[Bug 71267] sna: (Haswell) X-server freezes when enabling DP at docking station

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=71267

--- Comment #31 from Todd Previte <tprevite at gmail.com> ---
Jani and I had a conversation about this not-so-very-long ago. Unfortunately,
the spec is rather vague on the details of AUX_DEFERs. There's a little bit
more information in there for I2C-over-AUX behavior, but nothing directly about
native AUX_DEFERs as far as retry timeouts go. Essentially the spec just says
"the source device can try again later" and leaves it at that. There's also an
instance in the spec that says "assumes the Source repeats request immediately
following a DP Sink AUX Defer response". Nothing like consistency...

That said, I would think that up to 300us would be a safe value for a retry
timeout. That should be fine for isolated DEFERs or even a short series of
them. However, lots of defers with a timeout value like this can stretch AUX
operations out beyond specified specified time limits (10ms for link training
for instance), so that's something to keep in mind.
-T

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