drm/i915: Automatic i915_switch_context for legacy

During request construction, after pinning the context we know whether
or not we have to emit a context switch. So move this common operation
from every caller into i915_gem_request_alloc() itself.

v2: Always submit the request if we emitted some commands during request
construction, as typically it also involves changes in global state.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171120102002.22254-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -5045,7 +5045,7 @@ static int __intel_engines_record_defaults(struct drm_i915_private *i915)
 			goto out_ctx;
 		}
 
-		err = i915_switch_context(rq);
+		err = 0;
 		if (engine->init_context)
 			err = engine->init_context(rq);
 

drivers/gpu/drm/i915/i915_gem_context.c

@@ -842,8 +842,7 @@ int i915_switch_context(struct drm_i915_gem_request *req)
 	struct intel_engine_cs *engine = req->engine;
 
 	lockdep_assert_held(&req->i915->drm.struct_mutex);
-	if (i915_modparams.enable_execlists)
-		return 0;
+	GEM_BUG_ON(i915_modparams.enable_execlists);
 
 	if (!req->ctx->engine[engine->id].state) {
 		struct i915_gem_context *to = req->ctx;
@@ -899,7 +898,6 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
 
 	for_each_engine(engine, dev_priv, id) {
 		struct drm_i915_gem_request *req;
-		int ret;
 
 		if (engine_has_idle_kernel_context(engine))
 			continue;
@@ -922,10 +920,7 @@ int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv)
 								 GFP_KERNEL);
 		}
 
-		ret = i915_switch_context(req);
 		i915_add_request(req);
-		if (ret)
-			return ret;
 	}
 
 	return 0;

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -1111,10 +1111,6 @@ static int __reloc_gpu_alloc(struct i915_execbuffer *eb,
 	if (err)
 		goto err_request;
 
-	err = i915_switch_context(rq);
-	if (err)
-		goto err_request;
-
 	err = eb->engine->emit_bb_start(rq,
 					batch->node.start, PAGE_SIZE,
 					cache->gen > 5 ? 0 : I915_DISPATCH_SECURE);
@@ -1960,10 +1956,6 @@ static int eb_submit(struct i915_execbuffer *eb)
 	if (err)
 		return err;
 
-	err = i915_switch_context(eb->request);
-	if (err)
-		return err;
-
 	if (eb->args->flags & I915_EXEC_GEN7_SOL_RESET) {
 		err = i915_reset_gen7_sol_offsets(eb->request);
 		if (err)

drivers/gpu/drm/i915/i915_gem_request.c

@@ -624,6 +624,10 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
 	if (ret)
 		goto err_unpin;
 
+	ret = intel_ring_wait_for_space(ring, MIN_SPACE_FOR_ADD_REQUEST);
+	if (ret)
+		goto err_unreserve;
+
 	/* Move the oldest request to the slab-cache (if not in use!) */
 	req = list_first_entry_or_null(&engine->timeline->requests,
 				       typeof(*req), link);

drivers/gpu/drm/i915/i915_perf.c

@@ -1726,10 +1726,9 @@ static int gen8_switch_to_updated_kernel_context(struct drm_i915_private *dev_pr
 							 GFP_KERNEL);
 	}
 
-	ret = i915_switch_context(req);
 	i915_add_request(req);
 
-	return ret;
+	return 0;
 }
 
 /*

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -1592,6 +1592,10 @@ static int ring_request_alloc(struct drm_i915_gem_request *request)
 	if (ret)
 		return ret;
 
+	ret = i915_switch_context(request);
+	if (ret)
+		return ret;
+
 	request->reserved_space -= LEGACY_REQUEST_SIZE;
 	return 0;
 }

drivers/gpu/drm/i915/selftests/huge_pages.c

@@ -989,13 +989,9 @@ static int gpu_write(struct i915_vma *vma,
 	i915_vma_unpin(batch);
 	i915_vma_close(batch);
 
-	err = i915_switch_context(rq);
-	if (err)
-		goto err_request;
-
-	err = rq->engine->emit_bb_start(rq,
-					batch->node.start, batch->node.size,
-					flags);
+	err = engine->emit_bb_start(rq,
+				    batch->node.start, batch->node.size,
+				    flags);
 	if (err)
 		goto err_request;
 

drivers/gpu/drm/i915/selftests/i915_gem_context.c

@@ -158,10 +158,6 @@ static int gpu_fill(struct drm_i915_gem_object *obj,
 		goto err_batch;
 	}
 
-	err = i915_switch_context(rq);
-	if (err)
-		goto err_request;
-
 	flags = 0;
 	if (INTEL_GEN(vm->i915) <= 5)
 		flags |= I915_DISPATCH_SECURE;

drivers/gpu/drm/i915/selftests/i915_gem_request.c

@@ -459,10 +459,6 @@ empty_request(struct intel_engine_cs *engine,
 	if (IS_ERR(request))
 		return request;
 
-	err = i915_switch_context(request);
-	if (err)
-		goto out_request;
-
 	err = engine->emit_bb_start(request,
 				    batch->node.start,
 				    batch->node.size,
@@ -671,9 +667,6 @@ static int live_all_engines(void *arg)
 			goto out_request;
 		}
 
-		err = i915_switch_context(request[id]);
-		GEM_BUG_ON(err);
-
 		err = engine->emit_bb_start(request[id],
 					    batch->node.start,
 					    batch->node.size,
@@ -790,9 +783,6 @@ static int live_sequential_engines(void *arg)
 			}
 		}
 
-		err = i915_switch_context(request[id]);
-		GEM_BUG_ON(err);
-
 		err = engine->emit_bb_start(request[id],
 					    batch->node.start,
 					    batch->node.size,

drivers/gpu/drm/i915/selftests/intel_hangcheck.c

@@ -114,10 +114,6 @@ static int emit_recurse_batch(struct hang *h,
 	if (err)
 		goto unpin_vma;
 
-	err = i915_switch_context(rq);
-	if (err)
-		goto unpin_hws;
-
 	i915_vma_move_to_active(vma, rq, 0);
 	if (!i915_gem_object_has_active_reference(vma->obj)) {
 		i915_gem_object_get(vma->obj);
@@ -169,7 +165,6 @@ static int emit_recurse_batch(struct hang *h,
 
 	err = rq->engine->emit_bb_start(rq, vma->node.start, PAGE_SIZE, flags);
 
-unpin_hws:
 	i915_vma_unpin(hws);
 unpin_vma:
 	i915_vma_unpin(vma);