Fedora 27 with 4.13.2, mesa 7.2.0 and gnome 3.26, we get a series of crashes in drm_atomic_helper_wait_for_vblanks during the early boot process while X/wayland/gdm is starting up, and sometimes during use, although I'm not testing using thoroughly atm. There seems to be a couple of variations of the crash so I've included them all.
[ 53.750617] ------------[ cut here ]------------
[ 53.750743] WARNING: CPU: 1 PID: 461 at drivers/gpu/drm/drm_atomic_helper.c:1236 drm_atomic_helper_wait_for_vblanks+0xe0/0x1f4 [drm_kms_helper]
[ 53.750750] [CRTC:66:crtc-2] vblank wait timed out
[ 53.750754] Modules linked in: vc4(+) snd_soc_core ac97_bus snd_pcm_dmaengine snd_seq snd_seq_device snd_pcm hci_uart brcmfmac btbcm btqca brcmutil btintel snd_timer cfg80211 bluetooth snd soundcore drm_kms_helper ecdh_generic rfkill drm fb_sys_fops syscopyarea sysfillrect sysimgblt bcm2835_wdt bcm2835_thermal bcm2835_rng leds_gpio smsc95xx usbnet mii mmc_block sdhci_iproc sdhci_pltfm crc32_arm_ce dwc2 udc_core sdhci pwm_bcm2835 bcm2835 i2c_bcm2835 bcm2835_dma phy_generic
[ 53.750942] CPU: 1 PID: 461 Comm: systemd-udevd Tainted: G W 4.13.2-300.fc27.armv7hl #1
[ 53.750947] Hardware name: Generic DT based system
[ 53.750966] [] (unwind_backtrace) from [] (show_stack+0x18/0x1c)
[ 53.750981] [] (show_stack) from [] (dump_stack+0xa0/0xd8)
[ 53.750996] [] (dump_stack) from [] (__warn+0xe4/0x104)
[ 53.751009] [] (__warn) from [] (warn_slowpath_fmt+0x3c/0x4c)
[ 53.751137] [] (warn_slowpath_fmt) from [] (drm_atomic_helper_wait_for_vblanks+0xe0/0x1f4 [drm_kms_helper])
[ 53.751342] [] (drm_atomic_helper_wait_for_vblanks [drm_kms_helper]) from [] (vc4_atomic_complete_commit+0x7c/0xbc [vc4])
[ 53.751510] [] (vc4_atomic_complete_commit [vc4]) from [] (vc4_atomic_commit+0x180/0x190 [vc4])
[ 53.751711] [] (vc4_atomic_commit [vc4]) from [] (restore_fbdev_mode+0x94/0x24c [drm_kms_helper])
[ 53.751953] [] (restore_fbdev_mode [drm_kms_helper]) from [] (drm_fb_helper_restore_fbdev_mode_unlocked+0x38/0x70 [drm_kms_helper])
[ 53.752192] [] (drm_fb_helper_restore_fbdev_mode_unlocked [drm_kms_helper]) from [] (drm_fb_helper_set_par+0x54/0x64 [drm_kms_helper])
[ 53.752320] [] (drm_fb_helper_set_par [drm_kms_helper]) from [] (fbcon_init+0x2cc/0x454)
[ 53.752336] [] (fbcon_init) from [] (visual_init+0xc8/0x118)
[ 53.752351] [] (visual_init) from [] (do_bind_con_driver+0x26c/0x2dc)
[ 53.752366] [] (do_bind_con_driver) from [] (do_take_over_console+0x174/0x1a8)
[ 53.752381] [] (do_take_over_console) from [] (do_fbcon_takeover+0x58/0xc0)
[ 53.752397] [] (do_fbcon_takeover) from [] (notifier_call_chain+0x84/0xb0)
[ 53.752413] [] (notifier_call_chain) from [] (__blocking_notifier_call_chain+0x48/0x60)
