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

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Message-ID: <e04669ee-d547-dbbe-e87b-5d7efa6ee8@os.amperecomputing.com>
Date:   Tue, 15 Aug 2023 13:46:00 -0700 (PDT)
From:   Ilkka Koskinen <ilkka@...amperecomputing.com>
To:     Suzuki K Poulose <suzuki.poulose@....com>
cc:     Ilkka Koskinen <ilkka@...amperecomputing.com>,
        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


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.

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);
>> 
>
>