(In reply to Ioannis Panagiotopoulos from comment #78)
> I replaced the firmware file and run update-initramfs -u
> The system still hangs when it starts X-server on boot.
> My gpu is Club3D R9 390

I don't know if it can help upstream, but Alex asked in comment #1 for vbios
dump, perhaps he will need yours too! (he wrote how to do that)

(In reply to Ioannis Panagiotopoulos from comment #79)
> Ok, after further testing, It ends up that it might be a xserver driver
> problem. I downgraded to ver 7.3.0 x-server driver and the system booted
> with dpm enabled, however the Xserver did not have Hardware acceleration.
> Upgrading to the latest (7.6.x), makes the x-server fail to start with
> enabled dpm.

Well, if your Xserver is not able to get DRI working, you probably do not have
the opportunity to trigger the bug. It's something you must fix first. ^_^

To prevent the auto profile to hang up your GPU while you're playing with your
xserver to fix it while dpm is enabled, do something like that, they looks like
safe options for some people like me:

echo 'low' > '/sys/class/drm/card0/device/power_dpm_force_performance_level'
echo 'battery' > '/sys/class/drm/card0/device/power_dpm_state'

After you get your xserver working with direct rendering enabled, try to do:

echo 'auto' > '/sys/class/drm/card0/device/power_dpm_force_performance_level'

and see if it still crashes.