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[Bug 1567417] Re: WARN_ON(!wm_changed) skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]

 

apport information

** Tags added: apport-collected xenial

** Description changed:

  Hi,
  
  I'm using a new Skylake Thinkpad T460s with and external monitor
  connected via Displayport and Ubuntu 16.04 and the latest kernel as of
  today: Linux test 4.4.0-17-generic #33-Ubuntu SMP Tue Mar 29 17:17:28
  UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
  
  X will from time to time lock up when the computer is left idle for a
  long time and both displays (laptop and external) go to sleep and then
  woken up.
  
  Apr  7 08:00:49 test kernel: [    9.950929] ------------[ cut here ]------------
  Apr  7 08:00:49 test kernel: [    9.950950] WARNING: CPU: 0 PID: 214 at /build/linux-YiIlnA/linux-4.4.0/ubuntu/i915/intel_pm.c:3572 skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]()
  Apr  7 08:00:49 test kernel: [    9.950951] WARN_ON(!wm_changed)
  Apr  7 08:00:49 test kernel: [    9.950972] Modules linked in: btusb btrtl btbcm btintel bluetooth binfmt_misc nls_iso8859_1 arc4 snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic snd_soc_skl snd_soc_skl_ipc snd_hda_ext_core snd_soc_sst_ipc snd_soc_sst_dsp snd_soc_core snd_compress ac97_bus snd_pcm_dmaengine dw_dmac_core snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep snd_pcm thinkpad_acpi intel_rapl x86_pkg_temp_thermal nvram intel_powerclamp snd_seq_midi coretemp snd_seq_midi_event snd_rawmidi iwlmvm snd_seq joydev snd_seq_device input_leds mac80211 snd_timer serio_raw snd rtsx_pci_ms memstick soundcore iwlwifi cfg80211 mei_me mei tpm_crb mac_hid shpchp kvm_intel kvm irqbypass parport_pc ppdev lp parport autofs4 drbg ansi_cprng algif_skcipher af_alg hid_microsoft dm_crypt hid_generic usbhid hid rtsx_pci_sdmmc crct10dif_pclmul crc32_pclmul i915_bpo aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd intel_ips i2c_algo_bit drm_kms_helper e1000e syscopyarea sysfillrect psmouse sysimgblt ptp fb_sys_fops pps_core drm nvme rtsx_pci wmi video fjes
  Apr  7 08:00:49 test kernel: [    9.950980] CPU: 0 PID: 214 Comm: plymouthd Not tainted 4.4.0-17-generic #33-Ubuntu
  Apr  7 08:00:49 test kernel: [    9.950981] Hardware name: LENOVO 20F9CTO1WW/20F9CTO1WW, BIOS N1CET40W (1.08 ) 03/09/2016
  Apr  7 08:00:49 test kernel: [    9.950982]  0000000000000286 0000000039cb6999 ffff880502bc3618 ffffffff813e8123
  Apr  7 08:00:49 test kernel: [    9.950983]  ffff880502bc3660 ffffffffc0343c70 ffff880502bc3650 ffffffff8107fe12
  Apr  7 08:00:49 test kernel: [    9.950984]  ffff880502da8000 ffff880501f79d9c ffff880502dab000 ffff880508186b78
  Apr  7 08:00:49 test kernel: [    9.950984] Call Trace:
  Apr  7 08:00:49 test kernel: [    9.950988]  [<ffffffff813e8123>] dump_stack+0x63/0x90
  Apr  7 08:00:49 test kernel: [    9.950990]  [<ffffffff8107fe12>] warn_slowpath_common+0x82/0xc0
  Apr  7 08:00:49 test kernel: [    9.950991]  [<ffffffff8107feac>] warn_slowpath_fmt+0x5c/0x80
