Hibernating (using systemd/uswsusp/pm-hibernate) randomly results in a blank (no backlight) screen upon resume. After many months of struggling to find any useful info for this problem, I followed basic-pm-debugging instructions (https://www.kernel.org/doc/Documentation/power/basic-pm-debugging.txt) and found this. I'm not entirely sure if this is the root cause (or even indeed the only cause) of the blank screen issue, but figured I'd report it anyway. (here is the input) # echo devices > /sys/power/pm_test # echo shutdown > /sys/power/disk # echo disk > /sys/power/state (from dmesg) [ 558.657591] ------------[ cut here ]------------ [ 558.657603] WARNING: CPU: 0 PID: 1880 at drivers/gpu/drm/i915/intel_uncore.c:620 hsw_unclaimed_reg_debug+0x69/0x90 [i915]() [ 558.657605] Unclaimed register detected after writing to register 0x71414 [ 558.657606] Modules linked in: joydev mousedev tpm_infineon arc4 snd_hda_codec_realtek snd_hda_codec_generic iTCO_wdt iTCO_vendor_support ppdev hp_wmi sparse_keymap mxm_wmi intel_rapl iosf_mbi x86_pkg_temp_thermal intel_powerclamp coretemp iwlmvm kvm_intel kvm mac80211 crct10dif_pclmul crc32_pclmul aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd pcspkr iwlwifi input_leds psmouse serio_raw snd_hda_intel btusb btrtl snd_hda_codec uvcvideo rtsx_pci_ms btbcm cfg80211 videobuf2_vmalloc btintel snd_hda_core memstick videobuf2_memops snd_hwdep bluetooth videobuf2_core v4l2_common videodev i2c_i801 lpc_ich e1000e rfkill snd_pcm media snd_timer snd mei_me ie31200_edac parport_pc ptp mei edac_core shpchp pps_core parport soundcore battery thermal hp_accel led_class lis3lv02d wmi input_polldev [ 558.657633] tpm_tis evdev tpm hp_wireless mac_hid fjes ac processor sch_fq_codel nfs lockd grace sunrpc fscache acpi_call(O) ip_tables x_tables ext4 crc16 mbcache jbd2 sr_mod cdrom sd_mod rtsx_pci_sdmmc mmc_core atkbd libps2 crc32c_intel ahci libahci libata scsi_mod rtsx_pci xhci_pci ehci_pci xhci_hcd ehci_hcd usbcore usb_common i8042 serio i915 video button i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm intel_agp intel_gtt [ 558.657655] CPU: 0 PID: 1880 Comm: kworker/u16:77 Tainted: G O 4.3.3-2-ARCH #1 [ 558.657656] Hardware name: Hewlett-Packard HP Zbook 17 G2/2255, BIOS M70 Ver. 01.12 09/23/2015 [ 558.657660] Workqueue: events_unbound async_run_entry_fn [ 558.657661] 0000000000000000 000000002b1d4e65 ffff88082d2e7bd0 ffffffff812c0dc9 [ 558.657662] ffff88082d2e7c18 ffff88082d2e7c08 ffffffff81074f42 ffff880887230000 [ 558.657664] 0000000000071414 ffff880887230080 0000000000000000 ffff880887230078 [ 558.657665] Call Trace: [ 558.657670] [<ffffffff812c0dc9>] dump_stack+0x4b/0x72 [ 558.657672] [<ffffffff81074f42>] warn_slowpath_common+0x82/0xc0 [ 558.657674] [<ffffffff81074fdc>] warn_slowpath_fmt+0x5c/0x80 [ 558.657679] [<ffffffffa0130359>] hsw_unclaimed_reg_debug+0x69/0x90 [i915] [ 558.657683] [<ffffffffa0136d97>] hsw_write32+0x97/0x150 [i915] [ 558.657687] [<ffffffffa00ea099>] i915_restore_state+0x149/0x3a0 [i915] [ 558.657690] [<ffffffffa00df139>] i915_drm_resume+0x39/0x150 [i915] [ 558.657693] [<ffffffffa00df275>] i915_pm_resume+0x25/0x30 [i915] [ 558.657696] [<ffffffff81306e69>] pci_pm_restore+0x79/0xb0 [ 558.657697] [<ffffffff81306df0>] ? pci_pm_suspend_noirq+0x180/0x180 [ 558.657701] [<ffffffff813ec02e>] dpm_run_callback+0x4e/0x130 [ 558.657702] [<ffffffff813ec5c3>] device_resume+0xd3/0x1f0 [ 558.657704] [<ffffffff813ec6fd>] async_resume+0x1d/0x50 [ 558.657705] [<ffffffff81095598>] async_run_entry_fn+0x48/0x150 [ 558.657708] [<ffffffff8108cfeb>] process_one_work+0x14b/0x440 [ 558.657709] [<ffffffff8108d328>] worker_thread+0x48/0x4a0 [ 558.657710] [<ffffffff8108d2e0>] ? process_one_work+0x440/0x440 [ 558.657712] [<ffffffff81092e68>] kthread+0xd8/0xf0 [ 558.657713] [<ffffffff81092d90>] ? kthread_worker_fn+0x170/0x170 [ 558.657715] [<ffffffff8158409f>] ret_from_fork+0x3f/0x70 [ 558.657716] [<ffffffff81092d90>] ? kthread_worker_fn+0x170/0x170 [ 558.657717] ---[ end trace 2f6eca7a9bf74f82 ]---
Please file new i915 bugs at the freedesktop.org bugzilla at https://bugs.freedesktop.org/enter_bug.cgi?product=DRI&component=DRM/Intel