[Mesa-stable] [PATCH] i965/skl/gt4: Fix URB programming restriction.

[Ben Widawsky]

The comment in the code details the restriction. Thanks to Ken for having a very
helpful conversation with me, and spotting the blurb in the link I sent him :P.

There are still stability problems for me on GT4, but this definitely helps with
some of the failures.

Cc: Kenneth Graunke <kenneth at whitecape.org>
Cc: Jordan Justen <jordan.l.justen at intel.com>
Cc: mesa-stable at lists.freedesktop.org (if the original gt4 patch goes to stable)
---

Sarah, you should check this on KBL.
Cc: Sarah Sharp <sarah.a.sharp at linux.intel.com>
---
 src/mesa/drivers/dri/i965/brw_device_info.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_device_info.c b/src/mesa/drivers/dri/i965/brw_device_info.c
index 2ebc084..6117fd3 100644
--- a/src/mesa/drivers/dri/i965/brw_device_info.c
+++ b/src/mesa/drivers/dri/i965/brw_device_info.c
@@ -337,6 +337,14 @@ static const struct brw_device_info brw_device_info_skl_gt3 = {
 
 static const struct brw_device_info brw_device_info_skl_gt4 = {
    GEN9_FEATURES, .gt = 4,
+   /* From the docs:
+    *   URB is limited to 1008KB due to programming restrictions. This is not a
+    *   restriction of the L3 implementation, but of the FF and other clients.
+    *   Therefore, in a GT4 implementation it is possible for the programmed
+    *   allocation of the L3 data array to provide 3*384KB=1152MB [sic] for URB,
+    *   but only 1008KB of this will be used.
+    */
+   .urb.size = 1008 / 3,
 };
 
 static const struct brw_device_info brw_device_info_bxt = {
-- 
2.6.2