  Apr  7 08:00:49 test kernel: [    9.951002]  [<ffffffffc02755cc>] skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951010]  [<ffffffffc0275766>] skl_update_wm+0x186/0x5f0 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951023]  [<ffffffffc03013af>] ? intel_ddi_enable_transcoder_func+0x17f/0x260 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951034]  [<ffffffffc027948e>] intel_update_watermarks+0x1e/0x30 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951048]  [<ffffffffc02e5441>] haswell_crtc_enable+0x321/0x8c0 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951061]  [<ffffffffc02d1ace>] ? intel_finish_crtc_commit+0xe/0x10 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951072]  [<ffffffffc017b324>] ? drm_atomic_helper_commit_planes_on_crtc+0x154/0x270 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951085]  [<ffffffffc02e1ded>] intel_atomic_commit+0x5dd/0xdb0 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951101]  [<ffffffffc007180e>] ? drm_atomic_check_only+0x18e/0x590 [drm]
  Apr  7 08:00:49 test kernel: [    9.951109]  [<ffffffffc0071c47>] drm_atomic_commit+0x37/0x60 [drm]
  Apr  7 08:00:49 test kernel: [    9.951113]  [<ffffffffc017c5ef>] restore_fbdev_mode+0x22f/0x260 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951121]  [<ffffffffc007046a>] ? drm_modeset_lock_all_ctx+0x9a/0xb0 [drm]
  Apr  7 08:00:49 test kernel: [    9.951125]  [<ffffffffc017e7d3>] drm_fb_helper_restore_fbdev_mode_unlocked+0x33/0x80 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951128]  [<ffffffffc017e84d>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951131]  [<ffffffffc017e752>] drm_fb_helper_hotplug_event+0xd2/0x120 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951134]  [<ffffffffc017e7f6>] drm_fb_helper_restore_fbdev_mode_unlocked+0x56/0x80 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951136]  [<ffffffffc017e84d>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951150]  [<ffffffffc02f79aa>] intel_fbdev_set_par+0x1a/0x60 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951151]  [<ffffffff8146b2b6>] fb_set_var+0x236/0x460
  Apr  7 08:00:49 test kernel: [    9.951153]  [<ffffffff810b217d>] ? select_idle_sibling+0xbd/0x120
  Apr  7 08:00:49 test kernel: [    9.951155]  [<ffffffff810b3441>] ? wakeup_preempt_entity.isra.55+0x41/0x50
  Apr  7 08:00:49 test kernel: [    9.951156]  [<ffffffff810b3e8a>] ? check_preempt_wakeup+0xfa/0x220
  Apr  7 08:00:49 test kernel: [    9.951158]  [<ffffffff814615af>] fbcon_blank+0x30f/0x350
  Apr  7 08:00:49 test kernel: [    9.951160]  [<ffffffff814f85c3>] do_unblank_screen+0xd3/0x1a0
  Apr  7 08:00:49 test kernel: [    9.951161]  [<ffffffff814edc4a>] vt_ioctl+0x50a/0x12f0
  Apr  7 08:00:49 test kernel: [    9.951167]  [<ffffffffc0056749>] ? drm_ioctl+0x189/0x540 [drm]
  Apr  7 08:00:49 test kernel: [    9.951168]  [<ffffffff814e117f>] tty_ioctl+0x35f/0xc40
  Apr  7 08:00:49 test kernel: [    9.951170]  [<ffffffff81821f79>] ? schedule_hrtimeout_range_clock+0xb9/0x1b0
  Apr  7 08:00:49 test kernel: [    9.951172]  [<ffffffff812544eb>] ? ep_poll+0x37b/0x3d0
  Apr  7 08:00:49 test kernel: [    9.951173]  [<ffffffff8121ef3f>] do_vfs_ioctl+0x29f/0x490
  Apr  7 08:00:49 test kernel: [    9.951175]  [<ffffffff810aaca0>] ? wake_up_q+0x70/0x70
  Apr  7 08:00:49 test kernel: [    9.951176]  [<ffffffff8121f1a9>] SyS_ioctl+0x79/0x90
  Apr  7 08:00:49 test kernel: [    9.951177]  [<ffffffff81822b72>] entry_SYSCALL_64_fastpath+0x16/0x71
  Apr  7 08:00:49 test kernel: [    9.951178] ---[ end trace 7e448a85359a7dca ]---
  
  
  Attached is the full kernel log from boot until the issue happens, at which point, if I have a lockup of X I need to reboot to get back to normal.
  
  I don't know if this particular bug I'm reporting is the one responsible
  for the lockups, as I've isolated 4 different warning/error messages
  which separately or in combination may be the cause.   I'm reporting all
  of them now in separate bug reports.
  
