[Mesa-stable] [PATCH] i965/gen6: Fix HiZ hang in WebGL Google maps

[Chad Versace]

We need to emit depth stall flushes before depth and hiz resolves.
Placing them at the top of blorp's state emission fixes the hang.

Fixes HiZ hang in the new WebGL Google maps on Sandybridge Chrome OS.
Tested by zooming in and out continuously for 2 hours.

This patch is based on
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/8bc07bb70163c3706fb4ba5f980e57dc942f56dd

CC: mesa-stable at lists.freedesktop.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70740
Signed-off-by: Stéphane Marchesin <marcheu at chromium.org>
Signed-off-by: Chad Versace <chad.versace at linux.intel.com>
---
 src/mesa/drivers/dri/i965/gen6_blorp.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/gen6_blorp.cpp b/src/mesa/drivers/dri/i965/gen6_blorp.cpp
index 6a5841f..3a0e7ec 100644
--- a/src/mesa/drivers/dri/i965/gen6_blorp.cpp
+++ b/src/mesa/drivers/dri/i965/gen6_blorp.cpp
@@ -1012,6 +1012,16 @@ gen6_blorp_emit_primitive(struct brw_context *brw,
    ADVANCE_BATCH();
 }
 
+static void
+gen6_emit_hiz_workaround(struct brw_context *brw, enum gen6_hiz_op hiz_op)
+{
+   if (hiz_op == GEN6_HIZ_OP_DEPTH_RESOLVE ||
+       hiz_op == GEN6_HIZ_OP_HIZ_RESOLVE) {
+      brw->batch.need_workaround_flush = true;
+      intel_emit_post_sync_nonzero_flush(brw);
+      intel_emit_depth_stall_flushes(brw);
+   }
+}
 
 /**
  * \brief Execute a blit or render pass operation.
@@ -1034,6 +1044,8 @@ gen6_blorp_exec(struct brw_context *brw,
    uint32_t wm_bind_bo_offset = 0;
 
    uint32_t prog_offset = params->get_wm_prog(brw, &prog_data);
+
+   gen6_emit_hiz_workaround(brw, params->hiz_op);
    gen6_emit_3dstate_multisample(brw, params->dst.num_samples);
    gen6_emit_3dstate_sample_mask(brw,
                                  params->dst.num_samples > 1 ?
-- 
1.8.4