Additional info:
reporter:       libreport-2.3.0
WARNING: CPU: 1 PID: 57 at drivers/gpu/drm/drm_irq.c:1121 drm_wait_one_vblank+0x190/0x1a0 [drm]()
vblank not available on crtc 0, ret=-22
Modules linked in: i915 i2c_algo_bit drm_kms_helper drm video ata_generic pata_acpi
CPU: 1 PID: 57 Comm: kworker/u4:2 Not tainted 3.19.3-200.fc21.x86_64 #1
Hardware name: Apple Inc. MacBookAir1,1/Mac-F42C8CC8, BIOS    MBA11.88Z.00BB.B03.0803171226 03/17/08
Workqueue: events_unbound async_run_entry_fn
 0000000000000000 000000002253836d ffff88003f917768 ffffffff8176e215
 0000000000000000 ffff88003f9177c0 ffff88003f9177a8 ffffffff8109bc1a
 ffff88003f9177c8 ffff880077010000 ffff88003f5fd000 0000000000000000
Call Trace:
 [<ffffffff8176e215>] dump_stack+0x45/0x57
 [<ffffffff8109bc1a>] warn_slowpath_common+0x8a/0xc0
 [<ffffffff8109bca5>] warn_slowpath_fmt+0x55/0x70
 [<ffffffff8177444a>] ? _raw_spin_lock_irqsave+0xa/0x60
 [<ffffffffa0024930>] drm_wait_one_vblank+0x190/0x1a0 [drm]
 [<ffffffffa00f584f>] ? gen4_read32+0x4f/0xc0 [i915]
 [<ffffffffa0149b95>] intel_enable_tv+0x25/0x60 [i915]
 [<ffffffffa0112c4b>] i9xx_crtc_enable+0x3fb/0x4c0 [i915]
 [<ffffffffa01111c2>] __intel_set_mode+0x8a2/0xca0 [i915]
 [<ffffffffa011736c>] intel_set_mode+0x7c/0xc0 [i915]
 [<ffffffffa010226c>] ? intel_framebuffer_init+0x31c/0x440 [i915]
 [<ffffffffa0117636>] intel_get_load_detect_pipe+0x286/0x620 [i915]
 [<ffffffffa014a794>] intel_tv_detect+0x134/0x5d0 [i915]
 [<ffffffff81100c30>] ? internal_add_timer+0xb0/0xb0
 [<ffffffffa0084c03>] drm_helper_probe_single_connector_modes_merge_bits+0x303/0x460 [drm_kms_helper]
 [<ffffffffa0084d73>] drm_helper_probe_single_connector_modes+0x13/0x20 [drm_kms_helper]
 [<ffffffffa008ebb0>] drm_fb_helper_probe_connector_modes.isra.3+0x50/0x70 [drm_kms_helper]
 [<ffffffffa008ffdc>] drm_fb_helper_initial_config+0x5c/0x3d0 [drm_kms_helper]
 [<ffffffff81013610>] ? __switch_to+0x150/0x5e0
 [<ffffffffa0126fdb>] intel_fbdev_initial_config+0x1b/0x20 [i915]
 [<ffffffff810bd06a>] async_run_entry_fn+0x4a/0x150
 [<ffffffff810b487c>] process_one_work+0x14c/0x3f0
 [<ffffffff810b52f3>] worker_thread+0x53/0x470
 [<ffffffff810b52a0>] ? rescuer_thread+0x300/0x300
 [<ffffffff810ba548>] kthread+0xd8/0xf0
 [<ffffffff810ba470>] ? kthread_create_on_node+0x1b0/0x1b0
 [<ffffffff81774958>] ret_from_fork+0x58/0x90
 [<ffffffff810ba470>] ? kthread_create_on_node+0x1b0/0x1b0

Potential duplicate: bug 1210101