We may only start to set up the new register values after having confirmed that the ring is truely off. Otherwise the hw might lose the newly written register values. This is caught later on in the init sequence, when we check whether the register writes have stuck. Cc: stable at vger.kernel.org Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50522 Tested-by: Yang Guang <guang.a.yang at intel.com> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch> --- drivers/gpu/drm/i915/intel_ringbuffer.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index bf0195a..5b19917 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -289,8 +289,6 @@ static int init_ring_common(struct intel_ring_buffer *ring) I915_WRITE_HEAD(ring, 0); ring->write_tail(ring, 0); - /* Initialize the ring. */ - I915_WRITE_START(ring, obj->gtt_offset); head = I915_READ_HEAD(ring) & HEAD_ADDR; /* G45 ring initialization fails to reset head to zero */ @@ -316,6 +314,10 @@ static int init_ring_common(struct intel_ring_buffer *ring) } } + /* Initialize the ring. This must happen _after_ we have confirmed that + * the ring is off (with the above head == 0 check), otherwise the hw + * might lose the new ring register values. */ + I915_WRITE_START(ring, obj->gtt_offset); I915_WRITE_CTL(ring, ((ring->size - PAGE_SIZE) & RING_NR_PAGES) | RING_VALID); -- 1.7.10.4
