commit f0521558a2a8 ("drm/i915: Don't clobber M/N values during fastset
check") may have helped here.

Looks like that one should be in 5.1.15+ or 5.2+. What's the most recent
kernel people have tried here?

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https://bugs.launchpad.net/bugs/1785912

Title:
  Horizontal screen flicker Intel UHD graphics 620 (rev 07) Lenovo
  Ideapad 720s 13IKB 81BV

Status in Linux:
  Incomplete
Status in linux package in Ubuntu:
  Incomplete

Bug description:
  Horrible screen flicker from login screen and after login.  18.04.1 LTS.
  I have two similar laptops, both Lenovo Ideapad 720s 13IKB,
  model 81A8 - Core i5 7200U - Intel HD Graphics 620 Rev 02 - works fine.
  model 81BV - Core i5 8250U - Intel UHD Graphics 620 Rev 07 - awful screen 
flashing.

  Neither have the problem in Windows (ie hardware fine)

  I installed the standard Ubuntu 18.04 on each of them (same USB Key,
  few weeks apart) but only the 81BV / 8th gen / UHD 620 Rev 07 has the
  problem.

  Flickering visible on video here:
  https://photos.app.goo.gl/HCN73q1nQfgstgVBA

  I've used ubuntu-bug so I believe you have all the details of the
  machine.  The install came straight from your standard 18.04 download.
  Any changes are due to me trying to fix this (not much prev exp of
  kernel params etc)

  Things tried but which didn't work were:
  - enable huc/guc (got it to load - it's now visible in the attached dmesg - 
but didn't help.)
  - enable_rc6=0 (just stopped sleep / resume working)
  - edp_vswing=2

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: xserver-xorg-video-intel 2:2.99.917+git20171229-1
  ProcVersionSignature: Ubuntu 4.15.0-30.32-generic 4.15.18
  Uname: Linux 4.15.0-30-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.2
  Architecture: amd64
  CompositorRunning: None
  Date: Tue Aug  7 23:09:14 2018
  DistUpgraded: Fresh install
  DistroCodename: bionic
  DistroVariant: ubuntu
  ExtraDebuggingInterest: Yes, if not too technical
  GraphicsCard:
   Intel Corporation UHD Graphics 620 [8086:5917] (rev 07) (prog-if 00 [VGA 
controller])
     Subsystem: Lenovo UHD Graphics 620 [17aa:39af]
  InstallationDate: Installed on 2018-08-06 (1 days ago)
  InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
  Lsusb:
   Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
   Bus 001 Device 004: ID 0cf3:e500 Atheros Communications, Inc.
   Bus 001 Device 003: ID 5986:210d Acer, Inc
   Bus 001 Device 002: ID 06cb:0081 Synaptics, Inc.
   Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
  MachineType: LENOVO 81BV
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   LANG=en_GB.UTF-8
   SHELL=/bin/bash
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-30-generic 
root=UUID=10eb4e00-26e4-4f42-b983-9a603a658f89 ro i915.enable_guc=3 
i915.enable_guc_loading=1
  SourcePackage: xserver-xorg-video-intel
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 05/02/2018
  dmi.bios.vendor: LENOVO
  dmi.bios.version: 6MCN27WW
  dmi.board.asset.tag: NO Asset Tag
  dmi.board.name: LNVNB161216
  dmi.board.vendor: LENOVO
  dmi.board.version: SDK0J40709 WIN
  dmi.chassis.asset.tag: NO Asset Tag
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: Lenovo ideapad 720S-13IKB
  dmi.modalias: 
dmi:bvnLENOVO:bvr6MCN27WW:bd05/02/2018:svnLENOVO:pn81BV:pvrLenovoideapad720S-13IKB:rvnLENOVO:rnLNVNB161216:rvrSDK0J40709WIN:cvnLENOVO:ct10:cvrLenovoideapad720S-13IKB:
  dmi.product.family: ideapad 720S-13IKB
  dmi.product.name: 81BV
  dmi.product.version: Lenovo ideapad 720S-13IKB
  dmi.sys.vendor: LENOVO
  version.compiz: compiz N/A
  version.libdrm2: libdrm2 2.4.91-2
  version.libgl1-mesa-dri: libgl1-mesa-dri 18.0.5-0ubuntu0~18.04.1
  version.libgl1-mesa-glx: libgl1-mesa-glx 18.0.5-0ubuntu0~18.04.1
  version.xserver-xorg-core: xserver-xorg-core 2:1.19.6-1ubuntu4
  version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
  version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:18.0.1-1
  version.xserver-xorg-video-intel: xserver-xorg-video-intel 
2:2.99.917+git20171229-1
  version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2

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