drm/i915: Apply strongly ordered RCS breadcrumb to gen8/legacy

For legacy ringbuffer mode, we need the new ordered breadcrumb emission
tried and tested on execlists in order to avoid the dreaded "missed
interrupt" syndrome. A secondary advantage of the execlists method is
that it writes to an arbitrary address, useful if one wants to write a
breadcrumb elsewhere.

This fix is taken from commit 7c17d377 (drm/i915: Use ordered seqno
write interrupt generation on gen8+ execlists).
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461932305-14637-1-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_lrc.c

@@ -1767,11 +1767,6 @@ static void bxt_a_set_seqno(struct intel_engine_cs *engine, u32 seqno)
  */
 #define WA_TAIL_DWORDS 2
 
-static inline u32 hws_seqno_address(struct intel_engine_cs *engine)
-{
-	return engine->status_page.gfx_addr + I915_GEM_HWS_INDEX_ADDR;
-}
-
 static int gen8_emit_request(struct drm_i915_gem_request *request)
 {
 	struct intel_ringbuffer *ringbuf = request->ringbuf;
@@ -1787,7 +1782,7 @@ static int gen8_emit_request(struct drm_i915_gem_request *request)
 	intel_logical_ring_emit(ringbuf,
 				(MI_FLUSH_DW + 1) | MI_FLUSH_DW_OP_STOREDW);
 	intel_logical_ring_emit(ringbuf,
-				hws_seqno_address(request->engine) |
+				intel_hws_seqno_address(request->engine) |
 				MI_FLUSH_DW_USE_GTT);
 	intel_logical_ring_emit(ringbuf, 0);
 	intel_logical_ring_emit(ringbuf, i915_gem_request_get_seqno(request));
@@ -1817,7 +1812,8 @@ static int gen8_emit_request_render(struct drm_i915_gem_request *request)
 				(PIPE_CONTROL_GLOBAL_GTT_IVB |
 				 PIPE_CONTROL_CS_STALL |
 				 PIPE_CONTROL_QW_WRITE));
-	intel_logical_ring_emit(ringbuf, hws_seqno_address(request->engine));
+	intel_logical_ring_emit(ringbuf,
+				intel_hws_seqno_address(request->engine));
 	intel_logical_ring_emit(ringbuf, 0);
 	intel_logical_ring_emit(ringbuf, i915_gem_request_get_seqno(request));
 	/* We're thrashing one dword of HWS. */

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -1430,6 +1430,35 @@ gen6_add_request(struct drm_i915_gem_request *req)
 	return 0;
 }
 
+static int
+gen8_render_add_request(struct drm_i915_gem_request *req)
+{
+	struct intel_engine_cs *engine = req->engine;
+	int ret;
+
+	if (engine->semaphore.signal)
+		ret = engine->semaphore.signal(req, 8);
+	else
+		ret = intel_ring_begin(req, 8);
+	if (ret)
+		return ret;
+
+	intel_ring_emit(engine, GFX_OP_PIPE_CONTROL(6));
+	intel_ring_emit(engine, (PIPE_CONTROL_GLOBAL_GTT_IVB |
+				 PIPE_CONTROL_CS_STALL |
+				 PIPE_CONTROL_QW_WRITE));
+	intel_ring_emit(engine, intel_hws_seqno_address(req->engine));
+	intel_ring_emit(engine, 0);
+	intel_ring_emit(engine, i915_gem_request_get_seqno(req));
+	/* We're thrashing one dword of HWS. */
+	intel_ring_emit(engine, 0);
+	intel_ring_emit(engine, MI_USER_INTERRUPT);
+	intel_ring_emit(engine, MI_NOOP);
+	__intel_ring_advance(engine);
+
+	return 0;
+}
+
 static inline bool i915_gem_has_seqno_wrapped(struct drm_device *dev,
 					      u32 seqno)
 {
@@ -2751,12 +2780,11 @@ int intel_init_render_ring_buffer(struct drm_device *dev)
 		}
 
 		engine->init_context = intel_rcs_ctx_init;
-		engine->add_request = gen6_add_request;
+		engine->add_request = gen8_render_add_request;
 		engine->flush = gen8_render_ring_flush;
 		engine->irq_get = gen8_ring_get_irq;
 		engine->irq_put = gen8_ring_put_irq;
 		engine->irq_enable_mask = GT_RENDER_USER_INTERRUPT;
-		engine->irq_seqno_barrier = gen6_seqno_barrier;
 		engine->get_seqno = ring_get_seqno;
 		engine->set_seqno = ring_set_seqno;
 		if (i915_semaphore_is_enabled(dev)) {

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -489,4 +489,9 @@ static inline u32 intel_ring_get_tail(struct intel_ringbuffer *ringbuf)
  */
 #define MIN_SPACE_FOR_ADD_REQUEST 336
 
+static inline u32 intel_hws_seqno_address(struct intel_engine_cs *engine)
+{
+	return engine->status_page.gfx_addr + I915_GEM_HWS_INDEX_ADDR;
+}
+
 #endif /* _INTEL_RINGBUFFER_H_ */