  Please let me know if any information is missing.
  
  # lspci
  00:00.0 Host bridge: Intel Corporation Sky Lake Host Bridge/DRAM Registers (rev 08)
  00:02.0 VGA compatible controller: Intel Corporation Sky Lake Integrated Graphics (rev 07)
  00:08.0 System peripheral: Intel Corporation Sky Lake Gaussian Mixture Model
  00:14.0 USB controller: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller (rev 21)
  00:14.2 Signal processing controller: Intel Corporation Sunrise Point-LP Thermal subsystem (rev 21)
  00:16.0 Communication controller: Intel Corporation Sunrise Point-LP CSME HECI (rev 21)
  00:1c.0 PCI bridge: Intel Corporation Device 9d10 (rev f1)
  00:1c.2 PCI bridge: Intel Corporation Device 9d12 (rev f1)
  00:1c.4 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port (rev f1)
  00:1f.0 ISA bridge: Intel Corporation Sunrise Point-LP LPC Controller (rev 21)
  00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
  00:1f.3 Audio device: Intel Corporation Sunrise Point-LP HD Audio (rev 21)
  00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
  00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection I219-LM (rev 21)
  02:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS522A PCI Express Card Reader (rev 01)
  04:00.0 Network controller: Intel Corporation Wireless 8260 (rev 3a)
  05:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller (rev 01)
  
  # lspci -vvv
  00:00.0 Host bridge: Intel Corporation Sky Lake Host Bridge/DRAM Registers (rev 08)
          Subsystem: Lenovo Skylake Host Bridge/DRAM Registers
          Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
          Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort+ >SERR- <PERR- INTx-
          Latency: 0
          Capabilities: [e0] Vendor Specific Information: Len=10 <?>
  
  00:02.0 VGA compatible controller: Intel Corporation Sky Lake Integrated Graphics (rev 07) (prog-if 00 [VGA controller])
          Subsystem: Lenovo Skylake Integrated Graphics
          Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
          Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
          Latency: 0
          Interrupt: pin A routed to IRQ 133
          Region 0: Memory at f0000000 (64-bit, non-prefetchable) [size=16M]
          Region 2: Memory at e0000000 (64-bit, prefetchable) [size=256M]
          Region 4: I/O ports at e000 [size=64]
          Expansion ROM at <unassigned> [disabled]
          Capabilities: [40] Vendor Specific Information: Len=0c <?>
          Capabilities: [70] Express (v2) Root Complex Integrated Endpoint, MSI 00
                  DevCap: MaxPayload 128 bytes, PhantFunc 0
                          ExtTag- RBE+
                  DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
                          RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
                          MaxPayload 128 bytes, MaxReadReq 128 bytes
                  DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend-
                  DevCap2: Completion Timeout: Not Supported, TimeoutDis-, LTR-, OBFF Not Supported
                  DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-, LTR-, OBFF Disabled
          Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
                  Address: fee00018  Data: 0000
          Capabilities: [d0] Power Management version 2
                  Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
                  Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
          Capabilities: [100 v1] #1b
          Capabilities: [200 v1] Address Translation Service (ATS)
                  ATSCap: Invalidate Queue Depth: 00
                  ATSCtl: Enable-, Smallest Translation Unit: 00
          Capabilities: [300 v1] #13
          Kernel driver in use: i915_bpo
          Kernel modules: i915_bpo
  
