[Mesa-stable] [PATCH 1/4] i965: Fall back to GL 4.2 on Haswell if the kernel isn't new enough.

[Kenneth Graunke]

In commit d2590eb65ff28a9cbd592353d15d7e6cbd2c6fc6 I enabled GL 4.5
on Haswell...but failed to check if we could do indirect compute
shader dispatch...and query buffer objects.

Indirect compute shader dispatch requires command parser version 5
(kernel commit 7b9748cb513a6bef4af87b79f0da3ff7e8b56cd8, which is in
Linux v4.4).  On earlier kernels we would have disabled
ARB_compute_shader, which is a mandatory part of OpenGL 4.3+.

Query buffer objects currently require MI_MATH and MI_LOAD_REGISTER_REG,
which mean command parser version 7 (Linux v4.8).  On earlier kernels
we would have disabled ARB_query_buffer_object, which is a mandatory
part of OpenGL 4.3+.

The new version support looks like:

- Kernel 4.1 and older => OpenGL 3.3
- Kernel 4.2-4.7       => OpenGL 4.2
- Kernel 4.8+          => OpenGL 4.5

Cc: "17.0" <mesa-stable at lists.freedesktop.org>
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/intel_screen.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/intel_screen.c b/src/mesa/drivers/dri/i965/intel_screen.c
index 81cb0deabb3..225a387fa90 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.c
+++ b/src/mesa/drivers/dri/i965/intel_screen.c
@@ -1554,8 +1554,13 @@ set_max_gl_versions(struct intel_screen *screen)
       dri_screen->max_gl_es2_version = has_astc ? 32 : 31;
       break;
    case 7:
-      dri_screen->max_gl_core_version = screen->devinfo.is_haswell &&
-         can_do_pipelined_register_writes(screen) ? 45 : 33;
+      dri_screen->max_gl_core_version = 33;
+      if (screen->devinfo.is_haswell &&
+          can_do_pipelined_register_writes(screen) &&
+          can_do_mi_math_and_lrr(screen)) {
+         dri_screen->max_gl_core_version =
+            can_do_compute_dispatch(screen) ? 45 : 42;
+      }
       dri_screen->max_gl_compat_version = 30;
       dri_screen->max_gl_es1_version = 11;
       dri_screen->max_gl_es2_version = screen->devinfo.is_haswell ? 31 : 30;
-- 
2.12.0