drm/i915/ringbuffer: Exclude last 2 cachlines of ring on 845g

BugLink: http://bugs.launchpad.net/bugs/987337

commit 27c1cbd06a7620b354cbb363834f3bb8df4f410d upstream.

The 845g shares the errata with i830 whereby executing a command
within 2 cachelines of the end of the ringbuffer may cause a GPU hang.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 30a9af9..8673581 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1052,7 +1052,7 @@ int intel_init_ring_buffer(struct drm_device *dev,
         * of the buffer.
         */
        ring->effective_size = ring->size;
         * of the buffer.
         */
        ring->effective_size = ring->size;

-       if (IS_I830(ring->dev))
+       if (IS_I830(ring->dev) || IS_845G(ring->dev))

                ring->effective_size -= 128;
 
        return 0;
                ring->effective_size -= 128;
 
        return 0;