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.

Cherry-picked from 6aa56062eaba67adfb247cded244fd877329588d.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=31404
Tested-by: Zhao Jian <jian.j.zhao@intel.com>
Cc: stable@kernel.org
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 12 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 7c1f3ff2f788..b83306f9244b 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -177,7 +177,7 @@ static int init_ring_common(struct drm_device *dev,
 
         I915_WRITE_CTL(ring,
                         ((ring->gem_object->size - PAGE_SIZE) & RING_NR_PAGES)
-                        | RING_NO_REPORT | RING_VALID);
+                        | RING_REPORT_64K | RING_VALID);
 
         head = I915_READ_HEAD(ring) & HEAD_ADDR;
         /* If the head is still not zero, the ring is dead */
@@ -692,6 +692,17 @@ int intel_wait_ring_buffer(struct drm_device *dev,
 {
         unsigned long end;
         drm_i915_private_t *dev_priv = dev->dev_private;
+        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;