  
  # for file in /sys/module/i915_bpo/parameters/*; do echo -en $file"\t"; cat $file; done;
  /sys/module/i915_bpo/parameters/disable_display N
  /sys/module/i915_bpo/parameters/disable_power_well      1
  /sys/module/i915_bpo/parameters/edp_vswing      0
  /sys/module/i915_bpo/parameters/enable_cmd_parser       1
  /sys/module/i915_bpo/parameters/enable_dc       -1
  /sys/module/i915_bpo/parameters/enable_execlists        1
  /sys/module/i915_bpo/parameters/enable_fbc      -1
  /sys/module/i915_bpo/parameters/enable_guc_submission   N
  /sys/module/i915_bpo/parameters/enable_hangcheck        Y
  /sys/module/i915_bpo/parameters/enable_ips      1
  /sys/module/i915_bpo/parameters/enable_ppgtt    3
  /sys/module/i915_bpo/parameters/enable_psr      0
  /sys/module/i915_bpo/parameters/enable_rc6      1
  /sys/module/i915_bpo/parameters/fastboot        N
  /sys/module/i915_bpo/parameters/guc_log_level   -1
  /sys/module/i915_bpo/parameters/invert_brightness       0
  /sys/module/i915_bpo/parameters/load_detect_test        N
  /sys/module/i915_bpo/parameters/lvds_channel_mode       0
  /sys/module/i915_bpo/parameters/lvds_use_ssc    -1
  /sys/module/i915_bpo/parameters/mmio_debug      0
  /sys/module/i915_bpo/parameters/modeset -1
  /sys/module/i915_bpo/parameters/nuclear_pageflip        N
  /sys/module/i915_bpo/parameters/panel_ignore_lid        1
  /sys/module/i915_bpo/parameters/prefault_disable        N
  /sys/module/i915_bpo/parameters/preliminary_hw_support  0
  /sys/module/i915_bpo/parameters/reset   Y
  /sys/module/i915_bpo/parameters/semaphores      -1
  /sys/module/i915_bpo/parameters/use_mmio_flip   0
  /sys/module/i915_bpo/parameters/vbt_sdvo_panel_type     -1
  /sys/module/i915_bpo/parameters/verbose_state_checks    Y
+ --- 
+ ApportVersion: 2.20.1-0ubuntu2.1
+ Architecture: amd64
+ DistroRelease: Ubuntu 16.04
+ InstallationDate: Installed on 2016-04-03 (63 days ago)
+ InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Beta amd64 (20160401)
+ Package: linux (not installed)
+ Tags:  xenial
+ Uname: Linux 4.6.0-040600rc7-generic x86_64
+ UnreportableReason: The running kernel is not an Ubuntu kernel
+ UpgradeStatus: No upgrade log present (probably fresh install)
+ UserGroups:
+  
+ _MarkForUpload: True

** Attachment added: "JournalErrors.txt"
   https://bugs.launchpad.net/bugs/1567417/+attachment/4677896/+files/JournalErrors.txt

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https://bugs.launchpad.net/bugs/1567417

Title:
  WARN_ON(!wm_changed) skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  Hi,

  I'm using a new Skylake Thinkpad T460s with and external monitor
  connected via Displayport and Ubuntu 16.04 and the latest kernel as of
  today: Linux test 4.4.0-17-generic #33-Ubuntu SMP Tue Mar 29 17:17:28
  UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

  X will from time to time lock up when the computer is left idle for a
  long time and both displays (laptop and external) go to sleep and then
  woken up.

