[Bug 110047] New: Bad 4kp60 modeset over HDMI

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=110047

            Bug ID: 110047
           Summary: Bad 4kp60 modeset over HDMI
           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: freddie at witherden.org
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

I have an Intel NUC NUC6i7KYK and an AOC U3277PWQU monitor.  Under Linux
4.14.13 both DisplayPort and HDMI outputs work as expected.  However, after
updating to Linux 5.0.1 there appears to be a regression in how the mode is set
over HDMI.

During the boot process the BIOS sets the resolution to 3840*2160 which carries
over the GRUB.  After the kernel loads the resolution is temporarily reduced to
~VGA until mode setting kicks in and sets the resolution back to 3840*2160. 
Using HDMI on Linux 5.0.1 this mode set appears to go awry.  Although the
resolution is correct (4kp60) the console background (which should be black)
turns blue and the text (which should be white) develops colour fringes.  The
issue persists even after the desktop loads (which takes on an almost greyscale
appearance). 

As such it appears as if there has been a regression in the kernel mode driver
somewhere between 4.4.13 and 5.0.1.

I appreciate that this is a somewhat vague report and so please let me know
what specific details are required on my end in order to further debug this
issue.

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