[Bug 90128] Big monitor has blank display (HDMI or DVI) in any kernel since and including 3.13 (despite earlier fixes)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90128

--- Comment #2 from philipmorant at gmail.com ---
I tested up to kernel 3.16.  The recent ubuntu kernel update
(3.16.0.37.29) also broke my monitor and I had to reapply my patch.

As for why the bugfix that introduced the respect_dvi_limit variable
(I think it was 72961 but am not sure) didn't work for me, I think it
might be like this: there's two paths through hdmi_portclock_limit(),
one of which has respect_dvi_limit set to false, to enable the case
where the mode is being requested interactively by an xrandr user.
But the other path has respect_dvi_limit set to true, and contrary to
the expectations of the people who introduced respect_dvi_limit that
path *is* exercised when specifying modes interactively via xrandr.
I'm not in a position to say for sure, but that's what it looks like.

I've always been able on all kernels to add the right mode using
xrandr, and xrandr seems happy and reports that the display is set to
2560x1440x60 and is using it ... but there's no picture on the
monitor.
$  xrandr
...snip...
HDMI1 connected 2560x1440+1920+0 (normal left inverted right x axis y
axis) 597mm x 336mm
   2560x1440      60.0*+

I'm guessing that the monitor only works with a refresh rate of 60Hz,
which would account for why I get no picture at the in-spec refresh
rate 30Hz.

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