linux-kernel - Re: [PATCH v5 6/7] arm_pmu: Introduce pmu_irq

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Date:   Thu, 18 Jun 2020 11:51:24 +0100
From:   Alexandru Elisei <alexandru.elisei@....com>
To:     Stephen Boyd <swboyd@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     mark.rutland@....com, Julien Thierry <julien.thierry@....com>,
        maz@...nel.org, Will Deacon <will.deacon@....com>,
        catalin.marinas@....com, will@...nel.org,
        Julien Thierry <julien.thierry.kdev@...il.com>
Subject: Re: [PATCH v5 6/7] arm_pmu: Introduce pmu_irq_ops

Hi,

On 6/17/20 9:23 PM, Stephen Boyd wrote:
> Quoting Alexandru Elisei (2020-06-17 04:38:50)
>> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
>> index df352b334ea7..17e5952d21e4 100644
>> --- a/drivers/perf/arm_pmu.c
>> +++ b/drivers/perf/arm_pmu.c
>> @@ -26,8 +26,46 @@
>>  
>>  #include <asm/irq_regs.h>
>>  
>> +static int armpmu_count_irq_users(const int irq);
>> +
>> +struct pmu_irq_ops {
>> +       void (*enable_pmuirq)(unsigned int irq);
>> +       void (*disable_pmuirq)(unsigned int irq);
>> +       void (*free_pmuirq)(unsigned int irq, int cpu, void __percpu *devid);
> Does 'cpu' need to be signed?

I'm not sure what you mean. The cpu argument comes from
drivers/perf/arm_pmu_platform.c::armpmu_free_irqs -> arpmu_free_irq, where is the
iterator variable used by the macro for_each_cpu. The documentation for the macro
states:

/**
* for_each_cpu - iterate over every cpu in a mask
* @cpu: the (optionally unsigned) integer iterator ^^^^^^^^^^^^^^^^^^^

I could write a patch to convert to an unsigned int, but it seems like unnecessary
churn to me.

>> +};
>> +
>> +static void armpmu_free_pmuirq(unsigned int irq, int cpu, void __percpu *devid)
>> +{
>> +       free_irq(irq, per_cpu_ptr(devid, cpu));
>> +}
>> +
>> +static const struct pmu_irq_ops pmuirq_ops = {
>> +       .enable_pmuirq = enable_irq,
>> +       .disable_pmuirq = disable_irq_nosync,
>> +       .free_pmuirq = armpmu_free_pmuirq
>> +};
>> +
>> +static void armpmu_enable_percpu_pmuirq(unsigned int irq)
>> +{
>> +       enable_percpu_irq(irq, IRQ_TYPE_NONE);
>> +}
>> +
>> +static void armpmu_free_percpu_pmuirq(unsigned int irq, int cpu,
>> +                                  void __percpu *devid)
>> +{
>> +       if (armpmu_count_irq_users(irq) == 1)
>> +               free_percpu_irq(irq, devid);
>> +}
>> +
>> +static const struct pmu_irq_ops percpu_pmuirq_ops = {
>> +       .enable_pmuirq = armpmu_enable_percpu_pmuirq,
>> +       .disable_pmuirq = disable_percpu_irq,
>> +       .free_pmuirq = armpmu_free_percpu_pmuirq
>> +};
>> +
>>  static DEFINE_PER_CPU(struct arm_pmu *, cpu_armpmu);
>>  static DEFINE_PER_CPU(int, cpu_irq);
> Same question as above.

Same situation as above - cpu is the iterator variable for for_each_cpu.

Thanks,
Alex