[Intel-gfx] 3.0 (or SNA?) regression: failed to train DP, aborting

[Keith Packard]

On Sat, 23 Jul 2011 14:40:36 -0400, Andrew Lutomirski <luto at mit.edu> wrote:
> I have a Q67 (DQ67SW board) attached to a Dell U2711 via DP.  In
> previous kernels, the DP link has worked flawlessly.  I just booted
> 3.0-final and simultaneously enabled SNA, and now when my screen goes
> to sleep I don't get an image back until I power cycle the monitor.
> dmesg says:
> 
> [drm:intel_dp_complete_link_train] *ERROR* failed to train DP,
> aborting

Jesse put together a set of 7 display port patches around July 7 which
were merged just after 3.0-rc6. If you try 3.0-rc6 and find that it
works, you should be able to bisect that really quickly; there are only
13 patches post-rc6 in drivers/gpu/drm/i915:

$ git bisect start v3.0 v3.0-rc6 -- drivers/gpu/drm/i915

We tested this on as many machines as we could get our hands on, but
it's a combinatorial problem between the chipset and the monitor...

> I don't know whether this is a 3.0 regression or whether it's
> triggered by SNA, but something broke.

Yeah, as you noticed, this should have no effect. Please let us know
what you find.

-- 
keith.packard at intel.com
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