[Bug 100885] [SNB] Blank screen after cycling HDMI receiver input

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=100885

--- Comment #19 from Matt Horan <matt at matthoran.com> ---
(In reply to Matt Horan from comment #18)
> (In reply to Ville Syrjala from comment #17)
> > We now have the properly to limite the bpc.
> > 
> > xrandr --output <whatever> --set 'max bpc' 8
> > 
> > Does that help?
> 
> Does this require a specific kernel version and/or xrandr version? Happy to
> give it a shot.

I discovered that all that is needed is a kernel that supports the 'max bpc'
prop, so I installed kernel 5.0.2. I successfully set max bpc to 8 when the
display was working. However, when switching to another input and then back,
the screen was blank. I could no longer set max bpc. xrandr --props showed max
bpc of 12. If I tried to set max bpc to 8, the setting was seemingly ignored,
and the screen remained blank.

I also tested with a newer Haswell machine, running both Windows and Linux. On
Windows, I could not reproduce the issue. On Linux, I could not reproduce the
issue as reliably, but it did occur. Interestingly, switching inputs a second
time would resolve the issue. This is not a viable solution, however, as I do
not plan to replace my SNB system any time soon (and something still seems
broken.)

The only difference I noticed between Windows and Linux is that Windows never
switched the display to 12bpc. I could not find an option in Windows to cause
this to happen.

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