[Bug 93980] New: blank screen at 4k at 60Hz DP 1.2

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93980

            Bug ID: 93980
           Summary: blank screen at 4k at 60Hz DP 1.2
           Product: DRI
           Version: XOrg git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: alinm.elena at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

So I try to connect my external display to my dell xps 9350 skylake

works fine with DP1.1 3840x2160 at 30.00
However if I move to DPI1.2 while xrandr reports the 60Hz as available and
prefered, trying to select it results in a blank screen and this error in log
[14888.696042] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU
pipe B FIFO underrun

this is with 4.5.0-rc1-2.gc7bac4c
there is a kernel trace in logs but i think is unrelated to the aformentioned
error.

[ 2441.732603] [drm:intel_dp_start_link_train [i915]] *ERROR* 5.4 Gbps link
rate without HBR2/TPS3 support
[ 2441.736534] [drm] Reducing the compressed framebuffer size. This may lead to
less power savings than a non-reduced-size. Try to increase stolen memory size
if available in BIOS.
[ 2441.999859] ------------[ cut here ]------------
[ 2441.999896] WARNING: CPU: 2 PID: 2188 at
../drivers/gpu/drm/i915/intel_pm.c:3544 skl_update_other_pipe_wm+0x14d/0x150
[i915]()
[ 2441.999897] WARN_ON(!wm_changed)
[ 2441.999898] Modules linked in:
[ 2441.999900]  fuse hidp cmac ecb rfcomm af_packet bnep hid_generic btusb
btrtl uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core
usbhid videodev hid_multitouch snd_hda_codec_hdmi dell_led
snd_hda_codec_realtek snd_hda_codec_generic nls_iso8859_1 snd_hda_intel
nls_cp437 x86_pkg_temp_thermal intel_powerclamp coretemp vfat snd_hda_codec fat
snd_hda_core snd_hwdep kvm_intel snd_pcm kvm irqbypass crct10dif_pclmul
crc32_pclmul brcmfmac dell_laptop rtsx_pci_ms brcmutil snd_timer dcdbas
i2c_designware_platform ghash_clmulni_intel i2c_designware_core aesni_intel
dell_wmi cfg80211 memstick aes_x86_64 snd lrw gf128mul glue_helper ablk_helper
cryptd idma64 pcspkr joydev mei_me hci_uart soundcore i2c_i801 virt_dma btbcm
shpchp mei btqca btintel intel_lpss_pci processor_thermal_device
intel_soc_dts_iosf
[ 2441.999941]  thermal fan bluetooth rfkill pinctrl_sunrisepoint pinctrl_intel
intel_lpss_acpi intel_lpss int3400_thermal int3403_thermal acpi_thermal_rel
int340x_thermal_zone battery wmi intel_hid acpi_pad ac acpi_als tpm_tis
sparse_keymap kfifo_buf tpm industrialio i915 rtsx_pci_sdmmc mmc_core
crc32c_intel i2c_algo_bit xhci_pci drm_kms_helper syscopyarea sysfillrect
sysimgblt xhci_hcd fb_sys_fops serio_raw drm rtsx_pci nvme mfd_core usbcore
usb_common video i2c_hid button fjes sg efivarfs
[ 2441.999969] CPU: 2 PID: 2188 Comm: X Tainted: G     U  W      
4.5.0-rc1-2.gc7bac4c-default #1
[ 2441.999971] Hardware name: Dell Inc. XPS 13 9350/0VM5NC, BIOS 1.2.3
01/08/2016
[ 2441.999972]  ffffffffa03b5700 ffff88046e2ff988 ffffffff81390cb9
ffff88046e2ff9d0
[ 2441.999975]  ffff88046e2ff9c0 ffffffff8107c712 ffff88046e2ffa44
ffff88046a379bd4
[ 2441.999977]  ffff88046aa9e000 ffff88005ebf1b78 ffff88046b5ad000
ffff88046e2ffa20
[ 2441.999980] Call Trace:
[ 2441.999988]  [<ffffffff8101a115>] try_stack_unwind+0x175/0x190
[ 2441.999995]  [<ffffffff81019069>] dump_trace+0x69/0x3a0
[ 2441.999999]  [<ffffffff8101a17b>] show_trace_log_lvl+0x4b/0x60
[ 2442.000002]  [<ffffffff810194ac>] show_stack_log_lvl+0x10c/0x180
[ 2442.000005]  [<ffffffff8101a215>] show_stack+0x25/0x50
[ 2442.000010]  [<ffffffff81390cb9>] dump_stack+0x4b/0x72
[ 2442.000015]  [<ffffffff8107c712>] warn_slowpath_common+0x82/0xc0
[ 2442.000020]  [<ffffffff8107c79c>] warn_slowpath_fmt+0x4c/0x50
[ 2442.000032]  [<ffffffffa02f047d>] skl_update_other_pipe_wm+0x14d/0x150
[i915]
[ 2442.000047]  [<ffffffffa02f05e3>] skl_update_wm+0x163/0x630 [i915]
[ 2442.000060]  [<ffffffffa02f3e2e>] intel_update_watermarks+0x1e/0x30 [i915]
[ 2442.000081]  [<ffffffffa035cf11>] haswell_crtc_enable+0x321/0x8c0 [i915]
[ 2442.000102]  [<ffffffffa0359bf4>] intel_atomic_commit+0x694/0xac0 [i915]
[ 2442.000120]  [<ffffffffa0189067>] drm_atomic_commit+0x37/0x60 [drm]
[ 2442.000129]  [<ffffffffa026e586>] drm_atomic_helper_set_config+0x76/0xb0
[drm_kms_helper]
[ 2442.000141]  [<ffffffffa0178682>] drm_mode_set_config_internal+0x62/0x100
[drm]
[ 2442.000154]  [<ffffffffa017ce5d>] drm_mode_setcrtc+0x3cd/0x4e0 [drm]
[ 2442.000163]  [<ffffffffa016e712>] drm_ioctl+0x152/0x540 [drm]
[ 2442.000167]  [<ffffffff8121a912>] do_vfs_ioctl+0x92/0x580
[ 2442.000171]  [<ffffffff8121ae79>] SyS_ioctl+0x79/0x90
[ 2442.000175]  [<ffffffff816c50f6>] entry_SYSCALL_64_fastpath+0x16/0x75
[ 2442.001869] DWARF2 unwinder stuck at entry_SYSCALL_64_fastpath+0x16/0x75

[ 2442.001872] Leftover inexact backtrace:

[ 2442.001875] ---[ end trace a05b3ea76533043e ]---

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