linux-kernel - Re: [PATCH v6 2/8] arm: parse cpu capacity-dmips-mhz from DT

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Date:   Thu, 1 Sep 2016 10:22:31 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Juri Lelli <juri.lelli@....com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        LAK <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King - ARM Linux <linux@....linux.org.uk>,
        Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v6 2/8] arm: parse cpu capacity-dmips-mhz from DT

On 31 August 2016 at 19:08, Juri Lelli <juri.lelli@....com> wrote:
> On 31/08/16 10:14, Vincent Guittot wrote:
>> On 30 August 2016 at 18:28, Juri Lelli <juri.lelli@....com> wrote:
>> > Hi Vincent,
>> >
>> > On 16/08/16 10:20, Vincent Guittot wrote:
>> >> Hi Juri,
>> >>
>> >>
>> >> On 19 July 2016 at 14:40, Juri Lelli <juri.lelli@....com> wrote:
>> >
>> > [...]
>> >
>> >> > +static int
>> >> > +init_cpu_capacity_callback(struct notifier_block *nb,
>> >> > +                          unsigned long val,
>> >> > +                          void *data)
>> >> > +{
>> >> > +       struct cpufreq_policy *policy = data;
>> >> > +       int cpu;
>> >> > +
>> >> > +       if (cap_parsing_failed || cap_parsing_done)
>> >> > +               return 0;
>> >> > +
>> >> > +       switch (val) {
>> >> > +       case CPUFREQ_NOTIFY:
>> >> > +               pr_debug("cpu_capacity: init cpu capacity for CPUs [%*pbl] (to_visit=%*pbl)\n",
>> >> > +                               cpumask_pr_args(policy->related_cpus),
>> >> > +                               cpumask_pr_args(cpus_to_visit));
>> >> > +               cpumask_andnot(cpus_to_visit,
>> >> > +                              cpus_to_visit,
>> >> > +                              policy->related_cpus);
>> >> > +               for_each_cpu(cpu, policy->related_cpus) {
>> >> > +                       raw_capacity[cpu] = arch_scale_cpu_capacity(NULL, cpu) *
>> >> > +                                           policy->max / 1000UL;
>> >>
>> >> Should it be policy->cpuinfo.max_freq instead of policy->max ?
>> >>
>> >
>> > Right. I'll fix the arm64 bits as well.
>> >
>> >> > +                       capacity_scale = max(raw_capacity[cpu], capacity_scale);
>> >> > +               }
>> >> > +               if (cpumask_empty(cpus_to_visit)) {
>> >> > +                       normalize_cpu_capacity();
>> >> > +                       kfree(raw_capacity);
>> >> > +                       pr_debug("cpu_capacity: parsing done\n");
>> >> > +                       cap_parsing_done = true;
>> >>
>> >> ok so you do that once with the 1st governor that will be registered
>> >> for the CPU. Can't you unregister the notifier then ?
>> >>
>> >
>> > I tried, but the only place I could find to unregister it is from the
>> > callback itself; and it is not possible to do so AFAIK. Suggestions?
>>
>> yes, you're right
>> Can't you queue a work to unregister your callback ?
>
> You mean something like this? I guess I thought it would be much more
> ugly. :)

Yes something like below.

>
> If it looks OK, I'll add the same for arm64 and test it a bit more.
>
> --->8---
>  arch/arm/kernel/topology.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
> index cbc57c287145..672ae22e2768 100644
> --- a/arch/arm/kernel/topology.c
> +++ b/arch/arm/kernel/topology.c
> @@ -215,7 +215,8 @@ static void normalize_cpu_capacity(void)
>
>  #ifdef CONFIG_CPU_FREQ
>  static cpumask_var_t cpus_to_visit;
> -static bool cap_parsing_done;
> +static void parsing_done_workfn(struct work_struct *work);
> +static DECLARE_WORK(parsing_done_work, parsing_done_workfn);
>
>  static int
>  init_cpu_capacity_callback(struct notifier_block *nb,
> @@ -225,7 +226,7 @@ init_cpu_capacity_callback(struct notifier_block *nb,
>         struct cpufreq_policy *policy = data;
>         int cpu;
>
> -       if (cap_parsing_failed || cap_parsing_done)
> +       if (cap_parsing_failed)

you probably need to keep cap_parsing_done to prevent spurious
notification until the work is scheduled

>                 return 0;
>
>         switch (val) {
> @@ -245,7 +246,7 @@ init_cpu_capacity_callback(struct notifier_block *nb,
>                         normalize_cpu_capacity();
>                         kfree(raw_capacity);
>                         pr_debug("cpu_capacity: parsing done\n");
> -                       cap_parsing_done = true;
> +                       schedule_work(&parsing_done_work);
>                 }
>         }
>         return 0;
> @@ -270,6 +271,13 @@ static int __init register_cpufreq_notifier(void)
>                                          CPUFREQ_POLICY_NOTIFIER);
>  }
>  core_initcall(register_cpufreq_notifier);
> +
> +static void parsing_done_workfn(struct work_struct *work)
> +{
> +       cpufreq_unregister_notifier(&init_cpu_capacity_notifier,
> +                                        CPUFREQ_POLICY_NOTIFIER);
> +}
> +
>  #else
>  static int __init free_raw_capacity(void)
>  {