[Bug 72961] [hdmi to dual-link dvi regression] Patch to hdmi_portclock_limit disables resolutions that worked with the 3.13.6 kernel

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=72961

--- Comment #4 from Ville Syrjala <ville.syrjala at linux.intel.com> ---
Created attachment 130731
  --> https://bugzilla.kernel.org/attachment.cgi?id=130731&action=edit
[PATCH] drm/i915: Allow user modes to exceed DVI 165MHz limit

Based on what the cable looks like, I think it's just a plain old passive
single link DVI <-> HDMI cable. So it looks like your monitor accepts out of
spec frequencies on the DVI connector. Probably it's just a HDMI input w/ a DVI
connector. But the monitor apparently doesn't report back the HDMI VSDB EDID
block so the source can't identify it as a HDMI monitor, which means the driver
can't know that the monitor will accept HDMI signals.

In this case we just filter out the high resolution modes, so you still get a
picture on the screen, but if we were to revert the patch then people with
monitors which don't accept out of spec DVI signals would get no picture at
all. So we get to pick the option where everyone gets at least some kind of
picture.

But the patch does seem to be a bit too strict. We should probably still allow
you to manually add the mode w/ xrandr. In that case you're basically telling
the driver that you know what you're doing. This patch attempts to fix that.
Let me know if it works.

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