touchpad hang on 15.04 with Bios A04

When this happens, the touchpad becomes completely non-responsive. Nothing short of a reboot will restore function. Happens randomly and intermittently.  dmesg log with details below.

[ 2873.911652] ------------[ cut here ]------------
[ 2873.911681] WARNING: CPU: 1 PID: 3448 at /build/buildd/linux-3.19.0/drivers/gpu/drm/i915/intel_display.c:1256 assert_plane.constprop.87+0x7b/0x90 [i915]()
[ 2873.911683] plane A assertion failure (expected on, current off)
[ 2873.911684] Modules linked in: binfmt_misc hid_generic hidp pci_stub vboxpci(OE) vboxnetadp(OE) vboxnetflt(OE) vboxdrv(OE) rfcomm bnep uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_core usbhid v4l2_common btusb videodev bluetooth media joydev arc4 snd_hda_codec_hdmi dell_wmi sparse_keymap hid_multitouch dell_laptop dcdbas intel_rapl iosf_mbi x86_pkg_temp_thermal coretemp iwlmvm kvm_intel mac80211 kvm crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd iwlwifi serio_raw dell_led snd_hda_codec_realtek snd_hda_codec_generic rtsx_pci_ms memstick i915 cfg80211 drm_kms_helper lpc_ich snd_hda_intel shpchp snd_hda_controller snd_hda_codec drm snd_hwdep i2c_algo_bit wmi soc_button_array snd_soc_rt286 snd_soc_core int3403_thermal snd_compress
[ 2873.911709]  snd_pcm_dmaengine video snd_pcm snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq snd_seq_device snd_timer snd soundcore i2c_hid hid dw_dmac dw_dmac_core 8250_dw snd_soc_sst_acpi i2c_designware_platform i2c_designware_core processor_thermal_device spi_pxa2xx_platform mac_hid int3402_thermal int3400_thermal acpi_thermal_rel acpi_pad parport_pc ppdev lp parport autofs4 rtsx_pci_sdmmc ahci rtsx_pci libahci sdhci_acpi sdhci
[ 2873.911729] CPU: 1 PID: 3448 Comm: Xorg Tainted: G        W  OE  3.19.0-15-generic #15-Ubuntu
[ 2873.911730] Hardware name: Dell Inc. XPS 13 9343/0TM99H, BIOS A04 05/15/2015
[ 2873.911731]  ffffffffc0799e10 ffff8801e7d839c8 ffffffff817c2205 0000000000000007
[ 2873.911734]  ffff8801e7d83a18 ffff8801e7d83a08 ffffffff8107595a ffff8801e7d83fd8
[ 2873.911735]  0000000000000000 ffff8800c0fe6000 ffff88021515c000 ffff88021515c000
[ 2873.911737] Call Trace:
[ 2873.911745]  [ ] dump_stack+0x45/0x57
[ 2873.911747]  [ ] warn_slowpath_common+0x8a/0xc0
[ 2873.911749]  [ ] warn_slowpath_fmt+0x46/0x50
[ 2873.911765]  [ ] assert_plane.constprop.87+0x7b/0x90 [i915]
[ 2873.911778]  [ ] hsw_disable_ips+0x41/0x190 [i915]
[ 2873.911789]  [ ] intel_crtc_disable_planes+0x48/0x140 [i915]
[ 2873.911801]  [ ] haswell_crtc_disable+0x4f/0x3c0 [i915]
[ 2873.911812]  [ ] __intel_set_mode+0xa59/0xc80 [i915]
[ 2873.911824]  [ ] intel_crtc_set_config+0xbfb/0xf70 [i915]
[ 2873.911837]  [ ] drm_mode_set_config_internal+0x66/0x100 [drm]
[ 2873.911848]  [ ] drm_mode_setcrtc+0x253/0x5a0 [drm]
[ 2873.911855]  [ ] drm_ioctl+0x1df/0x680 [drm]
[ 2873.911859]  [ ] do_vfs_ioctl+0x2e0/0x4e0
[ 2873.911861]  [ ] ? __sb_end_write+0x35/0x70
[ 2873.911864]  [ ] ? vfs_write+0x1b2/0x1f0
[ 2873.911866]  [ ] SyS_ioctl+0x81/0xa0
[ 2873.911868]  [ ] ? SyS_iopl+0x59/0xb0
[ 2873.911871]  [ ] system_call_fastpath+0x16/0x1b
[ 2873.911873] ---[ end trace 4fd64b18b86bfabf ]---
[ 2875.144526] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun