commit: f05bb0c7b624252a5e768287e340e8e45df96e42
From: Chris Wilson <ch...@chris-wilson.co.uk>
Date: Sun, 20 Jan 2013 16:33:32 +0000
Subject: drm/i915: GFX_MODE Flush TLB Invalidate Mode must be '1' for
 scanline waits

On SNB, if bit 13 of GFX_MODE, Flush TLB Invalidate Mode, is not set to 1,
the hardware can not program the scanline values. Those scanline values
then control when the signal is sent from the display engine to the render
ring for MI_WAIT_FOR_EVENTs. Note setting this bit means that TLB
invalidations must be performed explicitly through the appropriate bits
being set in PIPE_CONTROL.

References: https://bugzilla.kernel.org/show_bug.cgi?id=52311
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
Reviewed-by: Ben Widawsky <b...@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vet...@ffwll.ch>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c 
b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 1f46a8b..42ff97d 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -515,6 +515,11 @@ static int init_render_ring(struct intel_ring_buffer *ring)
        if (INTEL_INFO(dev)->gen >= 6)
                I915_WRITE(MI_MODE, 
_MASKED_BIT_ENABLE(ASYNC_FLIP_PERF_DISABLE));
 
+       /* Required for the hardware to program scanline values for waiting */
+       if (INTEL_INFO(dev)->gen == 6)
+               I915_WRITE(GFX_MODE,
+                          _MASKED_BIT_ENABLE(GFX_TLB_INVALIDATE_ALWAYS));
+
        if (IS_GEN7(dev))
                I915_WRITE(GFX_MODE_GEN7,
                           _MASKED_BIT_DISABLE(GFX_TLB_INVALIDATE_ALWAYS) |
-- 
1.7.10.4
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