[Bug 101245] Haswell ULT max. resolution regression in KMS [HSW] [i915]

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101245

--- Comment #16 from Ville Syrjala <ville.syrjala at linux.intel.com> ---
(In reply to Michael Mounteney from comment #15)
> So everything works as intended but the monitor no longer switches to the
> highest resolution.
> 
> It seems that the problem is that the EDID is reporting single-link, which
> is relevant to DVI-D, but my connection is HDMI.  Doesn't it make sense to
> ignore any single-link/dual-link information with an HDMI connection? 
> Possibly with CONFIG_HDMI_IGNORE_LINK_ARITY ?
> 
> If you aren't prepared to do this, could you at least supply an indication
> of where to hack the source;  otherwise I am stuck on kernel 4.7.4 for ever,
> or for at least as I continue to use Linux.

The monitor is basically telling us that you need dual link DVI to reach the
highest resolutions, but HDMI is always single link (and Intel hardware can't
do dual link DVI anyway) so we high resolution modes get filtered out.

One option to overcome this would be to hack the EDID to remove/increase the
TMDS clock limit (and fix up the checksum appropriately), and then use the
firmware EDID load mechanism to override the EDID with the hacked version. That
wouldn't require any code changes, and wouldn't require the use of custom
modelines.

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