Skylake: second external port does not work

[AMDmi3]

Dell Latitude E7470, drm-next branch, latest ports.

% sysctl hw.model
hw.model: Intel(R) Core(TM) i7-6600U CPU @ 2.60GHz
% uname -a
FreeBSD marakasov 12.0-CURRENT FreeBSD 12.0-CURRENT #0 d71bcb11d(drm-next): Wed Jun 21 17:14:15 MSK 2017     root@marakasov:/usr/obj/usr/src/sys/GENERIC  amd64

The system works fine, but second external connector does not work. xrandr reports:

Screen 0: minimum 320 x 200, current 3520 x 1200, maximum 8192 x 8192
eDP1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
   1920x1080     60.02*+  47.99  
   1400x1050     59.98  
   1280x1024     60.02  
   1280x960      60.00  
   1024x768      60.00  
   800x600       60.32    56.25  
   640x480       59.94  
HDMI1 disconnected (normal left inverted right x axis y axis)
DP1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
DP1-1 connected primary 1600x1200+1920+0 (normal left inverted right x axis y axis) 367mm x 275mm
   1600x1200     60.00*+
   1280x1024     75.02    60.02  
   1152x864      75.00  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   640x480       75.00    59.94  
   720x400       70.08  

There should probably be something like DP1-2.

dmesg:

[drm] Initialized
drmn0: <drmn> on vgapci0
vgapci0: child drmn0 requested pci_enable_io
vgapci0: child drmn0 requested pci_enable_io
[drm] Memory usable by graphics device = 4096M
Failed to add WC MTRR for [0xd0000000-0xdfffffff]: -22; performance may suffer
[drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[drm] Driver supports precise vblank timestamp query.
i915/skl_dmc_ver1_26.bin: could not load firmware image, error 2
[drm] Connector eDP-1: get mode from tunables:
[drm]   - kern.vt.fb.modes.eDP-1
[drm]   - kern.vt.fb.default_mode
[drm] Connector HDMI-A-1: get mode from tunables:
[drm]   - kern.vt.fb.modes.HDMI-A-1
[drm]   - kern.vt.fb.default_mode
[drm] Connector DP-1: get mode from tunables:
[drm]   - kern.vt.fb.modes.DP-1
[drm]   - kern.vt.fb.default_mode
[drm] Connector HDMI-A-2: get mode from tunables:
[drm]   - kern.vt.fb.modes.HDMI-A-2
[drm]   - kern.vt.fb.default_mode
[drm] GuC firmware load skipped
[drm:i915_setup_sysfs] RC6 residency sysfs setup failed
[drm] Initialized i915 1.6.0 20160919 for drmn on minor 0
[drm] Connector DP-2: get mode from tunables:
[drm]   - kern.vt.fb.modes.DP-2
[drm]   - kern.vt.fb.default_mode
VT: Replacing driver "vga" with new "fb".
start FB_INFO:
type=11 height=1080 width=1920 depth=32
cmsize=16 size=8294400
pbase=0xd00c0000 vbase=0xfffff800d00c0000
name=drmn0 flags=0x0 stride=7680 bpp=32
cmap[0]=0 cmap[1]=7f0000 cmap[2]=7f00 cmap[3]=c4a000
end FB_INFO
drmn0: fb0: inteldrmfb frame buffer device
i915/skl_dmc_ver1_26.bin: could not load firmware image, error 2
[drm] Finished loading i915/skl_dmc_ver1_26.bin (v1.26)
[drm] RC6 on
[drm] Connector DP-3: get mode from tunables:
[drm]   - kern.vt.fb.modes.DP-3
[drm]   - kern.vt.fb.default_mode
hdacc1: Unexpected unsolicited response with tag 63: ffffffff
hdacc1: Unexpected unsolicited response with tag 63: ffffffff
[drm] Connector DP-4: get mode from tunables:
[drm]   - kern.vt.fb.modes.DP-4
[drm]   - kern.vt.fb.default_mode
hdacc1: Unexpected unsolicited response with tag 63: ffffffff

[AMDmi3]

My bad. I've solved this by removing xorg.conf (which was created when no external monitors were connected).

[AMDmi3]

PS. Maybe this should be added to troubleshooting along with the suggestion to add user to video group?