[Bug 104918] [SKL] enable_psr=1 on 4.15 causes rapid hangs

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=104918

--- Comment #2 from Andy Lutomirski <luto at kernel.org> ---
Created attachment 137145
  --> https://bugs.freedesktop.org/attachment.cgi?id=137145&action=edit
Non-working fix attempt

I wrote up the attached patch.  It makes the sequence of flushes and PSR
activations make a lot more sense to me, although it's rather hacky.  It
doesn't fix the hang, though.  It might fix the latency issue I was seeing,
though, but it's very hard to tell when the system hangs so quickly.


(Part of the hackiness is that I'm not sure that schedule_delayed_work()
actually promises to wait as long as it's asked to.  I suspect that a better
solution would be to use timers or even to use the vblank interrupt to trigger
PSR activation.  mod_timer() is actually intended for this type of usage.)

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