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

[Mihail Atanassov]

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@xxxxxxx>