Re: [PATCH V5 2/2] arm64: perf: add support for percpu pmu interrupt

[Vinayak Kale]

On Tue, Nov 26, 2013 at 12:11 AM, Will Deacon <will.deacon@xxxxxxx> wrote:
> On Mon, Nov 25, 2013 at 09:45:53AM +0000, Vinayak Kale wrote:
>> Add support for irq registration when pmu interrupt is percpu.
>>
>> Signed-off-by: Vinayak Kale <vkale@xxxxxxx>
>> Signed-off-by: Tuan Phan <tphan@xxxxxxx>
>> ---
>>  arch/arm64/kernel/perf_event.c |  108 ++++++++++++++++++++++++++++++----------
>>  1 file changed, 81 insertions(+), 27 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
>> index cea1594..a2efab3 100644
>> --- a/arch/arm64/kernel/perf_event.c
>> +++ b/arch/arm64/kernel/perf_event.c
>> @@ -22,6 +22,7 @@
>>
>>  #include <linux/bitmap.h>
>>  #include <linux/interrupt.h>
>> +#include <linux/irq.h>
>>  #include <linux/kernel.h>
>>  #include <linux/export.h>
>>  #include <linux/perf_event.h>
>> @@ -363,22 +364,55 @@ validate_group(struct perf_event *event)
>>  }
>>
>>  static void
>> +armpmu_disable_percpu_irq(void *data)
>> +{
>> +     struct arm_pmu *armpmu = data;
>> +     struct platform_device *pmu_device = armpmu->plat_device;
>> +     int irq = platform_get_irq(pmu_device, 0);
>> +
>> +     cpumask_test_and_clear_cpu(smp_processor_id(), &armpmu->active_irqs);
>> +     disable_percpu_irq(irq);
>> +}
>> +
>> +static void
>>  armpmu_release_hardware(struct arm_pmu *armpmu)
>>  {
>>       int i, irq, irqs;
>>       struct platform_device *pmu_device = armpmu->plat_device;
>>
>>       irqs = min(pmu_device->num_resources, num_possible_cpus());
>> +     if (irqs < 1)
>
> Can you just make irqs unsigned, then do if (!irqs) instead?

Okay. I will also modify already existing similar check in function
'armpmu_reserve_hardware'.

>
>> +             return;
>>
>> -     for (i = 0; i < irqs; ++i) {
>> -             if (!cpumask_test_and_clear_cpu(i, &armpmu->active_irqs))
>> -                     continue;
>> -             irq = platform_get_irq(pmu_device, i);
>> -             if (irq >= 0)
>> -                     free_irq(irq, armpmu);
>> +     irq = platform_get_irq(pmu_device, 0);
>> +     if (irq <= 0)
>> +             return;
>> +
>> +     if (irq_is_percpu(irq)) {
>> +             on_each_cpu(armpmu_disable_percpu_irq, armpmu, 1);
>> +             free_percpu_irq(irq, &cpu_hw_events);
>> +     } else {
>> +             for (i = 0; i < irqs; ++i) {
>> +                     if (!cpumask_test_and_clear_cpu(i, &armpmu->active_irqs))
>> +                             continue;
>> +                     irq = platform_get_irq(pmu_device, i);
>> +                     if (irq > 0)
>> +                             free_irq(irq, armpmu);
>> +             }
>>       }
>>  }
>>
>> +static void
>> +armpmu_enable_percpu_irq(void *data)
>> +{
>> +     struct arm_pmu *armpmu = data;
>> +     struct platform_device *pmu_device = armpmu->plat_device;
>> +     int irq = platform_get_irq(pmu_device, 0);
>> +
>> +     enable_percpu_irq(irq, 0);
>
> IRQ_TYPE_NONE?

Did you mean to use macro instead or 0? If yes, I will modify.

Or, are you asking why are we using 0? For this part here is my comment:
Inside GIC it's 'implementation specific' whether to allow
configuration of level/edge type for PPIs.
So maybe we should leave it to boot-loader to do such config if any
such explicit config is needed.
Passing 0 (=IRQ_TYPE_NONE) to 'enable_percpu_irq' ensures that kernel
doesn't touch the existing configuration.

I observed that arm arch timer code also passes 0 (IRQ_TYPE_NONE) to
'enable_percpu_irq'.

>
>> +     cpumask_set_cpu(smp_processor_id(), &armpmu->active_irqs);
>> +}
>> +
>>  static int
>>  armpmu_reserve_hardware(struct arm_pmu *armpmu)
>>  {
>> @@ -396,34 +430,54 @@ armpmu_reserve_hardware(struct arm_pmu *armpmu)
>>               return -ENODEV;
>>       }
>>
>> -     for (i = 0; i < irqs; ++i) {
>> -             err = 0;
>> -             irq = platform_get_irq(pmu_device, i);
>> -             if (irq < 0)
>> -                     continue;
>> +     irq = platform_get_irq(pmu_device, 0);
>> +     if (irq <= 0) {
>> +             pr_err("failed to get valid irq for PMU device\n");
>> +             return -ENODEV;
>> +     }
>>
>> -             /*
>> -              * If we have a single PMU interrupt that we can't shift,
>> -              * assume that we're running on a uniprocessor machine and
>> -              * continue. Otherwise, continue without this interrupt.
>> -              */
>> -             if (irq_set_affinity(irq, cpumask_of(i)) && irqs > 1) {
>> -                     pr_warning("unable to set irq affinity (irq=%d, cpu=%u)\n",
>> -                                 irq, i);
>> -                     continue;
>> -             }
>> +     if (irq_is_percpu(irq)) {
>> +             err = request_percpu_irq(irq, armpmu->handle_irq,
>> +                             "arm-pmu", &cpu_hw_events);
>
> This is a bit of a kludge passing in the cpu_hw_events as the per-cpu token,
> but I guess that will do for now. There is potential for something like a
> master-aware L2 PMU which uses PPIs and expects to pass something different
> back to the IRQ handler.
>
> Will
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