drm/i915: Reserve ring buffer space for i915_add_request() commands

[deliverable/linux.git] / drivers / gpu / drm / i915 / intel_ringbuffer.h

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 64850293559c4fbe110104d910f6c01f816f7feb..73db3ae8f237a0e9cae46b5a129d629efb22abd9 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -106,6 +106,9 @@ struct intel_ringbuffer {
        int space;
        int size;
        int effective_size;
+       int reserved_size;
+       int reserved_tail;
+       bool reserved_in_use;
 
        /** We track the position of the requests in the ring buffer, and
         * when each is retired we increment last_retired_head as the GPU
@@ -472,4 +475,26 @@ intel_ring_get_request(struct intel_engine_cs *ring)
        return ring->outstanding_lazy_request;
 }
 
+/*
+ * Arbitrary size for largest possible 'add request' sequence. The code paths
+ * are complex and variable. Empirical measurement shows that the worst case
+ * is ILK at 136 words. Reserving too much is better than reserving too little
+ * as that allows for corner cases that might have been missed. So the figure
+ * has been rounded up to 160 words.
+ */
+#define MIN_SPACE_FOR_ADD_REQUEST      160
+
+/*
+ * Reserve space in the ring to guarantee that the i915_add_request() call
+ * will always have sufficient room to do its stuff. The request creation
+ * code calls this automatically.
+ */
+void intel_ring_reserved_space_reserve(struct intel_ringbuffer *ringbuf, int size);
+/* Cancel the reservation, e.g. because the request is being discarded. */
+void intel_ring_reserved_space_cancel(struct intel_ringbuffer *ringbuf);
+/* Use the reserved space - for use by i915_add_request() only. */
+void intel_ring_reserved_space_use(struct intel_ringbuffer *ringbuf);
+/* Finish with the reserved space - for use by i915_add_request() only. */
+void intel_ring_reserved_space_end(struct intel_ringbuffer *ringbuf);
+
 #endif /* _INTEL_RINGBUFFER_H_ */