drm/i915/ringbuffer: Use the HEAD auto-reporting mechanism
My Sandybridge only reports 0 for the ring buffer registers, causing it
to hang as soon as we exhaust the available ring. As a workaround, take
advantage of our huge ring buffers and use the auto-reporting mechanism
to update the status page with the HEAD location every 64 KiB.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 2e72d3a..390aa21 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -174,7 +174,7 @@
I915_WRITE_CTL(ring,
((ring->gem_object->size - PAGE_SIZE) & RING_NR_PAGES)
- | RING_NO_REPORT | RING_VALID);
+ | RING_REPORT_64K | RING_VALID);
/* If the head is still not zero, the ring is dead */
if ((I915_READ_CTL(ring) & RING_VALID) == 0 ||
@@ -691,6 +691,17 @@
struct drm_device *dev = ring->dev;
drm_i915_private_t *dev_priv = dev->dev_private;
unsigned long end;
+ u32 head;
+
+ head = intel_read_status_page(ring, 4);
+ if (head) {
+ ring->head = head & HEAD_ADDR;
+ ring->space = ring->head - (ring->tail + 8);
+ if (ring->space < 0)
+ ring->space += ring->size;
+ if (ring->space >= n)
+ return 0;
+ }
trace_i915_ring_wait_begin (dev);
end = jiffies + 3 * HZ;