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authorChris Wilson <chris@chris-wilson.co.uk>2010-12-09 12:56:37 +0000
committerChris Wilson <chris@chris-wilson.co.uk>2010-12-09 12:53:19 +0000
commit8c0a6bfef165ccdbf5d73afb9dd660107b0c98d5 (patch)
tree09455156e4e46ac5137ddab9ec3aed65bc6a8c59 /drivers/gpu
parent8316f33766a82907c694267ff911e45e256f09f9 (diff)
drm/i915/ringbuffer: Handle wrapping of the autoreported HEAD
If the tail advances beyond the autoreport HEAD value, then we need to fallback to an uncached read of the HEAD register in order to ascertain the correct amount of remaining space in the ringbuffer. Reported-by: Fang, Xun <xunx.fang@intel.com> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=32259 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Diffstat (limited to 'drivers/gpu')
-rw-r--r--drivers/gpu/drm/i915/intel_ringbuffer.c19
-rw-r--r--drivers/gpu/drm/i915/intel_ringbuffer.h5
2 files changed, 11 insertions, 13 deletions
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 89a65be8a3f..31cd7e33e82 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -696,20 +696,17 @@ int intel_wait_ring_buffer(struct drm_device *dev,
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;
do {
- ring->head = I915_READ_HEAD(ring) & HEAD_ADDR;
+ /* If the reported head position has wrapped or hasn't advanced,
+ * fallback to the slow and accurate path.
+ */
+ head = intel_read_status_page(ring, 4);
+ if (head < ring->actual_head)
+ head = I915_READ_HEAD(ring);
+ ring->actual_head = head;
+ ring->head = head & HEAD_ADDR;
ring->space = ring->head - (ring->tail + 8);
if (ring->space < 0)
ring->space += ring->size;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 3126c268198..d2cd0f1efee 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -30,8 +30,9 @@ struct intel_ring_buffer {
struct drm_device *dev;
struct drm_gem_object *gem_object;
- unsigned int head;
- unsigned int tail;
+ u32 actual_head;
+ u32 head;
+ u32 tail;
int space;
struct intel_hw_status_page status_page;