Comment # 10 on bug 42960 from Alex Deucher

(In reply to comment #9)
> I booted Linux 3.13.6 with the drm.debug=4 parameter - it looks like the
> internal LVDS output is set to use a different CRTC than the HDMI output,
> even in clone mode.

Neither the driver nor the vbios uses the same crtc for clones since the
displays almost always require different timings even if they are the same
resolution.