dmesg:
...
nouveau 0000:02:00.0: disp: ERROR 5 [INVALID_STATE] 0b [] chid 1 mthd 0080 data 00000000
nouveau 0000:02:00.0: disp: Base 1:
nouveau 0000:02:00.0: disp: 	0084: 00000000              
nouveau 0000:02:00.0: disp: 	0088: 00000000              
nouveau 0000:02:00.0: disp: 	008c: 00000000              
nouveau 0000:02:00.0: disp: 	0090: 00000000              
nouveau 0000:02:00.0: disp: 	0094: 00000000 -> f0000000
nouveau 0000:02:00.0: disp: 	00a0: 00000000              
nouveau 0000:02:00.0: disp: 	00a4: 00000000              
nouveau 0000:02:00.0: disp: 	00c0: 00000000 -> ffff0000
nouveau 0000:02:00.0: disp: 	00c4: 00000000              
nouveau 0000:02:00.0: disp: 	00c8: 00000000              
nouveau 0000:02:00.0: disp: 	00cc: 00000000              
nouveau 0000:02:00.0: disp: 	00e0: 40000000              
nouveau 0000:02:00.0: disp: 	00e4: 00000000              
nouveau 0000:02:00.0: disp: 	00e8: 00000000              
nouveau 0000:02:00.0: disp: 	00ec: 00000000              
nouveau 0000:02:00.0: disp: 	00fc: 00000000              
nouveau 0000:02:00.0: disp: 	0100: fffe0000              
nouveau 0000:02:00.0: disp: 	0104: 00000000              
nouveau 0000:02:00.0: disp: 	0110: 00000000              
nouveau 0000:02:00.0: disp: 	0114: 00000000              
nouveau 0000:02:00.0: disp: Base 1 - Image 0:
nouveau 0000:02:00.0: disp: 	0800: 00002100 -> 00000500
nouveau 0000:02:00.0: disp: 	0804: 00000000              
nouveau 0000:02:00.0: disp: 	0808: 04380780 -> 03000400
nouveau 0000:02:00.0: disp: 	080c: 00007804 -> 00100800
nouveau 0000:02:00.0: disp: 	0810: 0000cf00 -> 0000e800
nouveau 0000:02:00.0: disp: Base 1 - Image 1:
nouveau 0000:02:00.0: disp: 	0c00: 00002100 -> 00000500
nouveau 0000:02:00.0: disp: 	0c04: 00000000              
nouveau 0000:02:00.0: disp: 	0c08: 04380780 -> 03000400
nouveau 0000:02:00.0: disp: 	0c0c: 00007804 -> 00100800
nouveau 0000:02:00.0: disp: 	0c10: 0000cf00 -> 0000e800
nouveau 0000:02:00.0: DRM: GPU lockup - switching to software fbcon

~~~~~~~~~~~

Xorg.0.log:

X.Org X Server 1.18.3
Release Date: 2016-04-04
X Protocol Version 11, Revision 0
Build Operating System: lnx 4.6.0-456.fc22.x86_64 
...
(EE) [mi] EQ overflowing.  Additional events will be discarded until existing events are processed.
(EE) 
(EE) Backtrace:
(EE) 0: /usr/libexec/Xorg (mieqEnqueue+0x253) [0x575063]
(EE) 1: /usr/libexec/Xorg (QueueKeyboardEvents+0x52) [0x44edb2]
(EE) 2: /usr/libexec/Xorg (xf86PostKeyboardEvent+0x3b) [0x486d9b]
(EE) 3: /usr/lib64/xorg/modules/input/evdev_drv.so (_init+0x32af) [0x7f1b940fa0ff]
(EE) 4: /usr/lib64/xorg/modules/input/evdev_drv.so (_init+0x39bd) [0x7f1b940fb3dd]
(EE) 5: /usr/libexec/Xorg (DPMSSupported+0xe8) [0x477008]
(EE) 6: /usr/libexec/Xorg (xf86SerialModemClearBits+0x2b2) [0x49c2a2]
(EE) 7: /lib64/libpthread.so.0 (__restore_rt+0x0) [0x7f1b9d67842f]
(EE) 8: /lib64/libc.so.6 (ioctl+0x5) [0x7f1b9d39fc85]
(EE) 9: /lib64/libdrm.so.2 (drmIoctl+0x28) [0x7f1b9f5e6508]
(EE) 10: /lib64/libdrm.so.2 (drmCommandWrite+0x1b) [0x7f1b9f5e908b]
(EE) 11: /lib64/libdrm_nouveau.so.2 (nouveau_bo_wait+0xbc) [0x7f1b98b8d38c]
(EE) 12: /usr/lib64/xorg/modules/drivers/nouveau_drv.so (_init+0x219a2) [0x7f1b98dda612]
(EE) 13: /usr/libexec/Xorg (xf86DetachAllCrtc+0xb5b) [0x4b056b]
(EE) 14: /usr/libexec/Xorg (xf86DestroyCursorInfoRec+0xbea) [0x4baf3a]
(EE) 15: /usr/libexec/Xorg (RamDacHandleColormaps+0x899) [0x4b96d9]
(EE) 16: /usr/libexec/Xorg (miPointerUpdateSprite+0x26b) [0x57e62b]
(EE) 17: /usr/libexec/Xorg (miPointerUpdateSprite+0x4ba) [0x57ecca]
(EE) 18: /usr/libexec/Xorg (CompositeRegisterImplicitRedirectionException+0x4329) [0x4cb6c9]
(EE) 19: /usr/libexec/Xorg (AddTraps+0x6ebf) [0x51a93f]
(EE) 20: /usr/libexec/Xorg (ConfineToShape+0x958) [0x440148]
(EE) 21: /usr/libexec/Xorg (WindowHasNewCursor+0x37) [0x440c97]
(EE) 22: /usr/libexec/Xorg (CompositeRegisterImplicitRedirectionException+0x3f94) [0x4cb0b4]
(EE) 23: /usr/libexec/Xorg (CompositeRegisterImplicitRedirectionException+0x4ea6) [0x4cced6]
(EE) 24: /usr/libexec/Xorg (SendErrorToClient+0x2df) [0x436adf]
(EE) 25: /usr/libexec/Xorg (remove_fs_handlers+0x453) [0x43aaf3]
(EE) 26: /lib64/libc.so.6 (__libc_start_main+0xf0) [0x7f1b9d2c7700]
(EE) 27: /usr/libexec/Xorg (_start+0x29) [0x424e39]
(EE) 28: ? (?+0x29) [0x29]
(EE) 
(EE) [mi] These backtraces from mieqEnqueue may point to a culprit higher up the stack.
(EE) [mi] mieq is *NOT* the cause.  It is a victim.