[ 53.752429] [] (__blocking_notifier_call_chain) from [] (blocking_notifier_call_chain+0x1c/0x24)
[ 53.752443] [] (blocking_notifier_call_chain) from [] (register_framebuffer+0x234/0x278)
[ 53.752569] [] (register_framebuffer) from [] (drm_fb_helper_initial_config+0x1c0/0x3a8 [drm_kms_helper])
[ 53.752807] [] (drm_fb_helper_initial_config [drm_kms_helper]) from [] (drm_fbdev_cma_init_with_funcs+0xb8/0xf4 [drm_kms_helper])
[ 53.753008] [] (drm_fbdev_cma_init_with_funcs [drm_kms_helper]) from [] (vc4_kms_load+0xd0/0x108 [vc4])
[ 53.753175] [] (vc4_kms_load [vc4]) from [] (vc4_drm_bind+0xe4/0x128 [vc4])
[ 53.753268] [] (vc4_drm_bind [vc4]) from [] (try_to_bring_up_master+0x1ec/0x254)
[ 53.753285] [] (try_to_bring_up_master) from [] (component_master_add_with_match+0xc0/0xec)
[ 53.753376] [] (component_master_add_with_match) from [] (vc4_platform_drm_probe+0x74/0xb0 [vc4])
[ 53.753469] [] (vc4_platform_drm_probe [vc4]) from [] (platform_drv_probe+0x58/0xa4)
[ 53.753484] [] (platform_drv_probe) from [] (driver_probe_device+0x28c/0x424)
[ 53.753498] [] (driver_probe_device) from [] (__driver_attach+0x90/0x100)
[ 53.753513] [] (__driver_attach) from [] (bus_for_each_dev+0x84/0x94)
[ 53.753531] [] (bus_for_each_dev) from [] (bus_add_driver+0x1bc/0x234)
[ 53.753547] [] (bus_add_driver) from [] (driver_register+0xa8/0xe8)
[ 53.753562] [] (driver_register) from [] (do_one_initcall+0x130/0x158)
[ 53.753578] [] (do_one_initcall) from [] (do_init_module+0x60/0x1dc)
[ 53.753593] [] (do_init_module) from [] (load_module+0x2430/0x24d8)
[ 53.753609] [] (load_module) from [] (SyS_finit_module+0xb0/0xc4)
[ 53.753626] [] (SyS_finit_module) from [] (__sys_trace_return+0x0/0x10)
[ 53.753670] ---[ end trace b2e9be4e1ce19772 ]---
[ 63.987758] [drm:drm_atomic_helper_commit_cleanup_done [drm_kms_helper]] *ERROR* [CRTC:66:crtc-2] flip_done timed out
[ 63.987947] Console: switching to colour frame buffer device 240x75
[ 64.038622] ------------[ cut here ]------------
[ 64.038753] WARNING: CPU: 1 PID: 461 at drivers/gpu/drm/drm_atomic_helper.c:1236 drm_atomic_helper_wait_for_vblanks+0xe0/0x1f4 [drm_kms_helper]
[ 64.038760] [CRTC:66:crtc-2] vblank wait timed out
[ 64.038765] Modules linked in: vc4(+) snd_soc_core ac97_bus snd_pcm_dmaengine snd_seq snd_seq_device snd_pcm hci_uart brcmfmac btbcm btqca brcmutil btintel snd_timer cfg80211 bluetooth snd soundcore drm_kms_helper ecdh_generic rfkill drm fb_sys_fops syscopyarea sysfillrect sysimgblt bcm2835_wdt bcm2835_thermal bcm2835_rng leds_gpio smsc95xx usbnet mii mmc_block sdhci_iproc sdhci_pltfm crc32_arm_ce dwc2 udc_core sdhci pwm_bcm2835 bcm2835 i2c_bcm2835 bcm2835_dma phy_generic
[ 64.038968] CPU: 1 PID: 461 Comm: systemd-udevd Tainted: G W 4.13.2-300.fc27.armv7hl #1
