/cpu/cpufreq/boost
> 
> 4. online the cpu: echo 1 > /sys/devices/system/cpu/cpuX/online

Boost is disabled currently here, but max_freq_req = 2 GHz, which is
incorrect and the current change you are proposing fixes it I think.
But it is not what you are claiming to fix.

> 5. boost all cpus again: echo 1 > /sys/devices/system/cpu/cpufreq/boost

Boost enabled again here, and max_freq_req = 2 GHz is the correct
value.

So the CPU doesn't stay at base frequency here, but 2 GHz only.

> This is because max_freq_req of the policy is not updated during the online
> process, and the value of max_freq_req before the last offline is retained.

which was 2 GHz in your example.

> When the CPU is boosted again, freq_qos_update_request() will do nothing
> because the old value is the same as the new one. This causes the CPU stay
> on the base frequency. Update max_freq_req  in cpufreq_online() will solve
> this problem.

-- 
viresh

On 2025/1/20 16:27, Viresh Kumar wrote:

> Hi,
> 
> I am bit confused by the sequence of events here and need some
> clarification. Lets assume that CPU can go from 1 GHz to 1.5 GHz
> without boost enabled and with boost it can go to 2 GHz.
> 
> On 17-01-25, 18:14, Lifeng Zheng wrote:
>> It turns out that cpuX will stay on the base frequency after performing
>> these operations:
>>
>> 1. boost all cpus: echo 1 > /sys/devices/system/cpu/cpufreq/boost
> 
> Boost enabled here, max_freq_req = 2 GHz.
> 
>> 2. offline the cpu: echo 0 > /sys/devices/system/cpu/cpuX/online
>>
>> 3. deboost all cpus: echo 0 > /sys/devices/system/cpu/cpufreq/boost
>>
>> 4. online the cpu: echo 1 > /sys/devices/system/cpu/cpuX/online
> 
> Boost is disabled currently here, but max_freq_req = 2 GHz, which is
> incorrect and the current change you are proposing fixes it I think.
> But it is not what you are claiming to fix.

Since boost is disabled, policy->max and policy->cpuinfo.max_freq will be
1.5GHz, this limits the actual frequency of the final.

> 
>> 5. boost all cpus again: echo 1 > /sys/devices/system/cpu/cpufreq/boost
> 
> Boost enabled again here, and max_freq_req = 2 GHz is the correct
> value.

In freq_qos_update_request(), if req->pnode.prio == new_value, it will
directly return 0 and not excecute freq_qos_apply(), in which will refresh
frequency. So the frequency will stay on base.

> 
> So the CPU doesn't stay at base frequency here, but 2 GHz only.
> 
>> This is because max_freq_req of the policy is not updated during the online
>> process, and the value of max_freq_req before the last offline is retained.
> 
> which was 2 GHz in your example.
> 
>> When the CPU is boosted again, freq_qos_update_request() will do nothing
>> because the old value is the same as the new one. This causes the CPU stay
>> on the base frequency. Update max_freq_req  in cpufreq_online() will solve
>> this problem.
>

On 20-01-25, 17:10, zhenglifeng (A) wrote:
> On 2025/1/20 16:27, Viresh Kumar wrote:
> > On 17-01-25, 18:14, Lifeng Zheng wrote:
> >> 1. boost all cpus: echo 1 > /sys/devices/system/cpu/cpufreq/boost
> > 
> > Boost enabled here, max_freq_req = 2 GHz.
> > 
> >> 2. offline the cpu: echo 0 > /sys/devices/system/cpu/cpuX/online
> >>
> >> 3. deboost all cpus: echo 0 > /sys/devices/system/cpu/cpufreq/boost
> >>
> >> 4. online the cpu: echo 1 > /sys/devices/system/cpu/cpuX/online
> > 
> > Boost is disabled currently here, but max_freq_req = 2 GHz, which is
> > incorrect and the current change you are proposing fixes it I think.
> > But it is not what you are claiming to fix.
> 
> Since boost is disabled, policy->max and policy->cpuinfo.max_freq will be
> 1.5GHz, this limits the actual frequency of the final.

Okay, I was thinking about the case (!new_policy &&
cpufreq_driver->online), where cpufreq_table_validate_and_sort() isn't
called and max_freq isn't updated eventually. But for the other case,
we will see max-freq as 1.5GHz.

> >> 5. boost all cpus again: echo 1 > /sys/devices/system/cpu/cpufreq/boost
> > 
> > Boost enabled again here, and max_freq_req = 2 GHz is the correct
> > value.
> 
> In freq_qos_update_request(), if req->pnode.prio == new_value, it will
> directly return 0 and not excecute freq_qos_apply(), in which will refresh
> frequency. So the frequency will stay on base.

-- 
viresh