[PATCH 45/45] drm/i915/fbdev: Flush mode configuration before lastclose

[Chris Wilson]

During lastclose, we call intel_fbdev_restore_mode() to switch back to
the fbcon configuration on return to VT. However, if we have not yet
finished the asynchronous fbdev initialisation, the current mode will be
invalid and trigger WARNs upon application.

Serialise with the outstanding initialisation if the first application
exits quickly. Note that to hit this in practice requires using an
unregistered async_domain as otherwise modprobe will force a full
synchronisation prior to init() completing.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_fbdev.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
index 9e74d952fa59..37f235669358 100644
--- a/drivers/gpu/drm/i915/intel_fbdev.c
+++ b/drivers/gpu/drm/i915/intel_fbdev.c
@@ -832,6 +832,11 @@ void intel_fbdev_restore_mode(struct drm_device *dev)
 	if (!ifbdev)
 		return;
 
+	if (ifbdev->cookie) {
+		async_synchronize_cookie(ifbdev->cookie + 1);
+		ifbdev->cookie = 0;
+	}
+
 	fb_helper = &ifbdev->helper;
 
 	ret = drm_fb_helper_restore_fbdev_mode_unlocked(fb_helper);
-- 
2.8.1