Description of problem:
Thinkpad X240, no mains connection
Lid down -> switch to powersave -> invokes panel=off -> kernel bug

Additional info:
reporter:       libreport-2.2.3
WARNING: CPU: 1 PID: 3076 at drivers/gpu/drm/i915/intel_pm.c:6560 intel_display_power_put+0x130/0x160 [i915]()
Modules linked in: ccm hidp rfcomm ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 fuse xt_conntrack cpufreq_stats ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw bnep arc4 uvcvideo videobuf2_vmalloc videobuf2_core rtsx_pci_sdmmc videobuf2_memops v4l2_common videodev iTCO_wdt rtsx_pci_ms mmc_core memstick media iTCO_vendor_support btusb bluetooth cdc_acm snd_hda_codec_realtek iwlmvm snd_hda_codec_generic intel_rapl mac80211 snd_hda_codec_hdmi x86_pkg_temp_thermal coretemp snd_hda_intel snd_hda_controller snd_hda_codec kvm snd_hwdep snd_seq iwlwifi microcode snd_seq_device joydev cfg80211 serio_raw snd_pcm i2c_i801 rtsx_pci mei_me shpchp mei lpc_ich mfd_core snd_timer wmi thinkpad_acpi snd tpm_tis soundcore tpm rfkill nfsd auth_rpcgss nfs_acl lockd grace sunrpc dm_crypt crct10dif_pclmul crc32_pclmul crc32c_intel i915 i2c_algo_bit ghash_clmulni_intel drm_kms_helper e1000e ptp drm pps_core video cdc_mbim cdc_wdm cdc_ncm usbnet mii
CPU: 1 PID: 3076 Comm: kworker/1:1 Not tainted 3.18.9-100.fc20.x86_64 #1
Hardware name: LENOVO 20AL00C3GE/20AL00C3GE, BIOS GIET74WW (2.24 ) 05/13/2014
Workqueue: events edp_panel_vdd_work [i915]
 0000000000000000 000000000d2220df ffff88009ccf7d18 ffffffff81745f2b
 0000000000000000 0000000000000000 ffff88009ccf7d58 ffffffff81095061
 ffff88009ccf7d38 ffff88003608002c ffff8800369230e0 ffff880036088848
Call Trace:
 [<ffffffff81745f2b>] dump_stack+0x46/0x58
 [<ffffffff81095061>] warn_slowpath_common+0x81/0xa0
 [<ffffffff8109517a>] warn_slowpath_null+0x1a/0x20
 [<ffffffffa0119990>] intel_display_power_put+0x130/0x160 [i915]
 [<ffffffffa018906d>] pps_unlock+0x3d/0x50 [i915]
 [<ffffffffa018b2f9>] edp_panel_vdd_work+0x39/0x40 [i915]
 [<ffffffff810ada29>] process_one_work+0x149/0x3d0
 [<ffffffff810ae0ab>] worker_thread+0x11b/0x460
 [<ffffffff810adf90>] ? rescuer_thread+0x2e0/0x2e0
 [<ffffffff810b3238>] kthread+0xd8/0xf0
 [<ffffffff810b3160>] ? kthread_create_on_node+0x1b0/0x1b0
 [<ffffffff8174d2bc>] ret_from_fork+0x7c/0xb0
 [<ffffffff810b3160>] ? kthread_create_on_node+0x1b0/0x1b0