drm/i915/guc: Move GuC wq_check_space to alloc_request_extras

Split GuC work queue space checking from submission and move it to
ring_alloc_request_extras. The reason is that failure in later
i915_add_request() won't be handled. In the case timeout happens,
driver can return early in order to handle the error.

v1: Move wq_reserve_space to ring_reserve_space
v2: Move wq_reserve_space to alloc_request_extras (Chris Wilson)
v3: The work queue head pointer is cached by driver now. So we can
    quickly return if space is available.
    s/reserve/check/g (Dave Gordon)
v4: Update cached wq head after ring doorbell; check wq space before
    ring doorbell in case unexpected error happens; call wq space
    check only when GuC submission is enabled. (Dave Gordon)

Signed-off-by: Alex Dai <yu.dai@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1450295155-10050-1-git-send-email-yu.dai@intel.com
Reviewed-by: Dave Gordon <david.s.gordon@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 973487a73be1..e09505827394 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -670,6 +670,19 @@ int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request
 			return ret;
 	}
 
+	if (i915.enable_guc_submission) {
+		/*
+		 * Check that the GuC has space for the request before
+		 * going any further, as the i915_add_request() call
+		 * later on mustn't fail ...
+		 */
+		struct intel_guc *guc = &request->i915->guc;
+
+		ret = i915_guc_wq_check_space(guc->execbuf_client);
+		if (ret)
+			return ret;
+	}
+
 	return 0;
 }