  Apr  7 08:00:49 test kernel: [    9.950929] ------------[ cut here ]------------
  Apr  7 08:00:49 test kernel: [    9.950950] WARNING: CPU: 0 PID: 214 at /build/linux-YiIlnA/linux-4.4.0/ubuntu/i915/intel_pm.c:3572 skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]()
  Apr  7 08:00:49 test kernel: [    9.950951] WARN_ON(!wm_changed)
  Apr  7 08:00:49 test kernel: [    9.950972] Modules linked in: btusb btrtl btbcm btintel bluetooth binfmt_misc nls_iso8859_1 arc4 snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic snd_soc_skl snd_soc_skl_ipc snd_hda_ext_core snd_soc_sst_ipc snd_soc_sst_dsp snd_soc_core snd_compress ac97_bus snd_pcm_dmaengine dw_dmac_core snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep snd_pcm thinkpad_acpi intel_rapl x86_pkg_temp_thermal nvram intel_powerclamp snd_seq_midi coretemp snd_seq_midi_event snd_rawmidi iwlmvm snd_seq joydev snd_seq_device input_leds mac80211 snd_timer serio_raw snd rtsx_pci_ms memstick soundcore iwlwifi cfg80211 mei_me mei tpm_crb mac_hid shpchp kvm_intel kvm irqbypass parport_pc ppdev lp parport autofs4 drbg ansi_cprng algif_skcipher af_alg hid_microsoft dm_crypt hid_generic usbhid hid rtsx_pci_sdmmc crct10dif_pclmul crc32_pclmul i915_bpo aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd intel_ips i2c_algo_bit drm_kms_helper e1000e syscopyarea sysfillrect psmouse sysimgblt ptp fb_sys_fops pps_core drm nvme rtsx_pci wmi video fjes
  Apr  7 08:00:49 test kernel: [    9.950980] CPU: 0 PID: 214 Comm: plymouthd Not tainted 4.4.0-17-generic #33-Ubuntu
  Apr  7 08:00:49 test kernel: [    9.950981] Hardware name: LENOVO 20F9CTO1WW/20F9CTO1WW, BIOS N1CET40W (1.08 ) 03/09/2016
  Apr  7 08:00:49 test kernel: [    9.950982]  0000000000000286 0000000039cb6999 ffff880502bc3618 ffffffff813e8123
  Apr  7 08:00:49 test kernel: [    9.950983]  ffff880502bc3660 ffffffffc0343c70 ffff880502bc3650 ffffffff8107fe12
  Apr  7 08:00:49 test kernel: [    9.950984]  ffff880502da8000 ffff880501f79d9c ffff880502dab000 ffff880508186b78
  Apr  7 08:00:49 test kernel: [    9.950984] Call Trace:
  Apr  7 08:00:49 test kernel: [    9.950988]  [<ffffffff813e8123>] dump_stack+0x63/0x90
  Apr  7 08:00:49 test kernel: [    9.950990]  [<ffffffff8107fe12>] warn_slowpath_common+0x82/0xc0
  Apr  7 08:00:49 test kernel: [    9.950991]  [<ffffffff8107feac>] warn_slowpath_fmt+0x5c/0x80
  Apr  7 08:00:49 test kernel: [    9.951002]  [<ffffffffc02755cc>] skl_update_other_pipe_wm+0x16c/0x180 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951010]  [<ffffffffc0275766>] skl_update_wm+0x186/0x5f0 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951023]  [<ffffffffc03013af>] ? intel_ddi_enable_transcoder_func+0x17f/0x260 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951034]  [<ffffffffc027948e>] intel_update_watermarks+0x1e/0x30 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951048]  [<ffffffffc02e5441>] haswell_crtc_enable+0x321/0x8c0 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951061]  [<ffffffffc02d1ace>] ? intel_finish_crtc_commit+0xe/0x10 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951072]  [<ffffffffc017b324>] ? drm_atomic_helper_commit_planes_on_crtc+0x154/0x270 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951085]  [<ffffffffc02e1ded>] intel_atomic_commit+0x5dd/0xdb0 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951101]  [<ffffffffc007180e>] ? drm_atomic_check_only+0x18e/0x590 [drm]
  Apr  7 08:00:49 test kernel: [    9.951109]  [<ffffffffc0071c47>] drm_atomic_commit+0x37/0x60 [drm]
  Apr  7 08:00:49 test kernel: [    9.951113]  [<ffffffffc017c5ef>] restore_fbdev_mode+0x22f/0x260 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951121]  [<ffffffffc007046a>] ? drm_modeset_lock_all_ctx+0x9a/0xb0 [drm]
  Apr  7 08:00:49 test kernel: [    9.951125]  [<ffffffffc017e7d3>] drm_fb_helper_restore_fbdev_mode_unlocked+0x33/0x80 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951128]  [<ffffffffc017e84d>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951131]  [<ffffffffc017e752>] drm_fb_helper_hotplug_event+0xd2/0x120 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951134]  [<ffffffffc017e7f6>] drm_fb_helper_restore_fbdev_mode_unlocked+0x56/0x80 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951136]  [<ffffffffc017e84d>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
  Apr  7 08:00:49 test kernel: [    9.951150]  [<ffffffffc02f79aa>] intel_fbdev_set_par+0x1a/0x60 [i915_bpo]
  Apr  7 08:00:49 test kernel: [    9.951151]  [<ffffffff8146b2b6>] fb_set_var+0x236/0x460
  Apr  7 08:00:49 test kernel: [    9.951153]  [<ffffffff810b217d>] ? select_idle_sibling+0xbd/0x120
  Apr  7 08:00:49 test kernel: [    9.951155]  [<ffffffff810b3441>] ? wakeup_preempt_entity.isra.55+0x41/0x50
  Apr  7 08:00:49 test kernel: [    9.951156]  [<ffffffff810b3e8a>] ? check_preempt_wakeup+0xfa/0x220
  Apr  7 08:00:49 test kernel: [    9.951158]  [<ffffffff814615af>] fbcon_blank+0x30f/0x350
  Apr  7 08:00:49 test kernel: [    9.951160]  [<ffffffff814f85c3>] do_unblank_screen+0xd3/0x1a0
  Apr  7 08:00:49 test kernel: [    9.951161]  [<ffffffff814edc4a>] vt_ioctl+0x50a/0x12f0
  Apr  7 08:00:49 test kernel: [    9.951167]  [<ffffffffc0056749>] ? drm_ioctl+0x189/0x540 [drm]
  Apr  7 08:00:49 test kernel: [    9.951168]  [<ffffffff814e117f>] tty_ioctl+0x35f/0xc40
  Apr  7 08:00:49 test kernel: [    9.951170]  [<ffffffff81821f79>] ? schedule_hrtimeout_range_clock+0xb9/0x1b0
  Apr  7 08:00:49 test kernel: [    9.951172]  [<ffffffff812544eb>] ? ep_poll+0x37b/0x3d0
  Apr  7 08:00:49 test kernel: [    9.951173]  [<ffffffff8121ef3f>] do_vfs_ioctl+0x29f/0x490
  Apr  7 08:00:49 test kernel: [    9.951175]  [<ffffffff810aaca0>] ? wake_up_q+0x70/0x70
  Apr  7 08:00:49 test kernel: [    9.951176]  [<ffffffff8121f1a9>] SyS_ioctl+0x79/0x90
  Apr  7 08:00:49 test kernel: [    9.951177]  [<ffffffff81822b72>] entry_SYSCALL_64_fastpath+0x16/0x71
  Apr  7 08:00:49 test kernel: [    9.951178] ---[ end trace 7e448a85359a7dca ]---

