Re: [PATCH] drm/panthor: Add DEV_QUERY_TIMESTAMP_INFO dev query

[Mihail Atanassov <mihail.atanassov@arm.com>]

On 08/08/2024 13:24, Mary Guillemard wrote:
>> As it stands, this query has nothing to do with the actual GPU so
>> doesn't really belong here.
>>
>> It'd be more valuable, and can maybe give better calibration results
>> than querying the system timestamp separately in userspace, if you
>> reported all of:
>>   * the system timer value
>>   * the system timer frequency
>>   * the GPU timer value
>>   * the GPU timer frequency (because it _could_ be different in some systems)
>>   * the GPU timer offset
> 
> I see, I missed those registers... I will also fix this on my v2 of my Panfrost series.
> 
>  From my understanding, the GPU timer frequency doesn't have a register
> so I suppose it would be wired to cntfrq_el0 if CONFIG_ARM_ARCH_TIMER is
> set, am I correct?

Barring any HW errata, yes, that's the frequency the GPU timer should 
tick at, too.

> 
> Thanks for the review,
> 
> Mary

-- 
Mihail Atanassov <mihail.atanassov@arm.com>