drm/i915: Make request's wait-for-space explicit

At the start of building a request, we would wait for roughly enough
space to fit the average request (to reduce the likelihood of having to
wait and abort partway through request construction). To achieve we
would try to begin a 0-length command packet, this just adds extra
confusion so make the wait-for-space explicit, as in the next patch we
want to move it from the backend to the i915_gem_request_alloc() so it
can ensure that the wait-for-space is the first operation in building a
new request.

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/20171115151204.8105-2-chris@chris-wilson.co.uk

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 58d050a..ebd9596 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1180,7 +1180,7 @@ static int execlists_request_alloc(struct drm_i915_gem_request *request)
 {
 	struct intel_engine_cs *engine = request->engine;
 	struct intel_context *ce = &request->ctx->engine[engine->id];
-	u32 *cs;
+	int ret;
 
 	GEM_BUG_ON(!ce->pin_count);
 
@@ -1190,9 +1190,9 @@ static int execlists_request_alloc(struct drm_i915_gem_request *request)
 	 */
 	request->reserved_space += EXECLISTS_REQUEST_SIZE;
 
-	cs = intel_ring_begin(request, 0);
-	if (IS_ERR(cs))
-		return PTR_ERR(cs);
+	ret = intel_ring_wait_for_space(request->ring, request->reserved_space);
+	if (ret)
+		return ret;
 
 	/* Note that after this point, we have committed to using
 	 * this request as it is being used to both track the