drm/i915: Use plane->get_hw_state() for initial plane fb readout

Since we now have a ->get_hw_state() method for planes, let's use
that during the initial plane fb readout.

v2: s/plane/i9xx_plane/ etc. (James)

Cc: James Ausmus <james.ausmus@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Suggested-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: NJames Ausmus <james.ausmus@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171117191917.11506-10-ville.syrjala@linux.intel.comSigned-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -7413,8 +7413,7 @@ i9xx_get_initial_plane_config(struct intel_crtc *crtc,
 	struct drm_framebuffer *fb;
 	struct intel_framebuffer *intel_fb;
 
-	val = I915_READ(DSPCNTR(i9xx_plane));
-	if (!(val & DISPLAY_PLANE_ENABLE))
+	if (!plane->get_hw_state(plane))
 		return;
 
 	intel_fb = kzalloc(sizeof(*intel_fb), GFP_KERNEL);
@@ -7427,6 +7426,8 @@ i9xx_get_initial_plane_config(struct intel_crtc *crtc,
 
 	fb->dev = dev;
 
+	val = I915_READ(DSPCNTR(i9xx_plane));
+
 	if (INTEL_GEN(dev_priv) >= 4) {
 		if (val & DISPPLANE_TILED) {
 			plane_config->tiling = I915_TILING_X;
@@ -8442,6 +8443,9 @@ skylake_get_initial_plane_config(struct intel_crtc *crtc,
 	struct drm_framebuffer *fb;
 	struct intel_framebuffer *intel_fb;
 
+	if (!plane->get_hw_state(plane))
+		return;
+
 	intel_fb = kzalloc(sizeof(*intel_fb), GFP_KERNEL);
 	if (!intel_fb) {
 		DRM_DEBUG_KMS("failed to alloc fb\n");
@@ -8453,8 +8457,6 @@ skylake_get_initial_plane_config(struct intel_crtc *crtc,
 	fb->dev = dev;
 
 	val = I915_READ(PLANE_CTL(pipe, plane_id));
-	if (!(val & PLANE_CTL_ENABLE))
-		goto error;
 
 	pixel_format = val & PLANE_CTL_FORMAT_MASK;