Invalid three-monitor setup configured for LVDS/DP/HDMI

Submitted by Simon Richter

Assigned to Xorg Project Team

Link to original bug (#107650)

Description

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)":
DP-okay.log