[Bug 89110] Reproducible black screen glitches on DVI monitor with specific image using passive DP-DVI adaptor

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89110

--- Comment #8 from Chris Bainbridge <chris.bainbridge at gmail.com> ---
This is the adaptor:
http://www.ebay.co.uk/itm/Mini-Display-Port-to-DVI-I-Monitor-Adaptor-Converter-Cable-DisplayPort-24-5-/271098976593

The description says:

    Support Mini DisplayPort 1.1a compliant receiver offering 5.4Gbps bandwidth
over 2 lanes.
    • Support video resolution 1080p, Supports 1920 x 1200 reduced blanking
video resolution.
    • Powered from MiniDisplay source.
    • Compatibility: iMac, Mac Mini, Mac Pro, MacBook Air, MacBook Pro 13 inch,
MacBook Pro 15 inch, MacBook Pro 17 inch.
    • Connectors: Mini Display Port Male to DVI-I Female 15cm. (Length includes
connectors) 

Since it supports reduced blanking, I tried creating a reduced blanking mode:

$ cvt -r 1680 1050
# 1680x1050 59.88 Hz (CVT 1.76MA-R) hsync: 64.67 kHz; pclk: 119.00 MHz
Modeline "1680x1050R"  119.00  1680 1728 1760 1840  1050 1053 1059 1080 +hsync
-vsync
$ xrandr --newmode 1680x1050R 119.00  1680 1728 1760 1840  1050 1053 1059 1080
+hsync -vsync
$ xrandr --addmode HDMI3 1680x1050R
$ xrandr --output HDMI3 --mode 1680x1050R

The new mode works without any glitching.

If I do the previous test, and while the screen is glitching do "xrandr
--output HDMI3 --mode 1680x1050R", the screen will immediately stop glitching.

So perhaps OS X is using a reduced blanking mode, or some other altered
timings, and that is why the glitching does not appear there.

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