On a HSW-GT2:

IGT-Version: 1.13-g925e5e1 (x86_64) (Linux: 4.5.0-rc6-gfxbench+ x86_64)
[...]
Beginning basic-flip-vs-wf_vblank on pipe C, connector HDMI-A-1
  1920x1080 60 1920 2008 2052 2200 1080 1084 1089 1125 0x5 0x48 148500
Stack trace:
  #0 [__igt_fail_assert+0x101]
  #1 [check_state+0x32b]
  #2 [<unknown>+0x32b]
Subtest basic-flip-vs-wf_vblank: FAIL (35.873s)
[...]
(kms_flip:6460) INFO: Beginning basic-flip-vs-wf_vblank on pipe C, connector HDMI-A-1
(kms_flip:6460) igt-fb-DEBUG: igt_create_fb_with_bo_size(width=1920, height=1080, format=0x34325258 [bpp=32], tiling=0x0, size=0)
(kms_flip:6460) igt-fb-DEBUG: igt_create_fb_with_bo_size(handle=2, pitch=7680)
(kms_flip:6460) igt-fb-DEBUG: igt_create_fb_with_bo_size(width=1920, height=1080, format=0x34325258 [bpp=32], tiling=0x0, size=0)
(kms_flip:6460) igt-fb-DEBUG: igt_create_fb_with_bo_size(handle=3, pitch=7680)
(kms_flip:6460) igt-fb-DEBUG: igt_create_fb_with_bo_size(width=1920, height=1080, format=0x34325258 [bpp=32], tiling=0x100000000000001, size=0)
(kms_flip:6460) igt-fb-DEBUG: igt_create_fb_with_bo_size(handle=4, pitch=7680)
(kms_flip:6460) igt-kms-INFO:   1920x1080 60 1920 2008 2052 2200 1080 1084 1089 1125 0x5 0x48 148500
[...]
(kms_flip:6460) DEBUG: name = flip
last_ts = 340.777124 usec
last_received_ts = 340.776742 usec
last_seq = 635
current_ts = 340.943796 usec
current_received_ts = 340.943400 usec
current_seq = 645
count = 20
seq_step = 1
(kms_flip:6460) DEBUG: name = vblank
last_ts = 340.927124 usec
last_received_ts = 340.926727 usec
last_seq = 644
current_ts = 341.110458 usec
current_received_ts = 341.110125 usec
current_seq = 654
count = 20
seq_step = 10
(kms_flip:6460) CRITICAL: Test assertion failure function check_state, file kms_flip.c:692:
(kms_flip:6460) CRITICAL: Failed assertion: fabs((((double) diff.tv_usec) - usec_interflip) / usec_interflip) <= 0.005
(kms_flip:6460) CRITICAL: Last errno: 25, Inappropriate ioctl for device
(kms_flip:6460) CRITICAL: inter-vblank ts jitter: 0s, 183334usec
****  END  ****