linux-kernel - Re: [PATCH v2 2/2] intel_pstate: Set core to min P state during core offline

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Message-ID: <CAOh2x=kFC5cwdYVgFCwNgqZAwWaE-CFQoyYizBuv1W6MOnQ9DA@mail.gmail.com>
Date:	Tue, 18 Mar 2014 11:14:12 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Dirk Brandewie <dirk.brandewie@...il.com>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Patrick Marlier <patrick.marlier@...il.com>,
	Dirk Brandewie <dirk.j.brandewie@...el.com>
Subject: Re: [PATCH v2 2/2] intel_pstate: Set core to min P state during core offline

On Sat, Mar 15, 2014 at 2:33 AM,  <dirk.brandewie@...il.com> wrote:
> From: Dirk Brandewie <dirk.j.brandewie@...el.com>
>
> Change to use ->stop() callback to do clean up during CPU
> hotplug. The requested P state for an offline core will be used by the
> hardware coordination function to select the package P state. If the
> core is under load when it is offlined it will fix the package P state
> floor to the requested P state of offline core.
>
> Reported-by: Patrick Marlier <patrick.marlier@...il.com>
> Signed-off-by: Dirk Brandewie <dirk.j.brandewie@...el.com>
> ---
>  drivers/cpufreq/intel_pstate.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index 2cd36b9..e9092fd 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -447,7 +447,7 @@ static void core_set_pstate(struct cpudata *cpudata, int pstate)
>         if (limits.no_turbo)
>                 val |= (u64)1 << 32;
>
> -       wrmsrl(MSR_IA32_PERF_CTL, val);
> +       wrmsrl_on_cpu(cpudata->cpu, MSR_IA32_PERF_CTL, val);
>  }
>
>  static struct cpu_defaults core_params = {
> @@ -773,16 +773,22 @@ static int intel_pstate_verify_policy(struct cpufreq_policy *policy)
>         return 0;
>  }
>
> -static int intel_pstate_cpu_exit(struct cpufreq_policy *policy)
> +static int intel_pstate_cpu_stop(struct cpufreq_policy *policy)
>  {
> -       int cpu = policy->cpu;
> +       int cpu_num = policy->cpu;
> +       struct cpudata *cpu = all_cpu_data[cpu_num];
> +
> +       pr_info("intel_pstate CPU %d exiting\n", cpu_num);
> +
> +       del_timer(&all_cpu_data[cpu_num]->timer);
> +       intel_pstate_set_pstate(cpu, cpu->pstate.min_pstate);
> +       kfree(all_cpu_data[cpu_num]);
> +       all_cpu_data[cpu_num] = NULL;
>
> -       del_timer(&all_cpu_data[cpu]->timer);
> -       kfree(all_cpu_data[cpu]);
> -       all_cpu_data[cpu] = NULL;
>         return 0;
>  }
>
> +
>  static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
>  {
>         struct cpudata *cpu;
> @@ -818,7 +824,7 @@ static struct cpufreq_driver intel_pstate_driver = {
>         .setpolicy      = intel_pstate_set_policy,
>         .get            = intel_pstate_get,
>         .init           = intel_pstate_cpu_init,
> -       .exit           = intel_pstate_cpu_exit,
> +       .stop           = intel_pstate_cpu_stop,

Probably, keep exit as is and only change P-state in stop(). So that
allocation of resources happen in init() and they are freed in exit()?
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