[Mesa-stable] [PATCH] i965/gen6/blorp: Emit more flushes to workaround hangs

[Chad Versace]

This is a squash of three related cherry-picks from master.

[PATCH 1/3]

  i965/gen6/blorp: Set need_workaround_flush immediately after primitive

  This patch makes the workaround code in gen6 blorp follow the pattern
  established in the regular draw path. It shouldn't result in any
  behavioral change.

  On gen6, there are two places where we emit 3D_CMD_PRIM: brw_emit_prim()
  and gen6_blorp_emit_primitive().  brw_emit_prim() sets
  need_workaround_flush immediately after emitting the primitive, but
  blorp does not. Blorp sets need_workaround_flush at the bottom of
  brw_blorp_exec().

  This patch moves the need_workaround_flush from brw_blorp_exec() to
  gen6_blorp_emit_primitive().  There is no need to set
  need_workaround_flush in gen7_blorp_emit_primitive() because the
  workaround applies only to gen6.

  Reviewed-by: Paul Berry <stereotype441 at gmail.com>
  Signed-off-by: Chad Versace <chad.versace at linux.intel.com>
  (cherry picked from commit 5e0cd58de4261e9dca7a15037192e7e9426a0207)

[PATCH 2/3]

  i965/gen6/blorp: Set need_workaround_flush at top of blorp

  Unconditionally set brw->need_workaround_flush at the top of gen6 blorp
  state emission.

  The art of emitting workaround flushes on Sandybridge is mysterious and
  not fully understood. Ken and I believe that
  intel_emit_post_sync_nonzero_flush() may be required when switching from
  regular drawing to blorp.  This is an extra safety measure to prevent
  undiscovered difficult-to-diagnose gpu hangs.

  I verified that on ChromeOS, pre-patch, need_workaround_flush was not
  set at the top of blorp, as Paul expected. To verify, I inserted the
  following debug code at the top of gen6_blorp_exec(), restarted the ui,
  and inspected the logs in /var/log/ui. The abort gets triggered so early
  that the browser never appears on the display.

      static void
      gen6_blorp_exec(...)
      {
          if (!brw->need_workaround_flush) {
              fprintf(stderr, "chadv: %s:%d\n", __FILE__, __LINE__);
              abort();
          }
          ...
      }

  CC: Kenneth Graunke <kenneth at whitecape.org>
  CC: Stéphane Marchesin <marcheu at chromium.org>
  Reviewed-by: Paul Berry <stereotype441 at gmail.com>
  Signed-off-by: Chad Versace <chad.versace at linux.intel.com>
  (cherry picked from commit 6a5c86f48675d2ca0975d69e0899e72afaab29e5)

[PATCH 3/3]

  i965/gen6/blorp: Remove redundant HiZ workaround

  Commit 1a92881 added extra flushes to fix a HiZ hang in
  WebGL Google Maps. With the extra flushes emitted by the previous two
  patches, the flushes added by 1a92881 are redundant.

  Tested with the same criteria as in 1a92881: by zooming in and out
  continuously for 2 hours on Sandybridge Chrome OS (codename
  Stumpy) without a hang.

  CC: Kenneth Graunke <kenneth at whitecape.org>
  CC: Stéphane Marchesin <marcheu at chromium.org>
  Reviewed-by: Paul Berry <stereotype441 at gmail.com>
  Signed-off-by: Chad Versace <chad.versace at linux.intel.com>
  (cherry picked from commit 90368875e733171350c64c8dda52f81bd0705dd0)

  Conflicts:
  	src/mesa/drivers/dri/i965/gen6_blorp.cpp
---
 src/mesa/drivers/dri/i965/brw_blorp.cpp  |  1 -
 src/mesa/drivers/dri/i965/gen6_blorp.cpp | 19 +++++--------------
 2 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_blorp.cpp b/src/mesa/drivers/dri/i965/brw_blorp.cpp
index fda86f8..13839e8 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp.cpp
@@ -266,7 +266,6 @@ retry:
     */
    brw->state.dirty.brw = ~0;
    brw->state.dirty.cache = ~0;
-   brw->batch.need_workaround_flush = true;
    brw->ib.type = -1;
    intel_batchbuffer_clear_cache(brw);
 
diff --git a/src/mesa/drivers/dri/i965/gen6_blorp.cpp b/src/mesa/drivers/dri/i965/gen6_blorp.cpp
index ccb09e7..a132234 100644
--- a/src/mesa/drivers/dri/i965/gen6_blorp.cpp
+++ b/src/mesa/drivers/dri/i965/gen6_blorp.cpp
@@ -1010,20 +1010,9 @@ gen6_blorp_emit_primitive(struct brw_context *brw,
    OUT_BATCH(0);
    OUT_BATCH(0);
    ADVANCE_BATCH();
-}
 
-static void
-gen6_emit_hiz_workaround(struct brw_context *brw, enum gen6_hiz_op hiz_op)
-{
-   /* This fixes a HiZ hang in WebGL Google Maps. A more minimal fix likely
-    * exists, but this gets the job done.
-    */
-   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);
-   }
+   /* Only used on Sandybridge; harmless to set elsewhere. */
+   brw->batch.need_workaround_flush = true;
 }
 
 /**
@@ -1048,7 +1037,9 @@ gen6_blorp_exec(struct brw_context *brw,
 
    uint32_t prog_offset = params->get_wm_prog(brw, &prog_data);
 
-   gen6_emit_hiz_workaround(brw, params->hiz_op);
+   /* Emit workaround flushes when we switch from drawing to blorping. */
+   brw->batch.need_workaround_flush = true;
+
    gen6_emit_3dstate_multisample(brw, params->num_samples);
    gen6_emit_3dstate_sample_mask(brw, params->num_samples, 1.0, false, ~0u);
    gen6_blorp_emit_state_base_address(brw, params);
-- 
1.8.5.2