Description of problem:
I'm not sure what caused this: it seems to happen during boot or when the display wakes up.  It may be closely linked to a DisplayPort connection (as opposed to DVI or VGA).

Additional info:
reporter:       libreport-2.3.0
WARNING: CPU: 2 PID: 6 at drivers/gpu/drm/i915/intel_display.c:901 intel_wait_for_vblank+0x225/0x230 [i915]()
vblank wait on pipe B timed out
Modules linked in: i915(+) crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel e1000e i2c_algo_bit drm_kms_helper drm firewire_ohci ptp firewire_core pps_core crc_itu_t video hid_logitech_dj
CPU: 2 PID: 6 Comm: kworker/u16:0 Not tainted 3.18.3-201.fc21.x86_64 #1
Hardware name: Dell Inc. Latitude E6410/0667CC, BIOS A07 02/15/2011
Workqueue: events_unbound async_run_entry_fn
 0000000000000000 00000000062be7e8 ffff8802141af618 ffffffff8175da66
 0000000000000000 ffff8802141af670 ffff8802141af658 ffffffff81099181
 0000000000000000 ffff880211560000 0000000000071040 0000000000000001
Call Trace:
 [<ffffffff8175da66>] dump_stack+0x46/0x58
 [<ffffffff81099181>] warn_slowpath_common+0x81/0xa0
 [<ffffffff810991f5>] warn_slowpath_fmt+0x55/0x70
 [<ffffffffa0180175>] intel_wait_for_vblank+0x225/0x230 [i915]
 [<ffffffffa01a2f5d>] intel_dp_link_down+0x1ad/0x250 [i915]
 [<ffffffffa01a3442>] ilk_post_disable_dp+0x22/0xf0 [i915]
 [<ffffffffa018ac24>] ironlake_crtc_disable+0xe4/0x7b0 [i915]
 [<ffffffffa017c4bc>] ? intel_dump_pipe_config.isra.51+0x3c/0x3c0 [i915]
 [<ffffffffa0184e41>] __intel_set_mode+0x7f1/0x16f0 [i915]
 [<ffffffffa018dc36>] intel_set_mode+0x16/0x30 [i915]
 [<ffffffffa018edda>] intel_crtc_set_config+0xa9a/0xea0 [i915]
 [<ffffffff8138ffd6>] ? get_from_free_list+0x46/0x60
 [<ffffffffa0061e30>] drm_mode_set_config_internal+0x60/0xf0 [drm]
 [<ffffffffa00bd553>] restore_fbdev_mode+0xd3/0x100 [drm_kms_helper]
 [<ffffffffa00bf099>] drm_fb_helper_restore_fbdev_mode_unlocked+0x29/0x80 [drm_kms_helper]
 [<ffffffffa00bf112>] drm_fb_helper_set_par+0x22/0x50 [drm_kms_helper]
 [<ffffffffa0199efa>] intel_fbdev_set_par+0x1a/0x60 [i915]
 [<ffffffff813fbe88>] fbcon_init+0x578/0x600
 [<ffffffff8147a0bc>] visual_init+0xbc/0x120
 [<ffffffff8147c88e>] do_bind_con_driver+0x17e/0x3b0
 [<ffffffff8147d064>] do_take_over_console+0xb4/0x1b0
 [<ffffffff813f6c63>] do_fbcon_takeover+0x63/0xd0
 [<ffffffff813fc9ad>] fbcon_event_notify+0x6cd/0x7d0
 [<ffffffff810b8fdd>] notifier_call_chain+0x4d/0x80
 [<ffffffff810b935b>] __blocking_notifier_call_chain+0x4b/0x70
 [<ffffffff810b9396>] blocking_notifier_call_chain+0x16/0x20
 [<ffffffff8140291b>] fb_notifier_call_chain+0x1b/0x20
 [<ffffffff81404cf4>] register_framebuffer+0x214/0x360
 [<ffffffffa00bf3af>] drm_fb_helper_initial_config+0x26f/0x3d0 [drm_kms_helper]
 [<ffffffff81012651>] ? __switch_to+0x151/0x5f0
 [<ffffffffa019b1ab>] intel_fbdev_initial_config+0x1b/0x20 [i915]
 [<ffffffff810bab8a>] async_run_entry_fn+0x4a/0x150
 [<ffffffff810b240d>] process_one_work+0x14d/0x400
 [<ffffffff810b2d9b>] worker_thread+0x6b/0x4a0
 [<ffffffff810b2d30>] ? rescuer_thread+0x2a0/0x2a0
 [<ffffffff810b7fea>] kthread+0xea/0x100
 [<ffffffff810b7f00>] ? kthread_create_on_node+0x1b0/0x1b0
 [<ffffffff817646fc>] ret_from_fork+0x7c/0xb0
 [<ffffffff810b7f00>] ? kthread_create_on_node+0x1b0/0x1b0