Comment 24 for bug 1567417

Same here on Dell E7470 (SKU:06DC),i5-6300U (Skylake) & 1366x768 model
(non-standards I think not being related just to mention: UEFI+grub, SecureBoot, DualBoot, LL kernel, LVM & LUKS FDE & custom keyscript)

Display quirks from time to time and I see lines below in dmesg.

Not related to screen locking, happens less then 4 seconds after clean boot and then randomly.
Nothing nvidia related installed on system.
Seen complaints about missing firmware while updating initramfs...
W: Possible missing firmware /lib/firmware/i915/kbl_dmc_ver1.bin for module i915_bpo
Don't know whether it could be related?
CPU/GPU is skl not kbl however - so probably not.

[58737.425265] ------------[ cut here ]------------
[58737.425280] WARNING: CPU: 0 PID: 1289 at /build/linux-W6HB68/linux-4.4.0/ubuntu/i915/intel_pm.c:3675 skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]()
[58737.425281] WARN_ON(!wm_changed)
[58737.425282] Modules linked in:
[58737.425283] uas usb_storage rfcomm bnep nls_iso8859_1 snd_soc_skl snd_soc_skl_ipc snd_hda_ext_core snd_soc_sst_ipc snd_soc_sst_dsp snd_hda_codec_hdmi dell_wmi sparse_keymap snd_soc_core dell_led snd_compress ac97_bus snd_hda_codec_realtek snd_hda_codec_generic dell_laptop dcdbas snd_pcm_dmaengine arc4 dw_dmac_core snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep snd_pcm snd_seq_midi dell_smm_hwmon snd_seq_midi_event snd_rawmidi iwlmvm intel_rapl x86_pkg_temp_thermal mac80211 intel_powerclamp coretemp kvm_intel kvm snd_seq snd_seq_device snd_timer irqbypass iwlwifi joydev snd uvcvideo serio_raw videobuf2_vmalloc hci_uart cfg80211 videobuf2_memops videobuf2_v4l2 btqca videobuf2_core v4l2_common rtsx_pci_ms btusb videodev memstick btrtl soundcore input_leds btbcm btintel bluetooth media mei_me shpchp
[58737.425307] mei 8250_fintek int3403_thermal intel_lpss_acpi intel_lpss processor_thermal_device mac_hid dell_rbtn int340x_thermal_zone intel_soc_dts_iosf acpi_pad int3400_thermal acpi_thermal_rel acpi_als kfifo_buf industrialio parport_pc ppdev lp parport autofs4 drbg ansi_cprng algif_skcipher af_alg dm_crypt hid_generic usbhid rtsx_pci_sdmmc i915_bpo crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 intel_ips lrw i2c_algo_bit gf128mul glue_helper ablk_helper e1000e drm_kms_helper cryptd syscopyarea sysfillrect ptp sysimgblt fb_sys_fops psmouse pps_core drm rtsx_pci ahci libahci wmi i2c_hid pinctrl_sunrisepoint video pinctrl_intel hid fjes
[58737.425328] CPU: 0 PID: 1289 Comm: Xorg Tainted: G W 4.4.0-62-lowlatency #83-Ubuntu
[58737.425329] Hardware name: Dell Inc. Latitude E7470/0T6HHJ, BIOS 1.9.4 08/26/2016
[58737.425330] 0000000000000286 0000000000a63bca ffff88009742f920 ffffffff81400f01
[58737.425332] ffff88009742f968 ffffffffc02fe9a8 ffff88009742f958 ffffffff81081d02
[58737.425333] ffff8804342c9000 ffff880433d8a148 ffff8804342ca000 ffff88043b3de378
[58737.425335] Call Trace:
[58737.425338] [<ffffffff81400f01>] dump_stack+0x63/0x82
[58737.425340] [<ffffffff81081d02>] warn_slowpath_common+0x82/0xc0
[58737.425342] [<ffffffff81081d9c>] warn_slowpath_fmt+0x5c/0x80
[58737.425354] [<ffffffffc022005c>] skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]
[58737.425365] [<ffffffffc02201f5>] skl_update_wm+0x185/0x610 [i915_bpo]
[58737.425383] [<ffffffffc02b1dff>] ? intel_ddi_enable_transcoder_func+0x17f/0x260 [i915_bpo]
[58737.425394] [<ffffffffc0223e3e>] intel_update_watermarks+0x1e/0x30 [i915_bpo]
[58737.425411] [<ffffffffc02940d1>] haswell_crtc_enable+0x761/0x8e0 [i915_bpo]
[58737.425427] [<ffffffffc028ffe1>] intel_atomic_commit+0x5d1/0x1490 [i915_bpo]
[58737.425440] [<ffffffffc00b7c6e>] ? drm_atomic_check_only+0x18e/0x590 [drm]
[58737.425450] [<ffffffffc00b80a7>] drm_atomic_commit+0x37/0x60 [drm]
[58737.425456] [<ffffffffc0153dc6>] drm_atomic_helper_set_config+0x76/0xb0 [drm_kms_helper]
[58737.425466] [<ffffffffc00a6ec2>] drm_mode_set_config_internal+0x62/0x100 [drm]
[58737.425476] [<ffffffffc00ab51c>] drm_mode_setcrtc+0x3cc/0x4f0 [drm]
[58737.425483] [<ffffffffc009c782>] drm_ioctl+0x152/0x540 [drm]
[58737.425491] [<ffffffffc00ab150>] ? drm_mode_setplane+0x1b0/0x1b0 [drm]
[58737.425493] [<ffffffff8122782f>] do_vfs_ioctl+0x29f/0x490
[58737.425495] [<ffffffff8103c74d>] ? fpu__restore_sig+0x4d/0x60
[58737.425497] [<ffffffff81227a99>] SyS_ioctl+0x79/0x90
[58737.425499] [<ffffffff81845c32>] entry_SYSCALL_64_fastpath+0x16/0x71
[58737.425518] ---[ end trace 17785936ce5f0c92 ]---
[63106.113600] [drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe B FIFO underrun
[63589.182957] [drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe C FIFO underrun
[63644.203994] [drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe A FIFO underrun