linux-kernel - Re: [PATCH v6 1/4] perf: arm_cspmu: Split 64-bit write to 32-bit writes

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Date:   Wed, 16 Aug 2023 15:00:18 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Ilkka Koskinen <ilkka@...amperecomputing.com>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Besar Wicaksono <bwicaksono@...dia.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Corbet <corbet@....net>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v6 1/4] perf: arm_cspmu: Split 64-bit write to 32-bit
 writes

On 15/08/2023 21:46, Ilkka Koskinen wrote:
> 
> Hi Suzuki,
> 
> On Tue, 15 Aug 2023, Suzuki K Poulose wrote:
>> On 15/08/2023 07:35, Ilkka Koskinen wrote:
>>> Split the 64-bit register accesses if 64-bit access is not supported
>>> by the PMU.
>>>
>>> Signed-off-by: Ilkka Koskinen <ilkka@...amperecomputing.com>
>>> Reviewed-by: Besar Wicaksono <bwicaksono@...dia.com>
>>
>> Do we need a Fixes tag ?
> 
> I believe, NVIDIA's PMU supports 64-bit access while Ampere's one 
> doesn't and since this patchset enables support for the latter one, it 
> doesn't seem like we need a Fixes tag here.

Ok, makes sense.

Suzuki


> 
> Cheers, Ilkka
> 
>>
>> With that:
>>
>> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
>>
>> Suzuki
>>
>>> ---
>>>   drivers/perf/arm_cspmu/arm_cspmu.c | 5 ++++-
>>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c 
>>> b/drivers/perf/arm_cspmu/arm_cspmu.c
>>> index 04be94b4aa48..6387cbad7a7d 100644
>>> --- a/drivers/perf/arm_cspmu/arm_cspmu.c
>>> +++ b/drivers/perf/arm_cspmu/arm_cspmu.c
>>> @@ -715,7 +715,10 @@ static void arm_cspmu_write_counter(struct 
>>> perf_event *event, u64 val)
>>>       if (use_64b_counter_reg(cspmu)) {
>>>           offset = counter_offset(sizeof(u64), event->hw.idx);
>>>   -        writeq(val, cspmu->base1 + offset);
>>> +        if (cspmu->has_atomic_dword)
>>> +            writeq(val, cspmu->base1 + offset);
>>> +        else
>>> +            lo_hi_writeq(val, cspmu->base1 + offset);
>>
>>
>>>       } else {
>>>           offset = counter_offset(sizeof(u32), event->hw.idx);
>>>
>>
>>