External display pixelated after upgrade to kernel >= 4.11.0-rc1

[neil k <njkkow@xxxxxxxxx>]

Hey everyone,

I have a new Thinkpad with a Kaby Lake CPU and Intel HD Graphics 620.  I had been using a 26" Vizio TV (1360x768) over HDMI as an external monitor with no issues.  I upgraded to a 4.11 series kernel and now the TV is very pixelated (see attached picture.)  I posted some logs/info on the kernel bugzilla here.  I had to nuke that Fedora install, but I have attached dmesg logs from Xubuntu booted with the drm.debug=0xe option.  Xubuntu logs are with the laptop screen at 1600x900.

Here's what I've found so far in addition to the bugzilla post:

- TV still works if I use a USB-C to VGA adapter instead of HDMI. 

- Still see the issue if I force HDMI-A-2 to use the EDID extracted from VGA, which has no HD modelines

- I compiled a nightly kernel from

git://anongit.freedesktop.org/git/drm-intel a few days ago with no change (see dmesg attachment)

Is this is a known issue, or does anyone have any ideas about what changed in 4.11.0-rc1 that could have caused this?  I see a lot of changes for the i915 driver were made in that kernel version.  If I can provide anything else to help investigate, please let me know.

Thanks,

Neil

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