  
  Attached is the full kernel log from boot until the issue happens, at which point, if I have a lockup of X I need to reboot to get back to normal.

  I don't know if this particular bug I'm reporting is the one
  responsible for the lockups, as I've isolated 4 different
  warning/error messages which separately or in combination may be the
  cause.   I'm reporting all of them now in separate bug reports.

  Please let me know if any information is missing.

  # lspci
  00:00.0 Host bridge: Intel Corporation Sky Lake Host Bridge/DRAM Registers (rev 08)
  00:02.0 VGA compatible controller: Intel Corporation Sky Lake Integrated Graphics (rev 07)
  00:08.0 System peripheral: Intel Corporation Sky Lake Gaussian Mixture Model
  00:14.0 USB controller: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller (rev 21)
  00:14.2 Signal processing controller: Intel Corporation Sunrise Point-LP Thermal subsystem (rev 21)
  00:16.0 Communication controller: Intel Corporation Sunrise Point-LP CSME HECI (rev 21)
  00:1c.0 PCI bridge: Intel Corporation Device 9d10 (rev f1)
  00:1c.2 PCI bridge: Intel Corporation Device 9d12 (rev f1)
  00:1c.4 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port (rev f1)
  00:1f.0 ISA bridge: Intel Corporation Sunrise Point-LP LPC Controller (rev 21)
  00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
  00:1f.3 Audio device: Intel Corporation Sunrise Point-LP HD Audio (rev 21)
  00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
  00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection I219-LM (rev 21)
  02:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS522A PCI Express Card Reader (rev 01)
  04:00.0 Network controller: Intel Corporation Wireless 8260 (rev 3a)
  05:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller (rev 01)

  # lspci -vvv
  00:00.0 Host bridge: Intel Corporation Sky Lake Host Bridge/DRAM Registers (rev 08)
          Subsystem: Lenovo Skylake Host Bridge/DRAM Registers
          Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
          Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort+ >SERR- <PERR- INTx-
          Latency: 0
          Capabilities: [e0] Vendor Specific Information: Len=10 <?>

