Comment 3 for bug 1574648

Here's (I think) the relevant section of the Kernel Log:

May 3 09:07:57 andor-Lemur kernel: [ 2.829933] ------------[ cut here ]------------
May 3 09:07:57 andor-Lemur kernel: [ 2.829952] WARNING: CPU: 3 PID: 24 at /build/linux-yplzxd/linux-4.4.0/ubuntu/i915/intel_pm.c:3572 skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]()
May 3 09:07:57 andor-Lemur kernel: [ 2.829954] WARN_ON(!wm_changed)
May 3 09:07:57 andor-Lemur kernel: [ 2.829954] Modules linked in: autofs4 mmc_block rtsx_pci_sdmmc i915_bpo intel_ips i2c_algo_bit drm_kms_helper syscopyarea sysfillrect psmouse sysimgblt fb_sys_fops drm r8169 ahci rtsx_pci mii libahci wmi video pinctrl_sunrisepoint i2c_hid pinctrl_intel hid fjes
May 3 09:07:57 andor-Lemur kernel: [ 2.829981] CPU: 3 PID: 24 Comm: kworker/3:0 Not tainted 4.4.0-22-generic #38-Ubuntu
May 3 09:07:57 andor-Lemur kernel: [ 2.829982] Hardware name: System76, Inc. Lemur /Lemur , BIOS 1.05.06RS76 11/29/2015
May 3 09:07:57 andor-Lemur kernel: [ 2.829987] Workqueue: events output_poll_execute [drm_kms_helper]
May 3 09:07:57 andor-Lemur kernel: [ 2.829988] 0000000000000286 00000000ab9642dc ffff880460d73950 ffffffff813e9c73
May 3 09:07:57 andor-Lemur kernel: [ 2.829990] ffff880460d73998 ffffffffc028ac70 ffff880460d73988 ffffffff81080fb2
May 3 09:07:57 andor-Lemur kernel: [ 2.829991] ffff880460ed6000 ffff88045aa99d9c ffff880460ed5000 ffff88045ae7fb78
May 3 09:07:57 andor-Lemur kernel: [ 2.829992] Call Trace:
May 3 09:07:57 andor-Lemur kernel: [ 2.829996] [<ffffffff813e9c73>] dump_stack+0x63/0x90
May 3 09:07:57 andor-Lemur kernel: [ 2.829999] [<ffffffff81080fb2>] warn_slowpath_common+0x82/0xc0
May 3 09:07:57 andor-Lemur kernel: [ 2.830000] [<ffffffff8108104c>] warn_slowpath_fmt+0x5c/0x80
May 3 09:07:57 andor-Lemur kernel: [ 2.830010] [<ffffffffc01bc5cc>] skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]
May 3 09:07:57 andor-Lemur kernel: [ 2.830019] [<ffffffffc01bc766>] skl_update_wm+0x186/0x5f0 [i915_bpo]
May 3 09:07:57 andor-Lemur kernel: [ 2.830033] [<ffffffffc024836f>] ? intel_ddi_enable_transcoder_func+0x17f/0x260 [i915_bpo]
May 3 09:07:57 andor-Lemur kernel: [ 2.830046] [<ffffffffc01c048e>] intel_update_watermarks+0x1e/0x30 [i915_bpo]
May 3 09:07:57 andor-Lemur kernel: [ 2.830065] [<ffffffffc022c401>] haswell_crtc_enable+0x321/0x8c0 [i915_bpo]
May 3 09:07:57 andor-Lemur kernel: [ 2.830084] [<ffffffffc0218a8e>] ? intel_finish_crtc_commit+0xe/0x10 [i915_bpo]
May 3 09:07:57 andor-Lemur kernel: [ 2.830090] [<ffffffffc0172314>] ? drm_atomic_helper_commit_planes_on_crtc+0x154/0x270 [drm_kms_helper]
May 3 09:07:57 andor-Lemur kernel: [ 2.830109] [<ffffffffc0228dad>] intel_atomic_commit+0x5dd/0xdb0 [i915_bpo]
May 3 09:07:57 andor-Lemur kernel: [ 2.830126] [<ffffffffc00cd80e>] ? drm_atomic_check_only+0x18e/0x590 [drm]
May 3 09:07:57 andor-Lemur kernel: [ 2.830138] [<ffffffffc00cdc47>] drm_atomic_commit+0x37/0x60 [drm]
May 3 09:07:57 andor-Lemur kernel: [ 2.830144] [<ffffffffc01735df>] restore_fbdev_mode+0x22f/0x260 [drm_kms_helper]
May 3 09:07:57 andor-Lemur kernel: [ 2.830156] [<ffffffffc00cc46a>] ? drm_modeset_lock_all_ctx+0x9a/0xb0 [drm]
May 3 09:07:57 andor-Lemur kernel: [ 2.830161] [<ffffffffc01757c3>] drm_fb_helper_restore_fbdev_mode_unlocked+0x33/0x80 [drm_kms_helper]
May 3 09:07:57 andor-Lemur kernel: [ 2.830164] [<ffffffffc017583d>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
May 3 09:07:57 andor-Lemur kernel: [ 2.830167] [<ffffffffc0175742>] drm_fb_helper_hotplug_event+0xd2/0x120 [drm_kms_helper]
May 3 09:07:57 andor-Lemur kernel: [ 2.830181] [<ffffffffc023f65e>] intel_fbdev_output_poll_changed+0x1e/0x30 [i915_bpo]
May 3 09:07:57 andor-Lemur kernel: [ 2.830184] [<ffffffffc01686e7>] drm_kms_helper_hotplug_event+0x27/0x30 [drm_kms_helper]
May 3 09:07:57 andor-Lemur kernel: [ 2.830187] [<ffffffffc01688e7>] output_poll_execute+0x197/0x1e0 [drm_kms_helper]
May 3 09:07:57 andor-Lemur kernel: [ 2.830189] [<ffffffff8109a052>] process_one_work+0x162/0x480
May 3 09:07:57 andor-Lemur kernel: [ 2.830191] [<ffffffff8109a3bb>] worker_thread+0x4b/0x4c0
May 3 09:07:57 andor-Lemur kernel: [ 2.830193] [<ffffffff8109a370>] ? process_one_work+0x480/0x480
May 3 09:07:57 andor-Lemur kernel: [ 2.830194] [<ffffffff810a0588>] kthread+0xd8/0xf0
May 3 09:07:57 andor-Lemur kernel: [ 2.830196] [<ffffffff810a04b0>] ? kthread_create_on_node+0x1e0/0x1e0
May 3 09:07:57 andor-Lemur kernel: [ 2.830198] [<ffffffff8182568f>] ret_from_fork+0x3f/0x70
May 3 09:07:57 andor-Lemur kernel: [ 2.830200] [<ffffffff810a04b0>] ? kthread_create_on_node+0x1e0/0x1e0
May 3 09:07:57 andor-Lemur kernel: [ 2.830201] ---[ end trace 9fdb41f1dc06c78f ]---