[Bug 96828] New: Cannot set 4K screen to 60Hz on xf86-video-intel driver: CPU pipe B FIFO underrun

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=96828

            Bug ID: 96828
           Summary: Cannot set 4K screen to 60Hz on xf86-video-intel
                    driver: CPU pipe B FIFO underrun
           Product: xorg
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Driver/intel
          Assignee: chris at chris-wilson.co.uk
          Reporter: bugs.freedesktop.org at r123.de
        QA Contact: intel-gfx-bugs at lists.freedesktop.org

On a Thinkpad T460p with Intel graphics, I cannot set a monitor to the
resolution 3840x2160 @60Hz. 3840x2160 only works at 30Hz. Modesetting to @60Hz
works, but the screen stays blank. Applies to MiniDP, DisplayPort and HDMI,
both on laptop and UltraDock docking station.

When setting to @60Hz the following stacktrace occurs on dmesg:

[  154.746359] ------------[ cut here ]------------
[  154.746371] WARNING: CPU: 3 PID: 1497 at
drivers/gpu/drm/i915/intel_display.c:13929 skl_max_scale.part.100+0x6a/0x80
[  154.746374] WARN_ON_ONCE(!crtc_clock || cdclk < crtc_clock)
[  154.746376] Modules linked in:
[  154.746378]  ccm rfcomm acpi_call(O) bnep twofish_x86_64_3way lrw
glue_helper twofish_x86_64 twofish_common dm_crypt dm_mod loop fuse btusb btrtl
btbcm btintel bluetooth arc4 iwlmvm mac80211 rtsx_pci_sdmmc kvm_intel mmc_core
kvm irqbypass iwlwifi input_leds rtsx_pci cfg80211 mfd_core mei_me mei
thinkpad_acpi led_class
[  154.746410] CPU: 3 PID: 1497 Comm: X Tainted: G           O    4.6.0-gentoo
#3
[  154.746412] Hardware name: LENOVO 20FWCTO1WW/20FWCTO1WW, BIOS R07ET63W (2.03
) 03/15/2016
[  154.746414]  0000000000000000 ffff88042b11ba30 ffffffff81299908
ffff88042b11ba80
[  154.746419]  0000000000000000 ffff88042b11ba70 ffffffff81052e0c
0000366900000870
[  154.746423]  ffff88009c014b40 ffff88042fa93400 ffff88042fce2000
ffff88042fa93400
[  154.746427] Call Trace:
[  154.746433]  [<ffffffff81299908>] dump_stack+0x4d/0x65
[  154.746439]  [<ffffffff81052e0c>] __warn+0xcc/0xf0
[  154.746444]  [<ffffffff81052e7a>] warn_slowpath_fmt+0x4a/0x50
[  154.746447]  [<ffffffff8140af7a>] skl_max_scale.part.100+0x6a/0x80
[  154.746451]  [<ffffffff8140b04b>] intel_check_primary_plane+0xbb/0xd0
[  154.746455]  [<ffffffff813fddd9>] intel_plane_atomic_check+0x129/0x1f0
[  154.746461]  [<ffffffff813737f3>] drm_atomic_helper_check_planes+0x43/0x1d0
[  154.746466]  [<ffffffff81417606>] intel_atomic_check+0x2f6/0x1180
[  154.746471]  [<ffffffff816dbd01>] ? __ww_mutex_lock_slowpath+0x111/0x1b0
[  154.746476]  [<ffffffff81396bee>] drm_atomic_check_only+0x13e/0x640
[  154.746480]  [<ffffffff813964a2>] ?
drm_atomic_set_crtc_for_connector+0x52/0xe0
[  154.746484]  [<ffffffff81397102>] drm_atomic_commit+0x12/0x50
[  154.746489]  [<ffffffff81374fc6>] drm_atomic_helper_set_config+0x76/0xb0
[  154.746494]  [<ffffffff81387d1d>] drm_mode_set_config_internal+0x5d/0xf0
[  154.746498]  [<ffffffff8138b553>] drm_mode_setcrtc+0x183/0x4e0
[  154.746502]  [<ffffffff8137d67d>] drm_ioctl+0x13d/0x560
[  154.746506]  [<ffffffff8138b3d0>] ? drm_mode_setplane+0x1b0/0x1b0
[  154.746512]  [<ffffffff81185ba9>] do_vfs_ioctl+0x89/0x580
[  154.746516]  [<ffffffff8105f08d>] ? __set_task_blocked+0x2d/0x70
[  154.746521]  [<ffffffff81175a6c>] ? __sb_end_write+0x1c/0x20
[  154.746524]  [<ffffffff81061621>] ? __set_current_blocked+0x31/0x50
[  154.746529]  [<ffffffff811860dc>] SyS_ioctl+0x3c/0x70
[  154.746532]  [<ffffffff81061881>] ? SyS_rt_sigprocmask+0x81/0xa0
[  154.746536]  [<ffffffff816de09b>] entry_SYSCALL_64_fastpath+0x13/0x8f
[  154.746539] ---[ end trace a530255cd499b6af ]---
[  154.762344] [drm:intel_cpu_fifo_underrun_irq_handler] *ERROR* CPU pipe B
FIFO underrun

Reproducible on Gentoo Linux with kernel 4.6.0 and
xf86-video-intel-2.99.917_p20160621

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