  00:02.0 VGA compatible controller: Intel Corporation Sky Lake Integrated Graphics (rev 07) (prog-if 00 [VGA controller])
          Subsystem: Lenovo Skylake Integrated Graphics
          Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
          Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
          Latency: 0
          Interrupt: pin A routed to IRQ 133
          Region 0: Memory at f0000000 (64-bit, non-prefetchable) [size=16M]
          Region 2: Memory at e0000000 (64-bit, prefetchable) [size=256M]
          Region 4: I/O ports at e000 [size=64]
          Expansion ROM at <unassigned> [disabled]
          Capabilities: [40] Vendor Specific Information: Len=0c <?>
          Capabilities: [70] Express (v2) Root Complex Integrated Endpoint, MSI 00
                  DevCap: MaxPayload 128 bytes, PhantFunc 0
                          ExtTag- RBE+
                  DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
                          RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
                          MaxPayload 128 bytes, MaxReadReq 128 bytes
                  DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend-
                  DevCap2: Completion Timeout: Not Supported, TimeoutDis-, LTR-, OBFF Not Supported
                  DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-, LTR-, OBFF Disabled
          Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
                  Address: fee00018  Data: 0000
          Capabilities: [d0] Power Management version 2
                  Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
                  Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
          Capabilities: [100 v1] #1b
          Capabilities: [200 v1] Address Translation Service (ATS)
                  ATSCap: Invalidate Queue Depth: 00
                  ATSCtl: Enable-, Smallest Translation Unit: 00
          Capabilities: [300 v1] #13
          Kernel driver in use: i915_bpo
          Kernel modules: i915_bpo

  
  # for file in /sys/module/i915_bpo/parameters/*; do echo -en $file"\t"; cat $file; done;
  /sys/module/i915_bpo/parameters/disable_display N
  /sys/module/i915_bpo/parameters/disable_power_well      1
  /sys/module/i915_bpo/parameters/edp_vswing      0
  /sys/module/i915_bpo/parameters/enable_cmd_parser       1
  /sys/module/i915_bpo/parameters/enable_dc       -1
  /sys/module/i915_bpo/parameters/enable_execlists        1
  /sys/module/i915_bpo/parameters/enable_fbc      -1
  /sys/module/i915_bpo/parameters/enable_guc_submission   N
  /sys/module/i915_bpo/parameters/enable_hangcheck        Y
  /sys/module/i915_bpo/parameters/enable_ips      1
  /sys/module/i915_bpo/parameters/enable_ppgtt    3
  /sys/module/i915_bpo/parameters/enable_psr      0
  /sys/module/i915_bpo/parameters/enable_rc6      1
  /sys/module/i915_bpo/parameters/fastboot        N
  /sys/module/i915_bpo/parameters/guc_log_level   -1
  /sys/module/i915_bpo/parameters/invert_brightness       0
  /sys/module/i915_bpo/parameters/load_detect_test        N
  /sys/module/i915_bpo/parameters/lvds_channel_mode       0
  /sys/module/i915_bpo/parameters/lvds_use_ssc    -1
  /sys/module/i915_bpo/parameters/mmio_debug      0
  /sys/module/i915_bpo/parameters/modeset -1
  /sys/module/i915_bpo/parameters/nuclear_pageflip        N
  /sys/module/i915_bpo/parameters/panel_ignore_lid        1
  /sys/module/i915_bpo/parameters/prefault_disable        N
  /sys/module/i915_bpo/parameters/preliminary_hw_support  0
  /sys/module/i915_bpo/parameters/reset   Y
  /sys/module/i915_bpo/parameters/semaphores      -1
  /sys/module/i915_bpo/parameters/use_mmio_flip   0
  /sys/module/i915_bpo/parameters/vbt_sdvo_panel_type     -1
  /sys/module/i915_bpo/parameters/verbose_state_checks    Y
  --- 
  ApportVersion: 2.20.1-0ubuntu2.1
  Architecture: amd64
  DistroRelease: Ubuntu 16.04
  InstallationDate: Installed on 2016-04-03 (63 days ago)
  InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Beta amd64 (20160401)
  Package: linux (not installed)
  Tags:  xenial
  Uname: Linux 4.6.0-040600rc7-generic x86_64
  UnreportableReason: The running kernel is not an Ubuntu kernel
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups:
   
  _MarkForUpload: True

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References