Invalid three-monitor setup configured for LVDS/DP/HDMI
Submitted by Simon Richter
Assigned to Xorg Project Team
Created attachment 141223 X log, three-monitor setup, DP port in HDMI mode (works)
When two external monitors supporting the same timings are connected, the driver attempts to reuse a CRTC, however this fails if one is connected via DP and the other via HDMI or DVI, as the DP link requires a different PLL setup.
xrandr handles this restriction, reporting an error from the CRTC setup (the virtual CRTC 2 just reports failure), but on startup, this check is not performed properly, and the X server starts up with two usable displays and one confused monitor that will neither go to powersave nor show a picture.
Attachment 141223, "X log, three-monitor setup, DP port in HDMI mode (works)":