[Intel-gfx] Valleyview: 3DSTATE_URB_VS Minimum URB Entries

[Jesse Barnes]

"Cheah, Douglas" <douglas.cheah at intel.com> wrote:

>Hello folks,
>
>I am seeing corruption when running spectex from mesa demos which looks
>like vertex being randomly clipped on Valleyview, however spectex works
>fine on Ivy Bridge.
>
>After tracing down the codes I realize that the current Mesa driver
>would program the maximum number or URB entries (512 Valleyview) 
>whenever possible. This conflict with the 3D pipeline PRM where it
>states there is a programming restriction if the URB Entry Allocation
>Size is less than 9 URB entries then total entries should be program to
>32. After modifying the codes to meet the restriction I was able to run
>spectex without corruption on Valleyview, pretty surprise that Ivy
>Bridge did not have this problem.
>
>Here is the code snippet that I have changed which is at this point a
>quick hack and not upstream worthy as you can see the macro is not even
>properly defined in brw_defeines.h. Appreciate if I could get opinions
>from folks who are more familiar with Mesa and more experience with the
>graphic core.
>
>
>static void
>gen7_upload_urb(struct brw_context *brw)
>{
>   struct intel_context *intel = &brw->intel;
>   /* Total space for entries is URB size - 16kB for push constants */
>   int handle_region_size = (brw->urb.size - 16) * 1024; /* bytes */
>
>   /* CACHE_NEW_VS_PROG */
>   brw->urb.vs_size = MAX2(brw->vs.prog_data->urb_entry_size, 1);
>
>   int nr_vs_entries = handle_region_size / (brw->urb.vs_size * 64);
>   if (nr_vs_entries > brw->urb.max_vs_entries)
>      nr_vs_entries = brw->urb.max_vs_entries;
>
>   /* If the number of URB Allocation Size is smaller than 9 512 bit
>    * units set the number or URB to Entries to 32
>    */
>#define GEN7_URB_VS_MIN_ENTRIES 32
>   if(brw->urb.vs_size < 9)
>        nr_vs_entries = GEN7_URB_VS_MIN_ENTRIES;
>
>
>
>Douglas
>_______________________________________________
>Intel-gfx mailing list
>Intel-gfx at lists.freedesktop.org
>http://lists.freedesktop.org/mailman/listinfo/intel-gfx

ooh this is a good fix. Can you bounce it over to the meas list for inclusion? 
-- 
Jesse Barnes, Intel Open Source Technology Center