Ville found an old w/a documented for g4x that suggested that we need to reset the HEAD after writing START. This is a useful fixup for some of the g4x ring initialisation woes, but as usual, not all. v2: Do the rewrite unconditionally anyway References: https://bugs.freedesktop.org/show_bug.cgi?id=76554 Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> --- drivers/gpu/drm/i915/intel_ringbuffer.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index 45e3ec927051..26ec25afc02a 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -537,6 +537,14 @@ static int init_ring_common(struct intel_engine_cs *ring) * also enforces ordering), otherwise the hw might lose the new ring * register values. */ I915_WRITE_START(ring, i915_gem_obj_ggtt_offset(obj)); + + /* WaClearRingBufHeadRegAtInit:ctg,elk */ + if (I915_READ_HEAD(ring)) + DRM_DEBUG("%s initialization failed [head=%08x], fudging\n", + ring->name, I915_READ_HEAD(ring)); + I915_WRITE_HEAD(ring, 0); + (void)I915_READ_HEAD(ring); + I915_WRITE_CTL(ring, ((ringbuf->size - PAGE_SIZE) & RING_NR_PAGES) | RING_VALID); -- 2.1.0.rc1 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