[ 64.038973] Hardware name: Generic DT based system
[ 64.039002] [] (unwind_backtrace) from [] (show_stack+0x18/0x1c)
[ 64.039020] [] (show_stack) from [] (dump_stack+0xa0/0xd8)
[ 64.039037] [] (dump_stack) from [] (__warn+0xe4/0x104)
[ 64.039052] [] (__warn) from [] (warn_slowpath_fmt+0x3c/0x4c)
[ 64.039180] [] (warn_slowpath_fmt) from [] (drm_atomic_helper_wait_for_vblanks+0xe0/0x1f4 [drm_kms_helper])
[ 64.039399] [] (drm_atomic_helper_wait_for_vblanks [drm_kms_helper]) from [] (vc4_atomic_complete_commit+0x7c/0xbc [vc4])
[ 64.039568] [] (vc4_atomic_complete_commit [vc4]) from [] (vc4_atomic_commit+0x180/0x190 [vc4])
[ 64.039769] [] (vc4_atomic_commit [vc4]) from [] (drm_fb_helper_pan_display+0xa8/0x1d8 [drm_kms_helper])
[ 64.039902] [] (drm_fb_helper_pan_display [drm_kms_helper]) from [] (fb_pan_display+0xf4/0x130)
[ 64.039924] [] (fb_pan_display) from [] (bit_update_start+0x1c/0x38)
[ 64.039942] [] (bit_update_start) from [] (fbcon_switch+0x3b4/0x46c)
[ 64.039960] [] (fbcon_switch) from [] (redraw_screen+0x104/0x1d8)
[ 64.039976] [] (redraw_screen) from [] (do_bind_con_driver+0x184/0x2dc)
[ 64.039991] [] (do_bind_con_driver) from [] (do_take_over_console+0x174/0x1a8)
[ 64.040007] [] (do_take_over_console) from [] (do_fbcon_takeover+0x58/0xc0)
[ 64.040024] [] (do_fbcon_takeover) from [] (notifier_call_chain+0x84/0xb0)
[ 64.040041] [] (notifier_call_chain) from [] (__blocking_notifier_call_chain+0x48/0x60)
[ 64.040057] [] (__blocking_notifier_call_chain) from [] (blocking_notifier_call_chain+0x1c/0x24)
[ 64.040072] [] (blocking_notifier_call_chain) from [] (register_framebuffer+0x234/0x278)
[ 64.040197] [] (register_framebuffer) from [] (drm_fb_helper_initial_config+0x1c0/0x3a8 [drm_kms_helper])
[ 64.040436] [] (drm_fb_helper_initial_config [drm_kms_helper]) from [] (drm_fbdev_cma_init_with_funcs+0xb8/0xf4 [drm_kms_helper])
[ 64.040639] [] (drm_fbdev_cma_init_with_funcs [drm_kms_helper]) from [] (vc4_kms_load+0xd0/0x108 [vc4])
[ 64.040806] [] (vc4_kms_load [vc4]) from [] (vc4_drm_bind+0xe4/0x128 [vc4])
[ 64.040901] [] (vc4_drm_bind [vc4]) from [] (try_to_bring_up_master+0x1ec/0x254)
[ 64.040919] [] (try_to_bring_up_master) from [] (component_master_add_with_match+0xc0/0xec)
[ 64.041010] [] (component_master_add_with_match) from [] (vc4_platform_drm_probe+0x74/0xb0 [vc4])
[ 64.041104] [] (vc4_platform_drm_probe [vc4]) from [] (platform_drv_probe+0x58/0xa4)
[ 64.041120] [] (platform_drv_probe) from [] (driver_probe_device+0x28c/0x424)
[ 64.041135] [] (driver_probe_device) from [] (__driver_attach+0x90/0x100)
[ 64.041150] [] (__driver_attach) from [] (bus_for_each_dev+0x84/0x94)
[ 64.041169] [] (bus_for_each_dev) from [] (bus_add_driver+0x1bc/0x234)
[ 64.041185] [] (bus_add_driver) from [] (driver_register+0xa8/0xe8)
