Comment # 8 on bug 996543 from Takashi Iwai

(In reply to Bernhard Wiedemann from comment #7)
> > Also, could you try S3 with nomodeset boot option?  This will lead to a
> > broken graphics but the remote access should work after the successful
> > resume.  If nomodeset survives, it implies a radeon driver problem.
> 
> also crashed with nomodeset. No network
> Even with rcxdm stop before suspend.

It's interesting.  So, the issue isn't about radeon but in another place.
Could you test "freezer", "devices", etc, in /sys/power/pm_test, as described
in $LINUX/Documentation/power/basic-pm-debugging.txt?

  echo freezer > /sys/power/pm_test
  echo mem > /sys/power/state

I guess either freezer or devices (maybe latter) would already cause the
problem.