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.
Regards, Jacek -----Original Message----- From: Daniel Vetter [mailto:[email protected]] On Behalf Of Daniel Vetter Sent: Tuesday, April 17, 2012 9:40 PM To: Lawrynowicz, Jacek Cc: [email protected] Subject: Re: [Intel-gfx] TIMESTAMP register On Tue, Apr 17, 2012 at 07:12:40PM +0000, Lawrynowicz, Jacek wrote: > Starting from IVB the main TIMESTAMP register is longer than 32 bits > (it’s 36 bits long). > > How should we pass its 36 bit value from i915 to user space? > > GET_PARAM ioctls supports only 32 bit params. Should we add > GET_PARAM64 or create separate ioctl to access the TIMESTAMP? > > Any suggestions? > > > > This functionality is required for any OpenGL driver which implements > GL_ARB_timer_query. Like occlusion queries I presume this should be done with a pipe control qword write issued from a batch. GETPARAM makes absolutely no sense, that is for driver features, not hw features and just used so that a new driver also can work on an older kernel. -Daniel -- Daniel Vetter Mail: [email protected] Mobile: +41 (0)79 365 57 48
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