[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

--- Comment #22 from Martin Andersen <martin.x.andersen at gmail.com> ---
Added more drm.debug=0xe output from my Haswell test system.

In short; the xorg.conf provided 23.976Hz mode (Modeline "1920x1080 at 23.97610" 
74.230 1920 2560 2604 2752 1080 1084 1089 1125 +hsync +vsync) never works with
any recent kernel/xserver-xorg-video-intel combo.

On 4.x the 2.99.917 driver is never able to select the mode, outputting
everything in 24.000Hz. Moreover, half the time it tries to select the mode the
secondary screen (HDMI2, going to the Epson PJ), goes blank. From the logs
everything is switched fine, but the signal being output is incompatible with
the display.

When reverting to the (ancient) 2.21.9 version of xserver-xorg-video-intel
(intel_drv.so) - the Haswell system is able to switch to the provided 23.976Hz
mode.

Has there been some changes wrt. mode-validation / edid-probing with the newer
2.99.x drivers? It almost appears so, since despite my numerous tests I cannot
get the correct mode to work with them.

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