Tested on SKLY03 with the testing kernel drm-intel-testing-2015-05-08.
this problem still exists.
Output:
[ 7306.872817] ------------[ cut here ]------------
[ 7306.872852] WARNING: CPU: 2 PID: 1004 at drivers/gpu/drm/i915/intel_pm.c:3346 skl_update_other_pipe_wm+0x10b/0x148 [i915]()
[ 7306.872855] WARN_ON(!wm_changed)
[ 7306.872874] Modules linked in: dm_mod snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep snd_pcm ppdev serio_raw pcspkr snd_timer i2c_i801 snd soundcore wmi battery parport_pc parport ac acpi_cpufreq i915 button video drm_kms_helper drm
[ 7306.872880] CPU: 2 PID: 1004 Comm: kworker/2:1 Tainted: G     U  W       4.1.0-rc2_drm-intel-testing-2015-05-08+ #2
[ 7306.872882] Hardware name: Intel Corporation Skylake Client platform/Skylake Y LPDDR3 RVP3, BIOS SKLSE2R1.R00.B082.B00.1504240146 04/24/2015
[ 7306.872891] Workqueue: events console_callback
[ 7306.872896]  0000000000000000 0000000000000009 ffffffff817a66cc ffff88016864f748
[ 7306.872899]  ffffffff8103ebde ffff88016864f91a ffffffffa0083030 ffff88007bb10000
[ 7306.872902]  ffff88016864f86c ffff880163628000 ffff880163b7c000 ffff88007bb1955c
[ 7306.872903] Call Trace:
[ 7306.872913]  [<ffffffff817a66cc>] ? dump_stack+0x40/0x50
[ 7306.872918]  [<ffffffff8103ebde>] ? warn_slowpath_common+0x98/0xb0
[ 7306.872941]  [<ffffffffa0083030>] ? skl_update_other_pipe_wm+0x10b/0x148 [i915]
[ 7306.872944]  [<ffffffff8103ec3b>] ? warn_slowpath_fmt+0x45/0x4a
[ 7306.872968]  [<ffffffffa0083030>] ? skl_update_other_pipe_wm+0x10b/0x148 [i915]
[ 7306.872992]  [<ffffffffa00831a2>] ? skl_update_wm+0x135/0x5c5 [i915]
[ 7306.872996]  [<ffffffff81073917>] ? log_store+0x14f/0x196
[ 7306.873000]  [<ffffffff8106a278>] ? down_trylock+0x20/0x29
[ 7306.873003]  [<ffffffff810736ec>] ? console_trylock+0x10/0x55
[ 7306.873044]  [<ffffffffa00d3485>] ? haswell_crtc_disable+0x271/0x2bc [i915]
[ 7306.873079]  [<ffffffffa00d4fa1>] ? intel_crtc_control+0x97/0xd2 [i915]
[ 7306.873111]  [<ffffffffa00d5020>] ? intel_crtc_update_dpms+0x44/0x52 [i915]
[ 7306.873144]  [<ffffffffa00d99b5>] ? intel_connector_dpms+0x3f/0x4a [i915]
[ 7306.873153]  [<ffffffffa0059d28>] ? drm_fb_helper_dpms.isra.5+0x8b/0xcc [drm_kms_helper]
[ 7306.873160]  [<ffffffffa0059d9b>] ? drm_fb_helper_blank+0x32/0x39 [drm_kms_helper]
[ 7306.873191]  [<ffffffffa00e6593>] ? intel_fbdev_blank+0x11/0x54 [i915]
[ 7306.873198]  [<ffffffff813862bc>] ? fb_blank+0x53/0x86
[ 7306.873203]  [<ffffffff8137f22e>] ? fbcon_blank+0x172/0x228
[ 7306.873208]  [<ffffffff81381ebc>] ? bit_cursor+0x459/0x486
[ 7306.873214]  [<ffffffff8108016c>] ? lock_timer_base.isra.37+0x22/0x46
[ 7306.873220]  [<ffffffff81080ace>] ? try_to_del_timer_sync+0x46/0x51
[ 7306.873224]  [<ffffffff813d46f3>] ? do_blank_screen+0x187/0x251
[ 7306.873260]  [<ffffffff813d6a1e>] ? console_callback+0xc6/0xed
[ 7306.873264]  [<ffffffff8104f985>] ? process_one_work+0x1b2/0x31d
[ 7306.873268]  [<ffffffff8105026f>] ? worker_thread+0x265/0x351
[ 7306.873272]  [<ffffffff8105000a>] ? cancel_delayed_work_sync+0xa/0xa
[ 7306.873276]  [<ffffffff81053ee1>] ? kthread+0xce/0xd6
[ 7306.873281]  [<ffffffff81053e13>] ? kthread_create_on_node+0x162/0x162
[ 7306.873285]  [<ffffffff817ac5d2>] ? ret_from_fork+0x42/0x70
[ 7306.873290]  [<ffffffff81053e13>] ? kthread_create_on_node+0x162/0x162
[ 7306.873293] ---[ end trace 8103221c8aae6cbc ]---