[Mesa-dev] [PATCH v2 2/2] intel/isl: Avoid tiling some 16K-wide render targets

[Nanley Chery]

Fix rendering issues on BDW and SKL.

Fixes 0288fe8d0417730bdd5b3477130dd1dc32bdbcd3
("i965/miptree: Use the correct BLT pitch")

Fixes the following regressions seen

exclusively on SKL:
* KHR-GL46.texture_barrier_ARB.disjoint-texels
* KHR-GL46.texture_barrier_ARB.overlapping-texels
* KHR-GL46.texture_barrier.disjoint-texels
* KHR-GL46.texture_barrier.overlapping-texels

and both on BDW and SKL:
* GTF-GL46.gtf21.GL2FixedTests.buffer_corners.buffer_corners
* GTF-GL46.gtf21.GL2FixedTests.stencil_plane_corners.stencil_plane_corners

v2: Note the fixed tests (Andres).
    Don't cause failures with multisampled surfaces (Andres).
    Don't hamper SKL GT4 (Ken).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107359
Cc: <mesa-stable at lists.freedesktop.org>
---
 src/intel/isl/isl_gen7.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/intel/isl/isl_gen7.c b/src/intel/isl/isl_gen7.c
index 4fa9851233f..a9db21fba52 100644
--- a/src/intel/isl/isl_gen7.c
+++ b/src/intel/isl/isl_gen7.c
@@ -294,6 +294,29 @@ isl_gen6_filter_tiling(const struct isl_device *dev,
     */
    if (ISL_DEV_GEN(dev) < 7 && isl_format_get_layout(info->format)->bpb >= 128)
       *flags &= ~ISL_TILING_Y0_BIT;
+
+   /* From the BDW and SKL PRMs, Volume 2d,
+    * RENDER_SURFACE_STATE::Width - Programming Notes:
+    *
+    *   A known issue exists if a primitive is rendered to the first 2 rows and
+    *   last 2 columns of a 16K width surface. If any geometry is drawn inside
+    *   this square it will be copied to column X=2 and X=3 (arrangement on Y
+    *   position will stay the same). If any geometry exceeds the boundaries of
+    *   this 2x2 region it will be drawn normally. The issue also only occurs
+    *   if the surface has TileMode != Linear.
+    *
+    * [Internal documentation notes that this issue isn't present on SKL GT4.]
+    * To prevent this rendering corruption, only allow linear tiling for
+    * surfaces with widths greater than 16K-2 pixels.
+    *
+    * TODO: Is this an issue for multisampled surfaces as well?
+    */
+   if (info->width > 16382 && info->samples == 1 &&
+       info->usage & ISL_SURF_USAGE_RENDER_TARGET_BIT &&
+       (ISL_DEV_GEN(dev) == 8 ||
+        (dev->info->is_skylake && dev->info->gt != 4))) {
+          *flags &= ISL_TILING_LINEAR_BIT;
+   }
 }
 
 void
-- 
2.18.0