On Fri, Nov 07, 2014 at 06:53:00PM +0000, Neil Roberts wrote: > Previously whenever a primitive is drawn the driver would call > _mesa_check_conditional_render which blocks waiting for the result of the > query to determine whether to render. On Gen7+ there is a bit in the > 3DPRIMITIVE command which can be used to disable the primitive based on the > value of a state bit. This state bit can be set based on whether two registers > have different values using the MI_PREDICATE command. We can load these two > registers with the pixel count values stored in the query begin and end to > implement conditional rendering without stalling. > > Unfortunately these two source registers are not in the whitelist of available > registers in the kernel driver so this needs a kernel patch to work. This > patch uses the command parser version from intel_screen to detect whether to > attempt to set the predicate data registers. > > The predicate enable bit is currently only used for drawing 3D primitives. For > blits, clears, bitmaps, copypixels and drawpixels it still causes a stall. For > most of these it would probably just work to call the new > brw_check_conditional_render function instead of > _mesa_check_conditional_render because they already work in terms of rendering > primitives. However it's a bit trickier for blits because it can use the BLT > ring or the blorp codepath. I think these operations are less useful for > conditional rendering than rendering primitives so it might be best to leave > it for a later patch. > > v2: Use the command parser version to detect whether we can write to the > predicate data registers instead of trying to execute a register load > command. > --- > > Glenn Kennard suggested that instead of trying to send a load register > command to detect whether the predicate source registers can be set we > could just increase the command parser version in the kernel driver > and query that. That seems nicer to me so here is a second version of > the patch to do that. I will post a v2 of the kernel patch too.
Oh, I guess my earlier mail was too late. One issue still is picking the numbers, since you seem to assume here that ver >= 2 means the stuff actually works. But like Ken said the cmd parser in upstream isn't really enabled yet. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