[ 64.041200] [] (driver_register) from [] (do_one_initcall+0x130/0x158)
[ 64.041219] [] (do_one_initcall) from [] (do_init_module+0x60/0x1dc)
[ 64.041237] [] (do_init_module) from [] (load_module+0x2430/0x24d8)
[ 64.041253] [] (load_module) from [] (SyS_finit_module+0xb0/0xc4)
[ 64.041271] [] (SyS_finit_module) from [] (__sys_trace_return+0x0/0x10)
[ 64.041321] ---[ end trace b2e9be4e1ce19773 ]---
[ 74.227770] [drm:drm_atomic_helper_commit_cleanup_done [drm_kms_helper]] *ERROR* [CRTC:66:crtc-2] flip_done timed out
[ 77.455914] vc4-drm soc:gpu: fb0: frame buffer device
[ 77.529634] ------------[ cut here ]------------
[ 77.529781] WARNING: CPU: 2 PID: 504 at drivers/gpu/drm/drm_atomic_helper.c:1236 drm_atomic_helper_wait_for_vblanks+0xe0/0x1f4 [drm_kms_helper]
[ 77.529794] [CRTC:66:crtc-2] vblank wait timed out
[ 77.529798] Modules linked in: vc4 snd_soc_core ac97_bus snd_pcm_dmaengine snd_seq snd_seq_device snd_pcm hci_uart brcmfmac btbcm btqca brcmutil btintel snd_timer cfg80211 bluetooth snd soundcore drm_kms_helper ecdh_generic rfkill drm fb_sys_fops syscopyarea sysfillrect sysimgblt bcm2835_wdt bcm2835_thermal bcm2835_rng leds_gpio smsc95xx usbnet mii mmc_block sdhci_iproc sdhci_pltfm crc32_arm_ce dwc2 udc_core sdhci pwm_bcm2835 bcm2835 i2c_bcm2835 bcm2835_dma phy_generic
[ 77.530008] CPU: 2 PID: 504 Comm: setfont Tainted: G W 4.13.2-300.fc27.armv7hl #1
[ 77.530013] Hardware name: Generic DT based system
[ 77.530046] [] (unwind_backtrace) from [] (show_stack+0x18/0x1c)
[ 77.530064] [] (show_stack) from [] (dump_stack+0xa0/0xd8)
[ 77.530082] [] (dump_stack) from [] (__warn+0xe4/0x104)
[ 77.530096] [] (__warn) from [] (warn_slowpath_fmt+0x3c/0x4c)
[ 77.530228] [] (warn_slowpath_fmt) from [] (drm_atomic_helper_wait_for_vblanks+0xe0/0x1f4 [drm_kms_helper])
[ 77.530430] [] (drm_atomic_helper_wait_for_vblanks [drm_kms_helper]) from [] (vc4_atomic_complete_commit+0x7c/0xbc [vc4])
[ 77.530573] [] (vc4_atomic_complete_commit [vc4]) from [] (vc4_atomic_commit+0x180/0x190 [vc4])
[ 77.530766] [] (vc4_atomic_commit [vc4]) from [] (drm_fb_helper_pan_display+0xa8/0x1d8 [drm_kms_helper])
[ 77.530901] [] (drm_fb_helper_pan_display [drm_kms_helper]) from [] (fb_pan_display+0xf4/0x130)
[ 77.530923] [] (fb_pan_display) from [] (bit_update_start+0x1c/0x38)
[ 77.530941] [] (bit_update_start) from [] (fbcon_switch+0x3b4/0x46c)
[ 77.530959] [] (fbcon_switch) from [] (redraw_screen+0x104/0x1d8)
[ 77.530976] [] (redraw_screen) from [] (fbcon_do_set_font+0x1e8/0x1f8)
[ 77.530994] [] (fbcon_do_set_font) from [] (fbcon_set_font+0x1e8/0x230)
[ 77.531010] [] (fbcon_set_font) from [] (con_font_op+0x1a8/0x4b0)
[ 77.531027] [] (con_font_op) from [] (vt_ioctl+0x1668/0x16fc)
