radeon has got some new power management infrastructure:
http://www.botchco.com/agd5f/?p=57

Does that change anything wrt this bug?

Btw. here:
# uname -a
Linux hier 3.11.0-rc1 #2 SMP Sun Jul 21 12:29:18 CEST 2013 x86_64 GNU/Linux
(booted with radeon.dpm=1)
# lspci | grep Radeon
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI]
Seymour [Radeon HD 6400M/7400M Series] (rev ff)

# cat rom 
cat: rom: Invalid argument
# echo 1 > rom
# cat rom 
cat: rom: input/output error # translated from german