drivers - Dual monitor not working - Intel Graphics & Nvidia 960m

I don't really know where to start looking to solve this problem. Searching the web didn't get me very far. I'm not using any special adapter, it's a straight HDMI cable. It's a fresh install of Ubuntu 14.04.3 (later also 15.10). The same monitor, cable and laptop work in Windows.

Curiously

if I unplug the monitor, then I run

sudo apt-get install --reinstall ubuntu-desktop
sudo reboot now

the first time I login, and the first time i plug the cable in, the second screen works without problems (dmesg still complains about WARN_ON(!wm_changed), but no more i2c i2c-1: sendbytes: NAK bailout.). But as soon as the laptop turns off the screens (standby) or I reboot the machine or I unplug the cable, the second screen doesn't work anymore.

Also, if I reinstall ubuntu-desktop, but power off the laptop with the HDMI cable plugged in, this trick doesn't seem to work.

HW:

• acer Aspire V 17 Nitro - Black Edition (Aspire VN7-792G)


• GeForce GTX 960m / Intel Graphics


• the second monitor is connected through the HDMI port

I'm using the proprietary nvidia driver found in the "Additional Drivers" app. But setting that to use the nouveau display driver doesn't help either.

xrandr

roman@roman-aspire:~$ xrandr --query
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 16384 x 16384
eDP1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 382mm x 215mm
   1920x1080      60.0*+   59.9
   1680x1050      60.0     59.9
   1600x1024      60.2
   1400x1050      60.0
   1280x1024      60.0
   1440x900       59.9
   1280x960       60.0
   1360x768       59.8     60.0
   1152x864       60.0
   1024x768       60.0
   800x600        60.3     56.2
   640x480        59.9
DP1 disconnected (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

nvidia-settings sees only one screen.

lshw -c display

roman@roman-aspire:/$ sudo lshw -c display
  *-display
       description: 3D controller
       product: NVIDIA Corporation
       vendor: NVIDIA Corporation
       physical id: 0
       bus info: pci@0000:01:00.0
       version: a2
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list
       configuration: driver=nvidia latency=0
       resources: irq:128 memory:83000000-83ffffff memory:40000000-4fffffff memory:50000000-51ffffff ioport:4000(size=128)
  *-display
       description: VGA compatible controller
       product: Intel Corporation
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 06
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915_bpo latency=0
       resources: irq:126 memory:82000000-82ffffff memory:90000000-9fffffff ioport:5000(size=64)

Could someone please point me in a direction?

UPDATE:
I've installed 15.10. Installed the "Intel Graphics for Linux" drivers. And it still doesn't work. But now when I click on "Detect Displays" in nvidia-settings, the application segfaults. Don't know if this has any relevance.

dmesg when I plug in the monitor

[46290.977521] WARNING: CPU: 0 PID: 958 at /build/linux-NgsOGa/linux-4.2.0/drivers/gpu/drm/i915/intel_pm.c:3404 skl_update_other_pipe_wm+0x1de/0x1f0 [i915]()
[46290.977522] WARN_ON(!wm_changed)
[46290.977522] Modules linked in:
[46290.977524]  visor usbserial uas usb_storage snd_seq_dummy xt_nat xt_tcpudp veth arc4 rfcomm bbswitch(OE) xt_conntrack ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 xt_addrtype iptable_filter ip_tables x_tables nf_nat nf_conntrack br_netfilter bridge stp llc aufs rtsx_usb_ms rtsx_usb_sdmmc memstick rtsx_usb bnep snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic nls_iso8859_1 hid_multitouch joydev i2c_designware_platform i2c_designware_core acer_wmi sparse_keymap intel_rapl snd_hda_intel x86_pkg_temp_thermal intel_powerclamp coretemp snd_hda_codec snd_hda_core kvm_intel nvidia(POE) snd_hwdep kvm crct10dif_pclmul crc32_pclmul snd_pcm aesni_intel uvcvideo aes_x86_64 videobuf2_vmalloc lrw videobuf2_memops ath10k_pci gf128mul snd_seq_midi videobuf2_core
[46290.977546]  glue_helper snd_seq_midi_event ath10k_core v4l2_common ablk_helper cryptd snd_rawmidi videodev ath media snd_seq mac80211 snd_seq_device snd_timer input_leds idma64 virt_dma serio_raw mei_me snd btusb mei cfg80211 soundcore btrtl btbcm btintel bluetooth intel_lpss_pci shpchp acpi_als kfifo_buf industrialio wmi intel_lpss_acpi intel_lpss tpm_crb acpi_pad mac_hid parport_pc ppdev lp parport autofs4 hid_generic usbhid i915 i2c_algo_bit drm_kms_helper drm r8169 ahci mii libahci i2c_hid hid video pinctrl_sunrisepoint pinctrl_intel
[46290.977565] CPU: 0 PID: 958 Comm: Xorg Tainted: P           OE   4.2.0-27-generic #32-Ubuntu
[46290.977566] Hardware name: Acer Aspire VN7-792G/Aspire VN7-792G, BIOS V1.02 09/25/2015
[46290.977567]  0000000000000000 000000007e6118ab ffff880897287628 ffffffff817eae99
[46290.977568]  0000000000000000 ffff880897287680 ffff880897287668 ffffffff8107b9c6
[46290.977569]  ffff880897287730 ffff8808972877d4 ffff88089e3c7000 ffff88089e3c6000
[46290.977571] Call Trace:
[46290.977574]  [] dump_stack+0x45/0x57
[46290.977577]  [] warn_slowpath_common+0x86/0xc0
[46290.977578]  [] warn_slowpath_fmt+0x55/0x70
[46290.977584]  [] skl_update_other_pipe_wm+0x1de/0x1f0 [i915]
[46290.977592]  [] ? zone_statistics+0x7c/0xa0
[46290.977597]  [] skl_update_wm+0x1bb/0x740 [i915]
[46290.977603]  [] intel_update_watermarks+0x1e/0x30 [i915]
[46290.977614]  [] haswell_crtc_enable+0x488/0xa90 [i915]
[46290.977624]  [] __intel_set_mode+0x916/0xb60 [i915]
[46290.977633]  [] intel_crtc_set_config+0x2b6/0x580 [i915]
[46290.977642]  [] ? drm_mode_create+0x25/0x60 [drm]
[46290.977648]  [] drm_mode_set_config_internal+0x66/0x100 [drm]
[46290.977655]  [] drm_mode_setcrtc+0x3e9/0x500 [drm]
[46290.977659]  [] drm_ioctl+0x125/0x610 [drm]
[46290.977665]  [] ? drm_mode_setplane+0x1b0/0x1b0 [drm]
[46290.977667]  [] do_vfs_ioctl+0x295/0x480
[46290.977669]  [] ? __set_task_blocked+0x41/0xa0
[46290.977671]  [] SyS_ioctl+0x79/0x90
[46290.977672]  [] ? SyS_rt_sigprocmask+0x74/0xc0
[46290.977673]  [] entry_SYSCALL_64_fastpath+0x16/0x75
[46290.977674] ---[ end trace 83ee13270bae676a ]---
[46294.680523] [drm] GMBUS [i915 gmbus dpb] timed out, falling back to bit banging on pin 5

and then an endless:

[46295.906998] i2c i2c-1: sendbytes: NAK bailout.