[Intel-gfx] [PATCH] drm/i915: Use discardable buffers for rings

[Chris Wilson]

The contents of a ring are only valid between HEAD and TAIL, when the
ring is idle (HEAD == TAIL) we can simply let the pages go under memory
pressue if they are not pinned by an active context. And new content
will be written and so the ring will again be valid between HEAD and
TAIL, everything outside can be discarded.

Note that we take care of ensuring that we do not reset the HEAD
backwards following a GPU hang on an idle ring.

The same precautions are what enable us to use stolen memory for rings.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 7d2e5df61028..0cfffc9b4e8f 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1165,7 +1165,7 @@ intel_ring_create_vma(struct drm_i915_private *dev_priv, int size)
 
 	obj = i915_gem_object_create_stolen(dev_priv, size);
 	if (!obj)
-		obj = i915_gem_object_create(dev_priv, size);
+		obj = i915_gem_object_create_internal(dev_priv, size);
 	if (IS_ERR(obj))
 		return ERR_CAST(obj);
 
-- 
2.11.0