[Intel-gfx] TIMESTAMP register

Daniel Vetter daniel at ffwll.ch
Tue Apr 17 23:04:18 CEST 2012

On Tue, Apr 17, 2012 at 08:34:11PM +0000, Lawrynowicz, Jacek wrote:
> ARB_timer_query allows client read TIMESTAMP both asynchronously and synchronously.
> The former can be implemented as you said but the latter requires support from the KMD.
> This must be a simple MMIO read as this is the only way to report "current" GPU time.
> Implementing synchronous TIMESTAMP query using pipe control would render the third example from ARB_timer_query spec useless.

Ok, I've looked like a dofus again, but now I've read the spec and we
indeed seem to need a synchronous readout of the TIMESTAMP register. I
guess a new register will do, together with some fixed-point integer that
tells userspace how to convert it to nanoseconds.
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48

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