drm/i915: Refactor tests for validity of RING_TAIL

Whilst I like having the assertions clearly visible in the code, they
are quite repetitious! As we find new limits we want to incorporate into
the set of assertions, it make sense to refactor them to a common
routine.

v2: Add a guc holdout.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170327131412.20293-1-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

drivers/gpu/drm/i915/i915_guc_submission.c

@@ -481,7 +481,7 @@ static void guc_wq_item_append(struct i915_guc_client *client,
 
 	/* The GuC firmware wants the tail index in QWords, not bytes */
 	tail = rq->tail;
-	GEM_BUG_ON(tail & 7);
+	assert_ring_tail_valid(rq->ring, rq->tail);
 	tail >>= 3;
 	GEM_BUG_ON(tail > WQ_RING_TAIL_MAX);
 

drivers/gpu/drm/i915/intel_lrc.c

@@ -326,8 +326,7 @@ static u64 execlists_update_context(struct drm_i915_gem_request *rq)
 		rq->ctx->ppgtt ?: rq->i915->mm.aliasing_ppgtt;
 	u32 *reg_state = ce->lrc_reg_state;
 
-	GEM_BUG_ON(!IS_ALIGNED(rq->tail, 8));
-	GEM_BUG_ON(rq->tail >= rq->ring->size);
+	assert_ring_tail_valid(rq->ring, rq->tail);
 	reg_state[CTX_RING_TAIL+1] = rq->tail;
 
 	/* True 32b PPGTT with dynamic page allocation: update PDP
@@ -1282,8 +1281,7 @@ static void reset_common_ring(struct intel_engine_cs *engine,
 	request->tail =
 		intel_ring_wrap(request->ring,
 				request->wa_tail - WA_TAIL_DWORDS*sizeof(u32));
-	GEM_BUG_ON(!IS_ALIGNED(request->tail, 8));
-	GEM_BUG_ON(request->tail >= request->ring->size);
+	assert_ring_tail_valid(request->ring, request->tail);
 }
 
 static int intel_logical_ring_emit_pdps(struct drm_i915_gem_request *req)
@@ -1494,8 +1492,7 @@ static void gen8_emit_breadcrumb(struct drm_i915_gem_request *request, u32 *cs)
 	*cs++ = MI_USER_INTERRUPT;
 	*cs++ = MI_NOOP;
 	request->tail = intel_ring_offset(request, cs);
-	GEM_BUG_ON(!IS_ALIGNED(request->tail, 8));
-	GEM_BUG_ON(request->tail >= request->ring->size);
+	assert_ring_tail_valid(request->ring, request->tail);
 
 	gen8_emit_wa_tail(request, cs);
 }
@@ -1523,8 +1520,7 @@ static void gen8_emit_breadcrumb_render(struct drm_i915_gem_request *request,
 	*cs++ = MI_USER_INTERRUPT;
 	*cs++ = MI_NOOP;
 	request->tail = intel_ring_offset(request, cs);
-	GEM_BUG_ON(!IS_ALIGNED(request->tail, 8));
-	GEM_BUG_ON(request->tail >= request->ring->size);
+	assert_ring_tail_valid(request->ring, request->tail);
 
 	gen8_emit_wa_tail(request, cs);
 }

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -774,8 +774,7 @@ static void i9xx_submit_request(struct drm_i915_gem_request *request)
 
 	i915_gem_request_submit(request);
 
-	GEM_BUG_ON(!IS_ALIGNED(request->tail, 8));
-	GEM_BUG_ON(request->tail >= request->ring->size);
+	assert_ring_tail_valid(request->ring, request->tail);
 	I915_WRITE_TAIL(request->engine, request->tail);
 }
 
@@ -787,8 +786,7 @@ static void i9xx_emit_breadcrumb(struct drm_i915_gem_request *req, u32 *cs)
 	*cs++ = MI_USER_INTERRUPT;
 
 	req->tail = intel_ring_offset(req, cs);
-	GEM_BUG_ON(!IS_ALIGNED(req->tail, 8));
-	GEM_BUG_ON(req->tail >= req->ring->size);
+	assert_ring_tail_valid(req->ring, req->tail);
 }
 
 static const int i9xx_emit_breadcrumb_sz = 4;
@@ -827,8 +825,7 @@ static void gen8_render_emit_breadcrumb(struct drm_i915_gem_request *req,
 	*cs++ = MI_NOOP;
 
 	req->tail = intel_ring_offset(req, cs);
-	GEM_BUG_ON(!IS_ALIGNED(req->tail, 8));
-	GEM_BUG_ON(req->tail >= req->ring->size);
+	assert_ring_tail_valid(req->ring, req->tail);
 }
 
 static const int gen8_render_emit_breadcrumb_sz = 8;

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -529,6 +529,17 @@ intel_ring_offset(const struct drm_i915_gem_request *req, void *addr)
 	return intel_ring_wrap(req->ring, offset);
 }
 
+static inline void
+assert_ring_tail_valid(const struct intel_ring *ring, unsigned int tail)
+{
+	/* We could combine these into a single tail operation, but keeping
+	 * them as seperate tests will help identify the cause should one
+	 * ever fire.
+	 */
+	GEM_BUG_ON(!IS_ALIGNED(tail, 8));
+	GEM_BUG_ON(tail >= ring->size);
+}
+
 void intel_ring_update_space(struct intel_ring *ring);
 
 void intel_engine_init_global_seqno(struct intel_engine_cs *engine, u32 seqno);