Handle LINK_STATUS in DRM backend
LINK_STATUS connector property is set to
BAD when something bad happened to the link. Sometimes this is set when it needs retraining; often it is an indicator that the modeset couldn't actually complete (e.g. a marginal cable preventing higher-frequency modes from locking and training).
We need to:
- check the
LINK_STATUSconnector property whenever we get hotplug notifications
BAD, try setting the current mode again whilst resetting the property to
- if we get another failure, blacklist the current mode and step down one