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.
References: https://bugs.freedesktop.org/show_bug.cgi?id=76554 Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> Cc: Ville Syrjälä <ville.syrj...@linux.intel.com> --- drivers/gpu/drm/i915/intel_ringbuffer.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index 45e3ec927051..0a37ac0d9c0d 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -537,6 +537,15 @@ 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@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
