Could you try a 3.19 kernel? I can see at least the following there that may fix your issue:

commit 2c623c11c7d87ada0121c5502358b30c9a849d2d
Author: Egbert Eich <eich@suse.de>
Date:   Tue Nov 25 12:54:57 2014 +0100

    drm/i915/eDP: When enabling panel VDD cancel pending disable worker

If that doesn't fix the issue could you send a dmesg log up to the WARNs booting with drm.debug=14?

(In reply to Imre Deak from comment #1)
> Could you try a 3.19 kernel? I can see at least the following there that may
> fix your issue:
> 
> commit 2c623c11c7d87ada0121c5502358b30c9a849d2d
> Author: Egbert Eich <eich@suse.de>
> Date:   Tue Nov 25 12:54:57 2014 +0100
> 
>     drm/i915/eDP: When enabling panel VDD cancel pending disable worker
> 
> If that doesn't fix the issue could you send a dmesg log up to the WARNs
> booting with drm.debug=14?

I have downloaded the kernel from Fedora's updates-testing repo.

Will post more info once I've had a chance to reboot.

Rebooted into the updates-testing kernel (3.19.1-201.fc21) last night.

The problem (at least in my case) was usually quick to present, and I'm currently not seeing it.

That said, I've not undocked the laptop since I've rebooted it, and that might be one of the requisite trigger conditions...

Well, we can hope... please re-open if you see this again.

(In reply to Philip Prindeville from comment #3)
> Rebooted into the updates-testing kernel (3.19.1-201.fc21) last night.
> 
> The problem (at least in my case) was usually quick to present, and I'm
> currently not seeing it.
> 
> That said, I've not undocked the laptop since I've rebooted it, and that
> might be one of the requisite trigger conditions...

Definitely seems to be docking related.  Went out of town and took my laptop, then got back yesterday and docked again.  The problem immediately presented:

Apr  9 18:13:35 eng-dhcp-123 kernel: ------------[ cut here ]------------
Apr  9 18:13:35 eng-dhcp-123 kernel: WARNING: CPU: 0 PID: 3955 at drivers/gpu/drm/i915/intel_runtime_pm.c:676 intel_display_power_put+0x163/0x170 [i915]()
Apr  9 18:13:35 eng-dhcp-123 kernel: WARN_ON(!power_domains->domain_use_count[domain])
Apr  9 18:13:35 eng-dhcp-123 kernel: Modules linked in:
Apr  9 18:13:35 eng-dhcp-123 kernel: vhost_net vhost macvtap macvlan rfcomm fuse xt_CHECKSUM ipt_MASQUERADE nf_nat_masquerade_ipv4 tun nf_conntrack_netbios_ns nf_conntrack_broadcast ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 xt_conntrack 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 iwlmvm mac80211 dell_laptop intel_rapl iosf_mbi x86_pkg_temp_thermal coretemp dcdbas iTCO_wdt dell_wmi uvcvideo kvm_intel ppdev iTCO_vendor_support sparse_keymap i8k videobuf2_vmalloc kvm videobuf2_core snd_hda_codec_realtek crct10dif_pclmul crc32_pclmul iwlwifi snd_hda_codec_generic
Apr  9 18:13:35 eng-dhcp-123 kernel: snd_hda_codec_hdmi crc32c_intel videobuf2_memops btusb v4l2_common bluetooth videodev media snd_hda_intel snd_hda_controller snd_hda_codec snd_hwdep ghash_clmulni_intel snd_seq joydev sdhci_pci sdhci tpm_tis parport_pc serio_raw snd_seq_device cfg80211 snd_pcm snd_timer mmc_core parport i2c_i801 tpm snd lpc_ich rfkill mfd_core mei_me shpchp soundcore mei dell_smo8800 i915 nouveau ttm i2c_algo_bit drm_kms_helper drm e1000e ptp pps_core mxm_wmi wmi video
Apr  9 18:13:35 eng-dhcp-123 kernel: CPU: 0 PID: 3955 Comm: kworker/0:1 Tainted: G        W      3.19.1-201.fc21.x86_64 #1
Apr  9 18:13:35 eng-dhcp-123 kernel: Hardware name: Dell Inc. Latitude E5540/01389M, BIOS A04 01/22/2014
Apr  9 18:13:35 eng-dhcp-123 kernel: Workqueue: events edp_panel_vdd_work [i915]
Apr  9 18:13:35 eng-dhcp-123 kernel: 0000000000000000 00000000872944e9 ffff8800caf0bcc8 ffffffff8176d865
Apr  9 18:13:35 eng-dhcp-123 kernel: 0000000000000000 ffff8800caf0bd20 ffff8800caf0bd08 ffffffff8109bc0a
Apr  9 18:13:35 eng-dhcp-123 kernel: ffff8800caf0bce8 ffff8804182b002c ffff8804182b0000 ffff8804182b8980
Apr  9 18:13:35 eng-dhcp-123 kernel: Call Trace:
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffff8176d865>] dump_stack+0x45/0x57
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffff8109bc0a>] warn_slowpath_common+0x8a/0xc0
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffff8109bc95>] warn_slowpath_fmt+0x55/0x70
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffffa02d4bc0>] ? intel_display_power_put+0x120/0x170 [i915]
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffffa02d4c03>] intel_display_power_put+0x163/0x170 [i915]
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffffa034962d>] pps_unlock+0x3d/0x50 [i915]
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffffa034b989>] edp_panel_vdd_work+0x39/0x40 [i915]
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffff810b483c>] process_one_work+0x14c/0x3f0
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffff810b5203>] worker_thread+0x53/0x470
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffff810b51b0>] ? rescuer_thread+0x300/0x300
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffff810ba458>] kthread+0xd8/0xf0
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffff810ba380>] ? kthread_create_on_node+0x1b0/0x1b0
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffff81773f7c>] ret_from_fork+0x7c/0xb0
Apr  9 18:13:35 eng-dhcp-123 kernel: [<ffffffff810ba380>] ? kthread_create_on_node+0x1b0/0x1b0
Apr  9 18:13:35 eng-dhcp-123 kernel: ---[ end trace 76812c6edf03a9df ]---
Apr  9 18:13:36 eng-dhcp-123 abrt-dump-journal-oops: abrt-dump-journal-oops: Found oopses: 1
Apr  9 18:13:36 eng-dhcp-123 abrt-dump-journal-oops: abrt-dump-journal-oops: Creating problem directories
Apr  9 18:13:36 eng-dhcp-123 abrt-server: Deleting problem directory oops-2015-04-09-18:13:36-673-0 (dup of oops-2015-02-11-15:47:07-694-0)
Apr  9 18:13:36 eng-dhcp-123 gnome-session: abrt-applet: repeated problem in kernel, not showing the notification
Apr  9 18:13:37 eng-dhcp-123 abrt-dump-journal-oops: Reported 1 kernel oopses to Abrt

