[Bug 89055] [SKL APL] 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 #61 from Matt Roper <matthew.d.roper at intel.com> ---
(In reply to Matt Roper from comment #60)
> (In reply to Oli from comment #59)
> > Not sure if this is related, but I saw the same OOPSs in my dmesg log,
> > though I assumed I apply this patch in order to get 4k output at 60 Hz.
> > 
> > Short background, I have a Dell XPS 13 9350 with an Intel Iris 540. See
> > `lspci -vvnn` here: http://ix.io/DEG
> > 
> > I applied the patch and started the new kernel with i915.enable_rc6=0, in
> > the hope that I could finally `xrandr --output DP1 --mode 3840x2160 --rate
> > 60`. Though, when I issue this, my screen goes blank with the following
> > error:
> > 
> [snip]
> > 
> > The whole dmesg is here: http://ix.io/DEH
> > 
> > Could someone give me a hint how to achieve 4k output with an refresh rate
> > of 60 Hz?
> > 
> > Thanks in advance.
> 
> The message you're getting now doesn't appear to be related to watermarks,
> so I don't think your problems are caused or fixed by my patch series
> (although the message you see in your log now may have been hidden amid all
> the noise that my patches have now removed).  Can you file a new bug for
> that so that your issue doesn't get lost in the mix here?

Actually, I take that back; I missed the cpu_fifo_underrun_irq_handler line at
the bottom.  That would imply some watermark issues, although I suspect they
may be a different watermark issue related to scaling.  I have another series
of patches I'll be posting after the one for this bugzilla lands, and I suspect
that series may solve your scaling-related watermark problem.

Either way, please open a new bug report so we can track it separately from the
WARN_ON(!wm_changed) stuff going on here.

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