PROBLEM: Asus C201 video mode problems on HDMI hotplug (regression)

[Nick Bowler <nbowler@draconx.ca>]

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Hi,

On my Asus C201 laptop (rk3288) the HDMI has been behaving weirdly after
Linux upgrade.

~50% of the time after a hotplug, there is a vertical pink bar on the
left of the display area and audio is not working at all.  According to
the sink device the display size is 1282x720 which seems pretty wrong
(normal and working situation is 1280x720).

I posted photos of non-working versus working states here:

  https://imgur.com/a/qhAZG

Unplugging and plugging the cable again will correct the issue (it seems
to, for the most part, alternate between working and not-working states,
although not always).  It always works on power up with the cable initially
connected.

This is a regression from 4.11, where hotplug works perfectly every time.

I attached dmesg output (gzipped) from 4.14-rc7 (I booted up and
re-plugged the cable twice, which triggered non-working state and then
back to working state -- although seems no messages are logged from
these hotplugs).

I am working to bisect this, might take a while.  Partial progress
follows...

Let me know of anything else I should try.

Thanks,
  Nick

git bisect start
# bad: [0b07194bb55ed836c2cc7c22e866b87a14681984] Linux 4.14-rc7
git bisect bad 0b07194bb55ed836c2cc7c22e866b87a14681984
# bad: [fa394784e74b918f44fca1e6a1f826cf818350d2] Linux 4.12.14
git bisect bad fa394784e74b918f44fca1e6a1f826cf818350d2
# good: [bd1a9eb6a755e1cb342725a11242251d2bfad567] Linux 4.11.12
git bisect good bd1a9eb6a755e1cb342725a11242251d2bfad567
# good: [a351e9b9fc24e982ec2f0e76379a49826036da12] Linux 4.11
git bisect good a351e9b9fc24e982ec2f0e76379a49826036da12
# bad: [8f28472a739e8e39adc6e64ee5b460df039f0e4f] Merge tag
'usb-4.12-rc1' of
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb
git bisect bad 8f28472a739e8e39adc6e64ee5b460df039f0e4f

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