Could you provide a dmesg log booting with the drm.debug=14 kernel option, including the output from start of boot up to the WARN?

Created attachment 115010 [details]
messages log with drm.debug=14

(In reply to Philip Prindeville from comment #7)
> Created attachment 115010 [details]
> messages log with drm.debug=14

Hm, this doesn't include the output I expected, the kernel should output lot of  debug messages with the "[drm:func]" prefix with this kernel option. Are you maybe retrieving the log with some tool like journalctl that filters these messages out?

(In reply to Imre Deak from comment #8)
> (In reply to Philip Prindeville from comment #7)
> > Created attachment 115010 [details]
> > messages log with drm.debug=14
> 
> Hm, this doesn't include the output I expected, the kernel should output lot
> of  debug messages with the "[drm:func]" prefix with this kernel option. Are
> you maybe retrieving the log with some tool like journalctl that filters
> these messages out?

No, that's the contents of my /var/log/messages* files for the range that you requested.

Is it possible that the DRM module got built with the debugging code turned off?

(In reply to Philip Prindeville from comment #9)
> (In reply to Imre Deak from comment #8)
> > (In reply to Philip Prindeville from comment #7)
> > > Created attachment 115010 [details]
> > > messages log with drm.debug=14
> > 
> > Hm, this doesn't include the output I expected, the kernel should output lot
> > of  debug messages with the "[drm:func]" prefix with this kernel option. Are
> > you maybe retrieving the log with some tool like journalctl that filters
> > these messages out?
> 
> No, that's the contents of my /var/log/messages* files for the range that
> you requested.
> 
> Is it possible that the DRM module got built with the debugging code turned
> off?

No, unless you have some custom/distro specific patch that would disable it. The driver in the upstream kernel is always built to emit the debug messages if drm.debug is set. But your syslog daemon may be configured to write kernel messages above a certain loglevel to a separate file like /var/log/kern.log or /var/log/debug.log, please check /etc/rsyslogd (or similar). You can also check if these messages are really emitted by just running dmesg (but the output of this is probably truncated, so it won't do).

Created attachment 115940 [details]
dmesg with drm.debug=14 log_buf_len=16M

Hello,
this is what I did to recreate the bug:
My Laptop is with dockingstation.
I have the same problem with kernels from 3.16 to 3.18
1. Start the laptop without attached to dock station.
2. Connect to the dock station
3. Disconnect from dock station
4. Connect to the dock station and I get the "WARNING: CPU: 0 PID: 6522 at drivers/gpu/drm/i915/intel_pm.c:6560 intel_display_power_put+0x43/0xfa [i915]()"
5. Restart xorg

I added attachment with dmesg log

Could you please try a newer kernel? Ideally the drm-intel-nightly branch from [1] or at least version 4.0.

    [1] http://cgit.freedesktop.org/drm-intel

Tried with 4.0.4 - same problem.

I think fixes have gone in to address this, please try v4.9 or v4.10-rc1.

Fixes has been placed according to Jani on v4.9 or v4.10-rc1, please upgrade the kernel.
I'm placing the bug as resolved but please if you encounter the issue after those versions of Kernel reopen the bug

otherwise please close it