https://bugzilla.kernel.org/show_bug.cgi?id=90741
--- Comment #60 from Maarten Lankhorst bugs@mblankhorst.nl --- can you add a if (fence->ring == R600_RING_TYPE_DMA_INDEX) udelay(50); to radeon_fence_enable_signaling? after the irq_get again. If that works try udelay(5), if it doesn't udelay(500) ?