From 8fd3b90300bec541806dac271de2fd44e2e4e2d2 Mon Sep 17 00:00:00 2001
From: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Date: Thu, 15 Nov 2018 17:32:48 +0100
Subject: drm/fb-helper: Blacklist writeback when adding connectors to fbdev
Git-commit: 8fd3b90300bec541806dac271de2fd44e2e4e2d2
Patch-mainline: v4.20-rc4
References: bsc#1113956

Writeback connectors do not produce any on-screen output and require
special care for use. Such connectors are hidden from enumeration in
DRM resources by default, but they are still picked-up by fbdev.
This makes rather little sense since fbdev is not really adapted for
dealing with writeback.

Moreover, this is also a source of issues when userspace disables the
CRTC (and associated plane) without detaching the CRTC from the
connector (which is hidden by default). In this case, the connector is
still using the CRTC, leading to am "enabled/connectors mismatch" and
eventually the failure of the associated atomic commit. This situation
happens with VC4 testing under IGT GPU Tools.

Filter out writeback connectors in the fbdev helper to solve this.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Maxime Ripard <maxime.ripard@bootlin.com>
Tested-by: Maxime Ripard <maxime.ripard@bootlin.com>
Fixes: 935774cd71fe ("drm: Add writeback connector type")
Cc: <stable@vger.kernel.org> # v4.19+
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181115163248.21168-1-paul.kocialkowski@bootlin.com
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/drm_fb_helper.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index a502f3e519fd..dd852a25d375 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -219,6 +219,9 @@ int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
 	mutex_lock(&fb_helper->lock);
 	drm_connector_list_iter_begin(dev, &conn_iter);
 	drm_for_each_connector_iter(connector, &conn_iter) {
+		if (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK)
+			continue;
+
 		ret = __drm_fb_helper_add_one_connector(fb_helper, connector);
 		if (ret)
 			goto fail;
-- 
2.20.1