drm/vc4: Use the fbdev_cma helpers

Keep the fbdev_cma pointer around so we can use it on hotplog and close
to ensure the frame buffer console is in a useful state.

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c
index c241c8f..ee3e004 100644
--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -21,7 +21,16 @@
 #include "drm_fb_cma_helper.h"
 #include "vc4_drv.h"
 
+static void vc4_output_poll_changed(struct drm_device *dev)
+{
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
+
+	if (vc4->fbdev)
+		drm_fbdev_cma_hotplug_event(vc4->fbdev);
+}
+
 static const struct drm_mode_config_funcs vc4_mode_funcs = {
+	.output_poll_changed = vc4_output_poll_changed,
 	.atomic_check = drm_atomic_helper_check,
 	.atomic_commit = drm_atomic_helper_commit,
 	.fb_create = drm_fb_cma_create,
@@ -29,6 +38,7 @@
 
 int vc4_kms_load(struct drm_device *dev)
 {
+	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	int ret;
 
 	ret = drm_vblank_init(dev, dev->mode_config.num_crtc);
@@ -44,9 +54,11 @@
 
 	drm_mode_config_reset(dev);
 
-	drm_fbdev_cma_init(dev, 32,
-			   dev->mode_config.num_crtc,
-			   dev->mode_config.num_connector);
+	vc4->fbdev = drm_fbdev_cma_init(dev, 32,
+					dev->mode_config.num_crtc,
+					dev->mode_config.num_connector);
+	if (IS_ERR(vc4->fbdev))
+		vc4->fbdev = NULL;
 
 	drm_kms_helper_poll_init(dev);