[Bug 89055] [SKL ] WARN_ON(!wm_changed) hit in the WM code with multiple pipes enabled

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89055

--- Comment #35 from Matt Roper <matthew.d.roper at intel.com> ---
(In reply to Prasad H L Bhat from comment #34)
> I get the same error sometimes on my T460 laptop with Intel HD Graphics 520.
> When it occurs, it freezes the laptop completely (display turns off, no
> virtual terminals work, audio buffer keeps looping if present when freezing).

I don't think the message is the cause of your hang.  The message here is a
harmless warning that we're needlessly re-calculating something we shouldn't
be.  That's something we shouldn't be doing (and I'm in the process of fixing),
but it won't actually cause any harm or trigger a system hang.

The WARN() here will often show up any time a modeset operation happens while
you're using multiple displays.  It sounds like something else is going wrong
for you during that modeset which does cause a hang and this message just
happens to be the last thing you wind up seeing.

Could you please open a new bugzilla describing the details of your setup and
any actions that trigger the hang for you?  It's unlikely that fixing this
message here will fix your hang, so we'll want to investigate your report
separately.

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