multihead output bug where? kernel? driver? server?

[Felix Miata]

Whether starting X including this:
xrandr --dpi 144 --output DVI-0 --mode 1920x1080 --above VGA-0 --output VGA-0
--primary --mode 1920x1440 # ati dual

works or not depends on which Radeon gfxcard used, and how new the software.

The cards' info:
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/hwinfo-gfx-rv380fan.txt X600
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/hwinfo-gfx-rv516.txt X1300
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/hwinfo-gfx-cedarPC-big41.txt

rv380 works as expected regardless at least as far back as openSUSE 13.1 k3.12.
openSUSE Tumbleweed 3.19.0:
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/xorg.0.log-under1440xover1080-rv380fan-OK

cedar works as expected as recently as Mageia 4 k3.12 and openSUSE 13.1 k3.12:
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/xorg.0.log-under1440over1080-os131-cedarOK
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/xorg.0.log-under1440-over1080-mag4-cedarOK

Failures in the form of black screen on only one output using rv516 and cedar
in the following:
Fedora 20 k3.17.7 cedar (black VGA):
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/xorg.0.log-under1440bad-over1080OK-f20-cedar
openSUSE 13.2 k3.16.7 cedar (black VGA):
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/xorg.0.log-under1440bad-over1080OK-os132-cedar
Fedora 21 cedar (black VGA):
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/xorg.0.log-under1440bad-over1080OK-cedarF21-k3177
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/xorg.0.log-under1440bad-over1080OK-cedarF21-k3187
openSUSE Tumbleweed k3.19.0 rv516 (black DVI):
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/xorg.0.log-under1440OKxover1080bad-rv516
openSUSE Tumbleweed k3.19.0 cedar (black VGA):
http://fm.no-ip.com/Tmp/Linux/Xorg/ATIdual/xorg.0.log-under1440bad-over1080OK-cedar

All of above pertains to same system, with only changes made being:

1-which OS booted
2-which ATI gfxcard installed

With necessary xrandr output descriptors for Intel, results are as expected
using onboard Intel gfx instead of ATI PCIe cards.

On cedar in Tumbleweed at least, dropping analog output mode from 1920x1440
to 1600x1200 produces expected output.

Is this a known ATI driver bug? Somebody else's bug? WAD? Hardware flaws?
User error?
-- 
"The wise are known for their understanding, and pleasant
words are persuasive." Proverbs 16:21 (New Living Translation)

 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata  ***  http://fm.no-ip.com/