drm/i915: Disable AsyncFlip performance optimisations

This is a required workarounds for all products, especially on gen6+
where it causes the command streamer to fail to parse instructions
following a WAIT_FOR_EVENT. We use WAIT_FOR_EVENT for synchronising
between the GPU and the display engines, and so this bit being unset may
cause hangs.

References: https://bugzilla.kernel.org/show_bug.cgi?id=52311
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

2 files changed, 14 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index b401788e1791..59afb7eb6db6 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -533,6 +533,7 @@
 #define MI_MODE         0x0209c
 # define VS_TIMER_DISPATCH                              (1 << 6)
 # define MI_FLUSH_ENABLE                                (1 << 12)
+# define ASYNC_FLIP_PERF_DISABLE                        (1 << 14)
 
 #define GEN6_GT_MODE    0x20d0
 #define   GEN6_GT_MODE_HI                               (1 << 9)
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index ae253e04c391..1f46a8bf2b05 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -505,13 +505,20 @@ static int init_render_ring(struct intel_ring_buffer *ring)
         struct drm_i915_private *dev_priv = dev->dev_private;
         int ret = init_ring_common(ring);
 
-        if (INTEL_INFO(dev)->gen > 3) {
+        if (INTEL_INFO(dev)->gen > 3)
                 I915_WRITE(MI_MODE, _MASKED_BIT_ENABLE(VS_TIMER_DISPATCH));
-                if (IS_GEN7(dev))
-                        I915_WRITE(GFX_MODE_GEN7,
-                                   _MASKED_BIT_DISABLE(GFX_TLB_INVALIDATE_ALWAYS) |
-                                   _MASKED_BIT_ENABLE(GFX_REPLAY_MODE));
-        }
+
+        /* We need to disable the AsyncFlip performance optimisations in order
+         * to use MI_WAIT_FOR_EVENT within the CS. It should already be
+         * programmed to '1' on all products.
+         */
+        if (INTEL_INFO(dev)->gen >= 6)
+                I915_WRITE(MI_MODE, _MASKED_BIT_ENABLE(ASYNC_FLIP_PERF_DISABLE));
+
+        if (IS_GEN7(dev))
+                I915_WRITE(GFX_MODE_GEN7,
+                           _MASKED_BIT_DISABLE(GFX_TLB_INVALIDATE_ALWAYS) |
+                           _MASKED_BIT_ENABLE(GFX_REPLAY_MODE));
 
         if (INTEL_INFO(dev)->gen >= 5) {
                 ret = init_pipe_control(ring);