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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - [Regression]Multiple monitors via DP TB dock detection/resolution/layout failure after Skylake->Coffeelake upgrade"
href="https://bugs.freedesktop.org/show_bug.cgi?id=111179#c11">Comment # 11</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - [Regression]Multiple monitors via DP TB dock detection/resolution/layout failure after Skylake->Coffeelake upgrade"
href="https://bugs.freedesktop.org/show_bug.cgi?id=111179">bug 111179</a>
from <span class="vcard"><a class="email" href="mailto:arcadiy@ivanov.biz" title="Arcadiy Ivanov <arcadiy@ivanov.biz>"> <span class="fn">Arcadiy Ivanov</span></a>
</span></b>
<pre>Thanks for looking at this.
Both Dell Precision 7510 (SKL) and Dell Precision 5540 (CFL) have the same TB
capabilities, TB3 ***HBR2***. It's true, with HBR2 they don't support
2x4k@60Hz(**), but the point of filing this bug was somewhat different - there
was a change in behavior in monitor detection and resolution/refresh rate
setting.
SKL was supporting 2x4k with auto-detection, which, given hardware limitations,
means that it was settling on 2x4k@30Hz mode all by itself. When an upgrade was
made to CFL, this auto-detection stopped working properly - as you can see it
tried to configure 2x4K@60Hz and failed, without fallback to 2x4K@30Hz.
The change in behavior cannot be blamed on changes in Xorg, xrandr etc - the
entire SSD was moved. Dock is similarly blameless - it was the same dock. The
only change was laptop hardware. Given that monitors could be detected and EDID
was read the expected fallback should've been onto the 2x4K@30Hz on CFL same as
on SKL. It wasn't.
All firmware is up-to-date.
=====
** there is a way with WD19TB for 2x4k@60Hz with DP pass-through, but this
wasn't the setup for this bug</pre>
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