[ 77.531045] [] (vt_ioctl) from [] (tty_ioctl+0x9c0/0xa78)
[ 77.531063] [] (tty_ioctl) from [] (vfs_ioctl+0x28/0x3c)
[ 77.531078] [] (vfs_ioctl) from [] (do_vfs_ioctl+0x9c/0x968)
[ 77.531093] [] (do_vfs_ioctl) from [] (SyS_ioctl+0x58/0x74)
[ 77.531110] [] (SyS_ioctl) from [] (__sys_trace_return+0x0/0x10)
[ 77.531165] ---[ end trace b2e9be4e1ce19774 ]---
[ 87.539766] [drm:drm_atomic_helper_commit_cleanup_done [drm_kms_helper]] *ERROR* [CRTC:66:crtc-2] flip_done timed out
[ 87.616616] ------------[ cut here ]------------
[ 87.616756] WARNING: CPU: 1 PID: 34 at drivers/gpu/drm/drm_atomic_helper.c:1236 drm_atomic_helper_wait_for_vblanks+0xe0/0x1f4 [drm_kms_helper]
[ 87.616763] [CRTC:66:crtc-2] vblank wait timed out
[ 87.616768] Modules linked in: vc4 snd_soc_core ac97_bus snd_pcm_dmaengine snd_seq snd_seq_device snd_pcm hci_uart brcmfmac btbcm btqca brcmutil btintel snd_timer cfg80211 bluetooth snd soundcore drm_kms_helper ecdh_generic rfkill drm fb_sys_fops syscopyarea sysfillrect sysimgblt bcm2835_wdt bcm2835_thermal bcm2835_rng leds_gpio smsc95xx usbnet mii mmc_block sdhci_iproc sdhci_pltfm crc32_arm_ce dwc2 udc_core sdhci pwm_bcm2835 bcm2835 i2c_bcm2835 bcm2835_dma phy_generic
[ 87.616976] CPU: 1 PID: 34 Comm: kworker/1:1 Tainted: G W 4.13.2-300.fc27.armv7hl #1
[ 87.616981] Hardware name: Generic DT based system
[ 87.617106] Workqueue: events output_poll_execute [drm_kms_helper]
[ 87.617139] [] (unwind_backtrace) from [] (show_stack+0x18/0x1c)
[ 87.617156] [] (show_stack) from [] (dump_stack+0xa0/0xd8)
[ 87.617173] [] (dump_stack) from [] (__warn+0xe4/0x104)
[ 87.617188] [] (__warn) from [] (warn_slowpath_fmt+0x3c/0x4c)
[ 87.617314] [] (warn_slowpath_fmt) from [] (drm_atomic_helper_wait_for_vblanks+0xe0/0x1f4 [drm_kms_helper])
[ 87.617513] [] (drm_atomic_helper_wait_for_vblanks [drm_kms_helper]) from [] (vc4_atomic_complete_commit+0x7c/0xbc [vc4])
[ 87.617657] [] (vc4_atomic_complete_commit [vc4]) from [] (vc4_atomic_commit+0x180/0x190 [vc4])
[ 87.617846] [] (vc4_atomic_commit [vc4]) from [] (restore_fbdev_mode+0x94/0x24c [drm_kms_helper])
[ 87.618084] [] (restore_fbdev_mode [drm_kms_helper]) from [] (drm_fb_helper_restore_fbdev_mode_unlocked+0x38/0x70 [drm_kms_helper])
[ 87.618323] [] (drm_fb_helper_restore_fbdev_mode_unlocked [drm_kms_helper]) from [] (drm_fb_helper_set_par+0x54/0x64 [drm_kms_helper])
[ 87.618562] [] (drm_fb_helper_set_par [drm_kms_helper]) from [] (drm_fb_helper_hotplug_event+0x9c/0xac [drm_kms_helper])
[ 87.618798] [] (drm_fb_helper_hotplug_event [drm_kms_helper]) from [] (output_poll_execute+0x174/0x188 [drm_kms_helper])
[ 87.618927] [] (output_poll_execute [drm_kms_helper]) from [] (process_one_work+0x43c/0x83c)
[ 87.618942] [] (process_one_work) from [] (worker_thread+0x290/0x40c)
