[Bug 91434] [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

--- Comment #14 from Martin Andersen <martin.x.andersen at gmail.com> ---
Reinstalled system to 14.04.3 to eliminate any quirks and re-ran tests w/
drm.debug=0xe and xf86-video-intel driver (2.99.917), compiled with
'--enable-debug=full' using three kernel revisions as a base:

- The previously known-good 3.13.5
- The 14.04.3 default kernel 3.19.0
- Current bleeding edge 4.4.4 kernel from
http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.4.4-wily/


Steps performed:

System booted w/ extra kernel flags, user logged in and modes for HDMI2 are
attempted modified as follows:

- Switch HDMI2 to 24Hz
- Switch HDMI2 to 30Hz
- Switch HDMI2 to 50Hz
- Switch HDMI2 to 60Hz (default)

Desktop envs tested are plain Gnome (non-DE) session, MATE session (worked
perfectly in 3.13.5 & 3.18.5 (on 2nd IVB system) and XFCE4. They all behave the
same.


Results:

3.13.5:

All modes are switched correctly. Subsequently an extra step is performed;
starting Kodi and launching a movie in 24Hz-> plays correctly. No 23.976 mode
tested as it requires a custom modeline (never worked OOB on Intel for either
systems)

3.19.0:

Only the 60Hz mode is output. The rest produce no signal.

4.4.4:

Same as 3.19, with the exception of graphical artifacts (green pixel dots)
randomly showing in the output.

Logs: (Dropboxed as it's a PITA to upload these to freedesktop due to its low
size limits)

3.13.5:
syslog:    
https://www.dropbox.com/s/cvbd8l8zmb3x8hg/syslog-3.13.5.working.txt.xz?dl=0
Xorg.0.log:
https://www.dropbox.com/s/60um14d14qushoc/xorg.0.log.3.13.5.working.txt.xz?dl=0

3.19.0:
syslog:    
https://www.dropbox.com/s/auci5afmo4cid38/syslog-3.19.0.defunct.txt.xz?dl=0
Xorg.0.log:
https://www.dropbox.com/s/dhsokec7hgz0ttj/xorg.0.log.3.19.0.defunct.txt.xz?dl=0

4.4.4:

syslog:    
https://www.dropbox.com/s/nztrvartf10u6dm/syslog-4.4.4.defunct.txt.xz?dl=0
Xorg.0.log:
https://www.dropbox.com/s/02j3tdlhld4d2f6/xorg.0.log.4.4.4.defunct.txt.xz?dl=0

I sincerely hope enough debug output has now been provided in order to properly
diagnose the issue (it took most of my day to get the new test platform up and
running.)

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