dix/dispatch.c:4049: AttachOffloadGPU: Assertion `new->current_master == pScreen' failed.

[Paul Menzel]

Dear Linux folks,


Getting Dell Precision 3620 systems with an Intel Skylake system 
i7-6700K, and an external AMD graphics card, the X.Org server does not 
start and hits an assert. The software stack is Linux 4.9.38 and 4.12.5, 
X.Org server 1.19.3 and xf86-video-amdgpu 1.3.0.

```
$ lspci -nn -s 00:01.0
00:01.0 PCI bridge [0604]: Intel Corporation Skylake PCIe Controller 
(x16) [8086:1901] (rev 07)
$ lspci -nn -s 1:00.0
01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. 
[AMD/ATI] Bonaire [FirePro W5100] [1002:6649]
```

The monitor’s DVI cable and a DVI-to-DP adapter is plugged into the 
DisplayPort port of the AMD graphics card. The TTY login screen can be 
shortly seen before GDM tries to start.

Please find the last X.Org server messages below.

```
[…]
(II) Loading /usr/lib/xorg/modules/libfb.so
(II) Module fb: vendor="X.Org Foundation"
         compiled for 1.19.3, module version = 1.0.0
(--) Depth 24 pixmap format is 32 bpp
(==) modeset(G0): Backing store enabled
(==) modeset(G0): Silken mouse enabled
(II) modeset(G0): RandR 1.2 enabled, ignore the following RandR disabled 
message.
(==) modeset(G0): DPMS enabled
(II) modeset(G0): [DRI2] Setup complete
(II) modeset(G0): [DRI2]   DRI driver: i965
(II) modeset(G0): [DRI2]   VDPAU driver: i965
(II) AMDGPU(0): [DRI2] Setup complete
(II) AMDGPU(0): [DRI2]   DRI driver: radeonsi
(II) AMDGPU(0): [DRI2]   VDPAU driver: radeonsi
(II) AMDGPU(0): Front buffer pitch: 6912 bytes
(II) AMDGPU(0): SYNC extension fences enabled
(II) AMDGPU(0): Present extension enabled
(==) AMDGPU(0): DRI3 enabled
(==) AMDGPU(0): Backing store enabled
(II) AMDGPU(0): Direct rendering enabled
(II) AMDGPU(0): Use GLAMOR acceleration.
(II) AMDGPU(0): Acceleration enabled
(==) AMDGPU(0): DPMS enabled
(==) AMDGPU(0): Silken mouse enabled
(II) AMDGPU(0): Set up textured video (glamor)
(II) AMDGPU(0): RandR 1.2 enabled, ignore the following RandR disabled 
message.
(--) RandR disabled
Xorg: 
/dev/shm/bee-root/xorg-server/xorg-server-1.19.3-0/source/dix/dispatch.c:4049: 
AttachOffloadGPU: Assertion `new->current_master == pScreen' failed.
```

The USB keyboard does not work, and the system has to be controlled 
remotely over SSH. Plugging in the DisplayPort cable into the internal 
Intel graphics ports the Linux messages can be seen, but nothing else 
works. Stopping GDM does not bring back the TTY screen. The keyboard 
still does work. Plugging the USB cable out and back in doesn’t fix it 
either.

Trying to disable the internal Intel graphics card, did not fix the 
problem either.


Kind regards,

Paul