Sometimes when my laptop has been suspended, connecting the external screens causes the screens to power on/off in some kind of infinite loop.

I think this is related to the kernel since I get a stack trace in there.

If I let X resume with the laptop screen only, then connected the first external (display port) and after a while the third (hdmi), I can get X on all screens again (without rebooting.)

[273529.408977] ------------[ cut here ]------------
[273529.409026] WARNING: CPU: 0 PID: 1865 at /build/buildd/linux-3.19.0/drivers/gpu/drm/i915/intel_display.c:1256 assert_plane.constprop.87+0x7b/0x90 [i915]()
[273529.409030] plane A assertion failure (expected on, current off)
[273529.409032] Modules linked in: iwlmvm iwlwifi nfc_digital crc_ccitt crc_itu_t uas usb_storage ftdi_sio cp210x pl2303 usbserial asix usbnet mii rfcomm ctr ccm binfmt_misc bnep nfc nls_iso8859_1 arc4 snd_hda_codec_hdmi asus_nb_wmi asus_wmi hid_generic hid_multitouch sparse_keymap intel_rapl iosf_mbi x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm snd_soc_rt5640 snd_soc_rl6231 crct10dif_pclmul dm_multipath snd_soc_core crc32_pclmul ghash_clmulni_intel scsi_dh aesni_intel snd_compress snd_pcm_dmaengine mac80211 aes_x86_64 snd_seq_midi lrw gf128mul glue_helper ablk_helper cryptd snd_seq_midi_event snd_rawmidi uvcvideo snd_hda_codec_realtek snd_hda_codec_generic videobuf2_vmalloc videobuf2_memops joydev snd_seq i915 videobuf2_core v4l2_common snd_hda_intel serio_raw snd_hda_controller videodev
[273529.409088]  snd_seq_device snd_hda_codec btusb snd_hwdep bluetooth media cfg80211 drm_kms_helper drm snd_pcm usbhid snd_timer mei_me i2c_algo_bit shpchp mei lpc_ich wmi snd i2c_hid soundcore hid snd_soc_sst_acpi dw_dmac int3400_thermal processor_thermal_device int3402_thermal acpi_thermal_rel dw_dmac_core 8250_dw i2c_designware_platform spi_pxa2xx_platform video i2c_designware_core intel_smartconnect mac_hid parport_pc ppdev lp parport autofs4 psmouse ahci libahci dm_mirror dm_region_hash dm_log sdhci_acpi sdhci [last unloaded: iwlwifi]
[273529.409135] CPU: 0 PID: 1865 Comm: Xorg Tainted: G        W      3.19.0-15-generic #15-Ubuntu
[273529.409138] Hardware name: ASUSTeK COMPUTER INC. UX301LAA/UX301LAA, BIOS UX301LAA.205 11/05/2013
[273529.409141]  ffffffffc064ae10 ffff88021465f9c8 ffffffff817c2205 0000000000000007
[273529.409145]  ffff88021465fa18 ffff88021465fa08 ffffffff8107595a 0000000000000000
[273529.409149]  0000000000000000 ffff8802141b3000 ffff880213160000 ffff880213160000
[273529.409154] Call Trace:
[273529.409165]  [<ffffffff817c2205>] dump_stack+0x45/0x57
[273529.409170]  [<ffffffff8107595a>] warn_slowpath_common+0x8a/0xc0
[273529.409174]  [<ffffffff810759d6>] warn_slowpath_fmt+0x46/0x50
[273529.409209]  [<ffffffffc05e752b>] assert_plane.constprop.87+0x7b/0x90 [i915]
[273529.409237]  [<ffffffffc05ef6a1>] hsw_disable_ips+0x41/0x190 [i915]
[273529.409265]  [<ffffffffc05efa68>] intel_crtc_disable_planes+0x48/0x140 [i915]
[273529.409289]  [<ffffffffc05f07cf>] haswell_crtc_disable+0x4f/0x3c0 [i915]
[273529.409313]  [<ffffffffc05f163c>] __intel_set_mode+0x92c/0xc80 [i915]
[273529.409320]  [<ffffffff811d650e>] ? __kmalloc+0x24e/0x280
[273529.409346]  [<ffffffffc05f77c8>] ? intel_crtc_set_config+0x88/0xf70 [i915]
[273529.409369]  [<ffffffffc05f7849>] ? intel_crtc_set_config+0x109/0xf70 [i915]
[273529.409392]  [<ffffffffc05f833b>] intel_crtc_set_config+0xbfb/0xf70 [i915]
[273529.409416]  [<ffffffffc029ee36>] drm_mode_set_config_internal+0x66/0x100 [drm]
[273529.409437]  [<ffffffffc02a30d3>] drm_mode_setcrtc+0x253/0x5a0 [drm]
[273529.409453]  [<ffffffffc0293a6f>] drm_ioctl+0x1df/0x680 [drm]
[273529.409460]  [<ffffffff81207b40>] do_vfs_ioctl+0x2e0/0x4e0
[273529.409465]  [<ffffffff811f5ae5>] ? __sb_end_write+0x35/0x70
[273529.409470]  [<ffffffff811f3552>] ? vfs_write+0x1b2/0x1f0
[273529.409475]  [<ffffffff81207dc1>] SyS_ioctl+0x81/0xa0
[273529.409479]  [<ffffffff81018099>] ? SyS_iopl+0x59/0xb0
[273529.409486]  [<ffffffff817c934d>] system_call_fastpath+0x16/0x1b
[273529.409490] ---[ end trace 8238d884482162ee ]---


After got the screens working again xrandr shows this info:
$ xrandr 
Screen 0: minimum 8 x 8, current 5280 x 1080, maximum 32767 x 32767
eDP1 connected 1920x1080+1440+0 (normal left inverted right x axis y axis) 294mm x 165mm
   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)
HDMI1 connected primary 1920x1080+3360+0 (normal left inverted right x axis y axis) 473mm x 296mm
   1680x1050      60.0 +
   1920x1080      60.0     50.0     59.9* 
   1920x1080i     60.1     50.0     60.0  
   1600x1200      60.0  
   1400x1050      59.9  
   1280x1024      75.0     60.0  
   1440x900       59.9  
   1360x768       59.8  
   1152x864       75.0  
   1280x720       60.0     50.0     59.9  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   720x576        50.0  
   720x576i       50.1  
   720x480        60.0     59.9  
   720x480i       60.1     60.1  
   640x480        75.0     72.8     66.7     60.0     59.9  
   720x400        70.1  
HDMI2 connected 1440x900+0+0 (normal left inverted right x axis y axis) 410mm x 257mm
   1440x900       59.9*+   75.0  
   1280x1024      75.0     60.0  
   1280x960       60.0  
   1152x864       75.0  
   1024x768       75.1     70.1     60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   640x480        75.0     72.8     66.7     60.0  
   720x400        70.1  
VIRTUAL1 disconnected (normal left inverted right x axis y axis)