https://bugs.freedesktop.org/show_bug.cgi?id=91871
Bug ID: 91871 Summary: link retraining for DP not possible with current design of Atomic modeset framework Product: DRI Version: XOrg git Hardware: All OS: All Status: NEW Severity: normal Priority: medium Component: General Assignee: dri-devel@lists.freedesktop.org Reporter: sivakumar.thulasimani@intel.com
DP spec requires Link training from highest link rate supported by panel to lowest link rate supported by panel.
It is not possible to implement this in the current atomic modeset logic since it splits modeset into two half atomic_check and atomic_commit, where it is expected all values to be calculated in atomic_check and programmed in atomic_commit.
link training being a negotiation phase of DP modeset it is not possible to predict if a training at certain link rate will succeed or not. if it does fail it will require us to disable, calculate new values and enable pll. this is not possible in current DRM Atomic modeset framework.