Comment 0 for bug 1301398

Since I've updated to 14.04 I'm unable to use a dual monitor setup.
When I connect the external monitor using an Apple VGA display port adapter both screens flicker and get garbled images.

Software info:

#uname -a
Linux ldavim-MacBookPro 3.13.0-21-generic #43-Ubuntu SMP Mon Mar 31 22:52:24 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

Hardware info:

#sudo dmidecode -s system-product-name
MacBookPro9,2

#lspci | grep -i vga
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)

#grep -i intel /var/log/Xorg.0.log | grep -i graphics
[ 28.392] (II) intel: Driver for Intel(R) Integrated Graphics Chipsets:
[ 28.409] (II) intel: Driver for Intel(R) HD Graphics: 2000-5000
[ 28.409] (II) intel: Driver for Intel(R) Iris(TM) Graphics: 5100
[ 28.409] (II) intel: Driver for Intel(R) Iris(TM) Pro Graphics: 5200
[ 28.493] (--) intel(0): Integrated Graphics Chipset: Intel(R) HD Graphics 4000

#dmesg | grep -i intel
[ 0.000000] Intel GenuineIntel
[ 0.083538] smpboot: CPU0: Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz (fam: 06, model: 3a, stepping: 09)
[ 0.085690] Performance Events: PEBS fmt1+, 16-deep LBR, IvyBridge events, full-width counters, Intel PMU driver.
[ 3.045095] intel_idle: MWAIT substates: 0x21120
[ 3.045096] intel_idle: v0.4 model 0x3A
[ 3.045097] intel_idle: lapic_timer_reliable_states 0xffffffff
[ 16.566496] fb: conflicting fb hw usage inteldrmfb vs EFI VGA - removing generic driver
[ 16.781552] fbcon: inteldrmfb (fb0) is primary device
[ 17.318068] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device
[ 17.329286] snd_hda_intel 0000:00:1b.0: enabling device (0000 -> 0002)
[ 17.329426] snd_hda_intel 0000:00:1b.0: irq 49 for MSI/MSI-X
[ 17.765675] intel_rapl: domain uncore energy ctr 15288:15288 not working, skip
[ 17.804152] input: HDA Intel PCH HDMI/DP,pcm=8 as /devices/pci0000:00/0000:00:1b.0/sound/card0/input12
[ 17.804214] input: HDA Intel PCH HDMI/DP,pcm=7 as /devices/pci0000:00/0000:00:1b.0/sound/card0/input11
[ 17.804258] input: HDA Intel PCH HDMI/DP,pcm=3 as /devices/pci0000:00/0000:00:1b.0/sound/card0/input10
[ 17.804300] input: HDA Intel PCH Headphone as /devices/pci0000:00/0000:00:1b.0/sound/card0/input9
[ 1908.293462] Modules linked in: hid_magicmouse hidp nvram pci_stub vboxpci(OF) vboxnetadp(OF) vboxnetflt(OF) vboxdrv(OF) cmac rmd160 crypto_null camellia_generic camellia_aesni_avx_x86_64 camellia_x86_64 cast6_avx_x86_64 cast6_generic cast5_avx_x86_64 cast5_generic cast_common deflate cts ctr gcm ccm serpent_avx_x86_64 serpent_sse2_x86_64 serpent_generic blowfish_generic blowfish_x86_64 blowfish_common twofish_generic twofish_avx_x86_64 twofish_x86_64_3way xts twofish_x86_64 twofish_common xcbc sha256_ssse3 sha512_ssse3 des_generic xfrm_user ah6 ah4 esp6 esp4 xfrm4_mode_beet xfrm4_tunnel tunnel4 xfrm4_mode_tunnel xfrm4_mode_transport xfrm6_mode_transport xfrm6_mode_ro xfrm6_mode_beet xfrm6_mode_tunnel ipcomp ipcomp6 xfrm6_tunnel tunnel6 xfrm_ipcomp af_key xfrm_algo btusb uvcvideo hid_appleir videobuf2_vmalloc videobuf2_memops bcm5974 videobuf2_core videodev bnep snd_hda_codec_hdmi rfcomm snd_hda_codec_cirrus intel_rapl x86_pkg_temp_thermal bluetooth intel_powerclamp coretemp snd_hda_intel joydev kvm_intel kvm snd_hda_codec applesmc input_polldev snd_hwdep snd_pcm i915 snd_page_alloc lib80211_crypt_tkip snd_seq_midi snd_seq_midi_event snd_rawmidi crct10dif_pclmul crc32_pclmul wl(POF) drm_kms_helper drm lib80211 ghash_clmulni_intel aesni_intel cfg80211 aes_x86_64 snd_seq mei_me lrw snd_seq_device dm_multipath gf128mul scsi_dh glue_helper snd_timer mei i2c_algo_bit lpc_ich ablk_helper snd cryptd soundcore apple_gmux mac_hid video apple_bl binfmt_misc lp parport hid_generic hid_apple usbhid hid ahci libahci firewire_ohci sdhci_pci dm_mirror firewire_core sdhci dm_region_hash crc_itu_t dm_log tg3 ptp pps_core