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<b><a class="bz_bug_link
bz_status_ASSIGNED "
title="ASSIGNED - [IVB/HSW] 23.976Hz & 24Hz modes broken on dual-display with recent (4.0.x) kernels"
href="https://bugs.freedesktop.org/show_bug.cgi?id=91434#c35">Comment # 35</a>
on <a class="bz_bug_link
bz_status_ASSIGNED "
title="ASSIGNED - [IVB/HSW] 23.976Hz & 24Hz modes broken on dual-display with recent (4.0.x) kernels"
href="https://bugs.freedesktop.org/show_bug.cgi?id=91434">bug 91434</a>
from <span class="vcard"><a class="email" href="mailto:ville.syrjala@linux.intel.com" title="Ville Syrjala <ville.syrjala@linux.intel.com>"> <span class="fn">Ville Syrjala</span></a>
</span></b>
<pre>(In reply to Martin Andersen from <a href="show_bug.cgi?id=91434#c34">comment #34</a>)
<span class="quote">> There is no DP-HDMI dongle involved. The output is fed directly from a
> MacBook Retina system via full-size/regular HDMI cable. (Yes, I've also
> noticed it says DP.)</span >
That just means the DP++ chip is likely soldered onto the motherboard. It's
definitely somewhere because it answers when we talk to it.
<span class="quote">>
> However; the exact same setup works 100% correctly with older kernels, as
> outlined earlier in the ticket. By 100% i mean: never any picture dropouts,
> never any dots (which only were seen with this most recent kernel) or other
> graphical glitches.</span >
That's probably because older kernels only did 8bpc, whereas newer ones do
12bpc whenever possible.
<span class="quote">> I have three other sources hooked up to this projector, and none have
> issues.</span >
Can you tell whether any of them do 12bpc HDMI output, or just 8bpc?
<span class="quote">> The same behaviour is seen when hooked up directly to either of the
> projector's two HDMI ports - with another cable - as well. So I believe
> 'cabling issues' can be ruled out.</span >
The cables aren't unusually long are they?
It's definitely possible that the signal degradation happens either in the
source of sink side. I could almost excuse the source side for not being tested
to handle 12bpc iff Apple's own driver always uses 8bpc and they didn't expect
anyone to install another OS on the thing. If the problem is in the projector
then I think it's less excusable, and they should have tested to make sure the
device works with the maximum TMDS clock it's advertising to the source.</pre>
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