[Bug 101639] New: [KBL] External display pixelated after upgrade to kernel >= 4.11.0-rc1

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101639

            Bug ID: 101639
           Summary: [KBL] External display pixelated after upgrade to
                    kernel >= 4.11.0-rc1
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: njkkow at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 132331
  --> https://bugs.freedesktop.org/attachment.cgi?id=132331&action=edit
configs, dmesg w/ drm.debug=0xe, EDIDs, fb0 sysfs, inxi, Xorg.0.log, picture of
screen

I have a Thinkpad X270 with an i7 7500U / Intel HD Graphics 620, running Fedora
25, Mint, and Xubuntu (attachments are from Xubuntu.)  I had been using a 26"
Vizio E261VA TV over HDMI as an external monitor for a few months without any
issues, but after upgrading to any kernel >= 4.11.0-rc1, the display becomes
very pixelated and text is almost unreadable.  On 4.10 it looks fine.  One
thing I noticed was that the "mode" for the fb0 device is now set to
"U:1360x768p-0".  In the working kernel it's "U:1920x1080p-0".  The issue only
happens over HDMI; the picture still looks fine if I use a USB-C -> VGA
adapter.

The native resolution for this TV is 1360x768, which is the resolution I run it
at, and the laptop screen is running at 1920x1080.  I have tried uninstalling
the Xorg intel driver but it didn't make a difference.  I have also tried
booting the kernel with the parameter video=HDMI-A-2:1920x1080M at 60.  That will
change the framebuffer mode back to what it was in 4.10, but I still can't seem
to get the pixelation to go away.  I tried to force the EDID from VGA using
drm_kms_helper but it didn't help either.  I built a kernel from
cgit.freedesktop.org/drm-tip today (6/28/17) and I still see the issue. 
Attached the configs I am using for 4.10 and the drm-tip kernel.

I noticed quite a few changes in the logs for 4.11.0-rc1 involving drm/i915,
framebuffers, EDID, and HDMI, so I assume this has something to do with that. 
I'm not 100% sure it involves the framebuffer, but the resolution change caught
my eye.  I see the pixelation before X even starts, while the startup checks
are running down the screen.

Please let me know if I can provide any other info.  Thanks!

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