From: Eric Anholt <eric@anholt.net>
Date: Fri, 28 Apr 2017 15:42:22 -0700
Subject: drm/vc4: Don't try to initialize FBDEV if we're only bound to V3D.
Git-commit: 1e70bdcbeb210afedc8f3103ff4fe295c2fa9fc1
Patch-mainline: v4.13-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

There's no sense in having an fbdev if there's no display, since
connectors don't get hotplugged to this hardware.  On Cygnus we were
getting a dmesg error from passing in num_connectors (0), when that
argument is supposed to be the maximum number of cloned connectors per
CRTC (1).

Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170428224223.21904-2-eric@anholt.net

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/vc4/vc4_kms.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/vc4/vc4_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_kms.c
@@ -230,10 +230,12 @@ int vc4_kms_load(struct drm_device *dev)
 
 	drm_mode_config_reset(dev);
 
-	vc4->fbdev = drm_fbdev_cma_init(dev, 32,
-					dev->mode_config.num_connector);
-	if (IS_ERR(vc4->fbdev))
-		vc4->fbdev = NULL;
+	if (dev->mode_config.num_connector) {
+		vc4->fbdev = drm_fbdev_cma_init(dev, 32,
+						dev->mode_config.num_connector);
+		if (IS_ERR(vc4->fbdev))
+			vc4->fbdev = NULL;
+	}
 
 	drm_kms_helper_poll_init(dev);