FYI, we noticed the below changes on

git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
commit 51e31d49c89055299e34b8f44d13f70e19aaaad1 ("drm/i915: Use generic vblank wait")


+-------------------------+------------+------------+
|                         | 07f11d49f1 | 51e31d49c8 |
+-------------------------+------------+------------+
| boot_successes          | 10         | 0          |
| early-boot-hang         | 1          |            |
| boot_failures           | 0          | 3          |
| BUG:kernel_test_crashed | 0          | 3          |
+-------------------------+------------+------------+


<6>[   25.092524] ipmi message handler version 39.2
<6>[   25.106110] IPMI Watchdog: driver initialized
<4>[   46.024267] ------------[ cut here ]------------
<4>[   46.030029] WARNING: CPU: 0 PID: 1814 at drivers/gpu/drm/drm_irq.c:1080 drm_wait_one_vblank+0x180/0x190 [drm]()
<4>[   46.045334] vblank not available on crtc 1, ret=-22
<4>[   46.050710] Modules linked in: ipmi_watchdog ipmi_msghandler btrfs xor raid6_pq sg sr_mod sd_mod cdrom mxm_wmi pcspkr snd_hda_codec_hdmi snd_hda_codec_conexant snd_hda_codec_generic snd_hda_intel thinkpad_acpi snd_hda_controller i915 ahci snd_hda_codec sdhci_pci libahci snd_hwdep rfkill libata sdhci uvcvideo parport_pc parport videobuf2_vmalloc snd_pcm videobuf2_core firewire_ohci snd_timer videobuf2_memops mmc_core v4l2_common video i2c_i801 intel_ips drm_kms_helper firewire_core videodev snd crc_itu_t drm wmi soundcore acpi_cpufreq
<4>[   46.104497] CPU: 0 PID: 1814 Comm: kms_setmode Not tainted 3.18.0-rc2-g2d81df3 #1
<4>[   46.113099] Hardware name: LENOVO 25222AU/25222AU, BIOS 6IET52WW (1.12 ) 02/16/2010
<4>[   46.121968]  0000000000000009 ffff88006393f998 ffffffff81877998 ffff880066e0ffb8
<4>[   46.129736]  ffff88006393f9e8 ffff88006393f9d8 ffffffff8106a561 ffff88006393f9d8
<4>[   46.134783]  ffff8800755d0000 ffff8800766e3800 0000000000000001 0000000080000804
<4>[   46.138393] Call Trace:
<4>[   46.139060]  [<ffffffff81877998>] dump_stack+0x4e/0x68
<4>[   46.141227]  [<ffffffff8106a561>] warn_slowpath_common+0x81/0xa0
<4>[   46.144489]  [<ffffffff8106a5c6>] warn_slowpath_fmt+0x46/0x50
<4>[   46.146830]  [<ffffffffa004c7e0>] drm_wait_one_vblank+0x180/0x190 [drm]
<4>[   46.150249]  [<ffffffffa023d10b>] ? gen5_read32+0x5b/0xe0 [i915]
<4>[   46.152729]  [<ffffffffa027ef97>] intel_disable_hdmi+0x1a7/0x1e0 [i915]
<4>[   46.155166]  [<ffffffffa02541aa>] ironlake_crtc_disable+0x15a/0x7a0 [i915]
<4>[   46.158658]  [<ffffffff811bd83c>] ? kmem_cache_alloc_trace+0x4c/0x210
<4>[   46.161194]  [<ffffffffa025617b>] ? __intel_set_mode+0x4b/0xaf0 [i915]
<4>[   46.164606]  [<ffffffffa02563d7>] __intel_set_mode+0x2a7/0xaf0 [i915]
<4>[   46.167110]  [<ffffffffa025bdc6>] intel_set_mode+0x16/0x30 [i915]
<4>[   46.170410]  [<ffffffffa025cf52>] intel_crtc_set_config+0xa92/0xe90 [i915]
<4>[   46.173103]  [<ffffffff810904ca>] ? __might_sleep+0x3a/0xc0
<4>[   46.175309]  [<ffffffffa0054980>] drm_mode_set_config_internal+0x60/0xf0 [drm]
<4>[   46.178833]  [<ffffffffa0059053>] drm_mode_setcrtc+0x283/0x580 [drm]
<4>[   46.182285]  [<ffffffffa004a9d7>] drm_ioctl+0x197/0x680 [drm]
<4>[   46.184576]  [<ffffffff811f0e60>] do_vfs_ioctl+0x2f0/0x4f0
<4>[   46.186751]  [<ffffffff813958f7>] ? file_has_perm+0x87/0xa0
<4>[   46.189103]  [<ffffffff811f10e1>] SyS_ioctl+0x81/0xa0
<4>[   46.191292]  [<ffffffff81880369>] system_call_fastpath+0x12/0x17
<4>[   46.194522] ---[ end trace 7042ddb87f73ead7 ]---
<3>[   51.725259] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun