[Bug 91434] [IVB/HSW] 23.976Hz & 24Hz modes broken on dual-display with recent (4.0.x) kernels

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91434

Martin Andersen <martin.x.andersen at gmail.com> changed:

           What    |Removed                     |Added
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             Status|NEEDINFO                    |ASSIGNED

--- Comment #50 from Martin Andersen <martin.x.andersen at gmail.com> ---
Hi Lakshmi,

Added logs from one of my Haswell systems running the latest - as of today -
DRM tip kernel 4.19.0-994 for your viewing pleasure.

Exactly the same behaviour as on my Ivy Bridge is witnessed - no output during
boot, no output at all from 50 & 60 Hz modes, and garbled text from the 23.976
& 24.000Hz modes which all work correctly on the 3.x branch.

Steps performed after login -

$ xrandr -q
$ xrandr --output HDMI2 --mode 1920x1080 --rate 23.976
$ xrandr --output HDMI2 --mode 1920x1080 --rate 24
$ xrandr --output HDMI2 --mode 1920x1080 --rate 50
$ xrandr --output HDMI2 --mode 1920x1080 --rate 60

$ xrandr --output HDMI2 --mode 1920x1080 --rate 23.976
$ xrandr --output HDMI2 --mode 1920x1080 --rate 24
$ xrandr --output HDMI2 --mode 1920x1080 --rate 50
$ xrandr --output HDMI2 --mode 1920x1080 --rate 60

The cynic in me suspects that this ticket will now lay dormant again for a few
months, whereupon I will again be asked to provide output from the latest DRM
tip kernel (as if hoping that it magically solved this without any specific
changes for this issue having been made)

If so is the case, *please* refer to a patch which - potentially - restores
this functionality so that there is at least a inkling that it might behave
differently.
It has previously been suggested that this is due to "newer" kernels not
defaulting to 8bpc.

And before Intel again points to issues with "dongles, cables, sources & sinks"
bear in mind that these have all been eliminated.

- By hooking up directly, bypassing any switches
- Loss of signal is occurring with three separate systems/sources - one IVB,
two HSW
- All cables have been replaced
- There are no dongles in between
- Sinks have been replaced also

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