drm/i915: extract FBC_MULTIPLE_PIPES check

I have two separate refactor ideas that require extracting this to a
separate function. I'm not sure which idea I'll end choosing, but
since both will require extracting this function, let's do this now.

Notice that this is just code moving. Any possible problems with the
current multiple pipes check should be fixed in later commits.
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_fbc.c

@@ -493,24 +493,17 @@ static struct drm_crtc *intel_fbc_find_crtc(struct drm_i915_private *dev_priv)
 {
 	struct drm_crtc *crtc = NULL, *tmp_crtc;
 	enum pipe pipe;
-	bool pipe_a_only = false, one_pipe_only = false;
+	bool pipe_a_only = false;
 
 	if (IS_HASWELL(dev_priv) || INTEL_INFO(dev_priv)->gen >= 8)
 		pipe_a_only = true;
-	else if (INTEL_INFO(dev_priv)->gen <= 4)
-		one_pipe_only = true;
 
 	for_each_pipe(dev_priv, pipe) {
 		tmp_crtc = dev_priv->pipe_to_crtc_mapping[pipe];
 
 		if (intel_crtc_active(tmp_crtc) &&
-		    to_intel_plane_state(tmp_crtc->primary->state)->visible) {
-			if (one_pipe_only && crtc) {
-				set_no_fbc_reason(dev_priv, FBC_MULTIPLE_PIPES);
-				return NULL;
-			}
+		    to_intel_plane_state(tmp_crtc->primary->state)->visible)
 			crtc = tmp_crtc;
-		}
 
 		if (pipe_a_only)
 			break;
@@ -524,6 +517,26 @@ static struct drm_crtc *intel_fbc_find_crtc(struct drm_i915_private *dev_priv)
 	return crtc;
 }
 
+static bool multiple_pipes_ok(struct drm_i915_private *dev_priv)
+{
+	enum pipe pipe;
+	int n_pipes = 0;
+	struct drm_crtc *crtc;
+
+	if (INTEL_INFO(dev_priv)->gen > 4)
+		return true;
+
+	for_each_pipe(dev_priv, pipe) {
+		crtc = dev_priv->pipe_to_crtc_mapping[pipe];
+
+		if (intel_crtc_active(crtc) &&
+		    to_intel_plane_state(crtc->primary->state)->visible)
+			n_pipes++;
+	}
+
+	return (n_pipes < 2);
+}
+
 static int find_compression_threshold(struct drm_i915_private *dev_priv,
 				      struct drm_mm_node *node,
 				      int size,
@@ -710,6 +723,11 @@ static void __intel_fbc_update(struct drm_i915_private *dev_priv)
 	if (!crtc)
 		goto out_disable;
 
+	if (!multiple_pipes_ok(dev_priv)) {
+		set_no_fbc_reason(dev_priv, FBC_MULTIPLE_PIPES);
+		goto out_disable;
+	}
+
 	intel_crtc = to_intel_crtc(crtc);
 	fb = crtc->primary->fb;
 	obj = intel_fb_obj(fb);