drm/i915/fbc: extract intel_fbc_can_enable()

Extract that part of the code to a new function and call this function
only once during intel_fbc_choose_crtc() instead of once per plane.
Those checks are independent from planes/CRTCs.
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1478883461-20201-4-git-send-email-paulo.r.zanoni@intel.com

drivers/gpu/drm/i915/intel_fbc.c

@@ -854,9 +854,8 @@ static bool intel_fbc_can_activate(struct intel_crtc *crtc)
 	return true;
 }
 
-static bool intel_fbc_can_choose(struct intel_crtc *crtc)
+static bool intel_fbc_can_enable(struct drm_i915_private *dev_priv)
 {
-	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
 	struct intel_fbc *fbc = &dev_priv->fbc;
 
 	if (intel_vgpu_active(dev_priv)) {
@@ -874,6 +873,14 @@ static bool intel_fbc_can_choose(struct intel_crtc *crtc)
 		return false;
 	}
 
+	return true;
+}
+
+static bool intel_fbc_can_choose(struct intel_crtc *crtc)
+{
+	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
+	struct intel_fbc *fbc = &dev_priv->fbc;
+
 	if (fbc_on_pipe_a_only(dev_priv) && crtc->pipe != PIPE_A) {
 		fbc->no_fbc_reason = "no enabled pipes can have FBC";
 		return false;
@@ -1085,6 +1092,9 @@ void intel_fbc_choose_crtc(struct drm_i915_private *dev_priv,
 	if (!fbc_crtc_present && fbc->crtc != NULL)
 		goto out;
 
+	if (!intel_fbc_can_enable(dev_priv))
+		goto out;
+
 	/* Simply choose the first CRTC that is compatible and has a visible
 	 * plane. We could go for fancier schemes such as checking the plane
 	 * size, but this would just affect the few platforms that don't tie FBC