[Bug 82102] 4k monitor edid rejected: EDID timing clock 297.00 exceeds claimed max 115MHz, fixing

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=82102

--- Comment #11 from Roland Scheidegger <sroland at vmware.com> ---
(In reply to comment #9)
> (In reply to comment #8)
> > (In reply to comment #7)
> > > (In reply to comment #6)
> > > > You GPU does not support 4k over HDMI.
> > > The specs at AMD claim this GPU does HDMI 1.4a 2 lanes of 340 Mhz dot clock
> > > each for a total of 640 Mhz.   Even if only one lane is populated on this
> > > card, that should still be 340 Mhz.   The modeline only asks for 297 Mhz.
> > Where to they claim that? I think you've been successfully fooled by the
> > HDMI forum, which allows anyone to implement some boring subfeatures noone
> > is interested in and leave out the only thing important, namely higher
> > frequencies, and still claiming newer standards (1.4 in this case)
> > compliance regardless (for receiver devices which don't have such a high
> > resolution this actually even makes sense).
> 
> The spec sheet at the URL you quote below mentions HDMI 1.4a.   Although I
> can see how they might be skirting the truth about HDMI 1.4 compliance.
1.4a only added some 3d formats (frame packing), but only with resolutions
which you can do with "old" frequencies (1080p24 x2 and similar). hdmi 1.3 (!)
was actually the new version which introduced the higher frequencies, though I
think devices claiming to only be hdmi 1.3 compliant actually supporting the
higher frequencies were very, very rare (if they even exist). It is possible
supporting these was mandatory with 1.4b (cause it introduced 1080p60 x2) but I
wouldn't bet on it neither.
Similarly, there's now "HDMI 2.0" devices out there which only support 4k with
30Hz and not 60Hz (or more specifically, 340Mhz frequency instead of 600Mhz).
All the same old story.

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