Re: [PATCH v2 1/4] cpufreq: Fix re-boost issue after hotplugging a cpu

From: Viresh Kumar
Date: Mon Jan 20 2025 - 04:21:56 EST


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@xxxxxxxxxx>
> ---
> 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@xxxxxxxxxx>

--
viresh