[Bug 109477] [regression, bisected] [i915] setting initial watermarks on gen 7 IVYBRIDGE causes blank lines on monitor

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=109477

--- Comment #10 from Andrea <andreatclist at gmail.com> ---
(In reply to Andrea from comment #9)
> (In reply to Ville Syrjala from comment #8)
> > (In reply to Andrea from comment #7)
> > > (In reply to Ville Syrjala from comment #6)
> > > > All the numbers look very much correct :/
...
> > > > And finally LP1:
> > > > # echo '12 0 0 0' > /sys/kernel/debug/dri/0/i915_pri_wm_latency
> > > > # echo '12 0 0 0' > /sys/kernel/debug/dri/0/i915_cur_wm_latency
> > > > $ xset dpms force off ; xset dpms force on
> > > > Still corrupted?
> > > 
> > > No, the corruption is gone. Switching windows, desktops, focus etc seems to
> > > work fine. And it doesn't re-appear after > 10 mins.
> > 
> > Hmm. That machine seems very broken when even LP1 doesn't work.
> 
> Umm, I guess there might be a misunderstanding: after setting LP1 with the
> values you suggested, the corruption is gone and everything seems to be OK
> as before the regression.
> 
> Anyway, I'll also try the BIOS update and post the results (thanks for the
> pointer, I'll check).

JFTR, I've updated to "DMI: LENOVO 20AA0016GE/20AA0016GE, BIOS GHET41WW (1.26 )
11/21/2018", same results:
- the monitor starts corrupted
- setting echo '12 0 0 0' > /sys/kernel/debug/dri/0/i915_pri_wm_latency ...
"fixes" the issue.

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