[PATCH v2 5/5] arm64: perf: Add support for chaining event counters

[Suzuki.Poulose@arm.com (Suzuki K Poulose)]

On 11/06/18 15:24, Mark Rutland wrote:
> On Mon, Jun 11, 2018 at 02:54:16PM +0100, Suzuki K Poulose wrote:
>> On 08/06/18 15:46, Suzuki K Poulose wrote:
>>> On 06/06/2018 07:01 PM, Mark Rutland wrote:
>>>> On Tue, May 29, 2018 at 11:55:56AM +0100, Suzuki K Poulose wrote:
>>
>>>>> -??????? value |= 0xffffffff00000000ULL;
>>>>> +??????? if (!armv8pmu_event_is_64bit(event))
>>>>> +??????????? value |= 0xffffffff00000000ULL;
>>>>>  ????????? write_sysreg(value, pmccntr_el0);
>>>>> -??? } else if (armv8pmu_select_counter(idx) == idx)
>>>>> -??????? write_sysreg(value, pmxevcntr_el0);
>>>>> +??? } else
>>>>> +??????? armv8pmu_write_hw_counter(event, value);
>>>>>  ? }
>>>>
>>>>> +static inline void armv8pmu_write_event_type(struct perf_event *event)
>>>>> +{
>>>>> +??? struct hw_perf_event *hwc = &event->hw;
>>>>> +??? int idx = hwc->idx;
>>>>> +
>>>>> +??? /*
>>>>> +???? * For chained events, write the the low counter event type
>>>>> +???? * followed by the high counter. The high counter is programmed
>>>>> +???? * with CHAIN event code with filters set to count at all ELs.
>>>>> +???? */
>>>>> +??? if (armv8pmu_event_is_chained(event)) {
>>>>> +??????? u32 chain_evt = ARMV8_PMUV3_PERFCTR_CHAIN |
>>>>> +??????????????? ARMV8_PMU_INCLUDE_EL2;
>>>>> +
>>>>> +??????? armv8pmu_write_evtype(idx - 1, hwc->config_base);
>>>>> +??????? isb();
>>>>> +??????? armv8pmu_write_evtype(idx, chain_evt);
>>>>
>>>> The ISB isn't necessary here, AFAICT. We only do this while the PMU is
>>>> disabled; no?
>>>
>>> You're right. I was just following the ARM ARM.
>>
>> Taking another look, it is not clear about the semantics of "pmu->enable()"
>> and pmu->disable() callbacks.
> 
> I was talking about pmu::{pmu_disable,pmu_enable}(), so I'm not sure I
> follow how arm_pmu::{enable,disable}() are relevant here.> 
> The arm_pmu::{enable,disable}() callbacks enable or disable individual
> counters. For example, leaving unused counters disabled may save power,
> even if the PMU as a whole is enabled.

Ah, I mistook cpu_pmu->enable/disable for the core pmu ops. My bad.
Sorry about the noise.

Suzuki