[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 #9 from Andrea <andreatclist at gmail.com> ---
(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 :/
> > > 
> > > Does the corruption go away if you start X (or whatever) that enables the
> > > hardware cursor? The watermark dumps at least seemed to be w/o the cursor.
> > 
> > The corruption is present since boot-time, and stays there when the X
> > starts. Sometimes it disappears (e.g., in response to a window/desktop
> > switch), but in a non-deterministic way and the corruption comes back later.
> > 
> > > I see the BIOS is pretty old. Can you try to update it?
> > 
> > I will try in the next days, but from a first look it seems all updates
> > require Windows (which I've not on this system).
> 
> Dunno if this is the right one, but some T431s seems to have ISOs available
> for BIOS update:
> https://download.lenovo.com/pccbbs/mobiles/ghuj20us.iso
> 
> > 
> > > Let's also try to figure out which watermark level is the problem.
> > > Please do these tests with drm-tip because it might not work with an older
> > > kernel.
> > > 
> > > First let's rule out LP3:
> > > # echo '12 4 16 0' > /sys/kernel/debug/dri/0/i915_pri_wm_latency
> > > # echo '12 4 16 0' > /sys/kernel/debug/dri/0/i915_cur_wm_latency
> > > $ xset dpms force off ; xset dpms force on
> > > Still corrupted?
> > 
> > Yes
> > 
> > > Then LP2:
> > > # echo '12 4 0 0' > /sys/kernel/debug/dri/0/i915_pri_wm_latency
> > > # echo '12 4 0 0' > /sys/kernel/debug/dri/0/i915_cur_wm_latency
> > > $ xset dpms force off ; xset dpms force on
> > > Still corrupted?
> > 
> > Yes
> > 
> > > 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).

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