[ 87.618961] [] (worker_thread) from [] (kthread+0x14c/0x168)
[ 87.618981] [] (kthread) from [] (ret_from_fork+0x14/0x24)
[ 87.619025] ---[ end trace b2e9be4e1ce19775 ]---
[ 97.779746] [drm:drm_atomic_helper_commit_cleanup_done [drm_kms_helper]] *ERROR* [CRTC:66:crtc-2] flip_done timed out
[ 99.922634] ------------[ cut here ]------------
[ 99.922779] WARNING: CPU: 0 PID: 518 at drivers/gpu/drm/drm_atomic_helper.c:1236 drm_atomic_helper_wait_for_vblanks+0xe0/0x1f4 [drm_kms_helper]
[ 99.922798] [CRTC:66:crtc-2] vblank wait timed out
[ 99.922803] Modules linked in: vc4 snd_soc_core ac97_bus snd_pcm_dmaengine snd_seq snd_seq_device snd_pcm hci_uart brcmfmac btbcm btqca brcmutil btintel snd_timer cfg80211 bluetooth snd soundcore drm_kms_helper ecdh_generic rfkill drm fb_sys_fops syscopyarea sysfillrect sysimgblt bcm2835_wdt bcm2835_thermal bcm2835_rng leds_gpio smsc95xx usbnet mii mmc_block sdhci_iproc sdhci_pltfm crc32_arm_ce dwc2 udc_core sdhci pwm_bcm2835 bcm2835 i2c_bcm2835 bcm2835_dma phy_generic
[ 99.923031] CPU: 0 PID: 518 Comm: setfont Tainted: G W 4.13.2-300.fc27.armv7hl #1
[ 99.923037] Hardware name: Generic DT based system
[ 99.923070] [] (unwind_backtrace) from [] (show_stack+0x18/0x1c)
[ 99.923087] [] (show_stack) from [] (dump_stack+0xa0/0xd8)
[ 99.923105] [] (dump_stack) from [] (__warn+0xe4/0x104)
[ 99.923120] [] (__warn) from [] (warn_slowpath_fmt+0x3c/0x4c)
[ 99.923246] [] (warn_slowpath_fmt) from [] (drm_atomic_helper_wait_for_vblanks+0xe0/0x1f4 [drm_kms_helper])
[ 99.923445] [] (drm_atomic_helper_wait_for_vblanks [drm_kms_helper]) from [] (vc4_atomic_complete_commit+0x7c/0xbc [vc4])
[ 99.923588] [] (vc4_atomic_complete_commit [vc4]) from [] (vc4_atomic_commit+0x180/0x190 [vc4])
[ 99.923778] [] (vc4_atomic_commit [vc4]) from [] (drm_fb_helper_pan_display+0xa8/0x1d8 [drm_kms_helper])
[ 99.923911] [] (drm_fb_helper_pan_display [drm_kms_helper]) from [] (fb_pan_display+0xf4/0x130)
[ 99.923933] [] (fb_pan_display) from [] (bit_update_start+0x1c/0x38)
[ 99.923951] [] (bit_update_start) from [] (fbcon_switch+0x3b4/0x46c)
[ 99.923969] [] (fbcon_switch) from [] (redraw_screen+0x104/0x1d8)
[ 99.923985] [] (redraw_screen) from [] (fbcon_do_set_font+0x1e8/0x1f8)
[ 99.924003] [] (fbcon_do_set_font) from [] (fbcon_set_font+0x1e8/0x230)
[ 99.924019] [] (fbcon_set_font) from [] (con_font_op+0x1a8/0x4b0)
[ 99.924036] [
Fedora 27 with 4.13.2, mesa 7.2.0 and gnome 3.26, we get a series of crashes in drm_atomic_helper_wait_for_vblanks during the early boot process while X/wayland/gdm is starting up, and sometimes during use, although I'm not testing using thoroughly atm. There seems to be a couple of variations of the crash so I've included them all.