[Intel-gfx] [PATCH] drm/i915/dp: Reset link params on connector disconnect

[Imre Deak]

On Thu, Jun 04, 2020 at 12:40:20PM -0700, Manasi Navare wrote:
> On Thu, Jun 04, 2020 at 10:23:40PM +0300, Imre Deak wrote:
> > On Thu, Jun 04, 2020 at 10:08:58PM +0300, Imre Deak wrote:
> > > On Thu, Jun 04, 2020 at 10:01:40PM +0300, Ville Syrjälä wrote:
> > > > [...]
> > > > > > Then we get this hpd, in this case if we dont reset the param to max values, prev triggered modeset continues
> > > > > > with fallback values but since connector probe doesnt happen again through IGT, it tries the same mode
> > > > > > with fallback values and return encoder config failure.
> > > > > 
> > > > > If the link training failed then clearly the sink didn't like us anymore
> > > > > anyway. So feels like resetting these here is just shifting some race
> > > > > window around a bit, but it could still fail if the sink still doesn't
> > > > > like us.
> > > > > 
> > > > > Would be good if someone was able to figure out why the sink goes bad in
> > > > > the first place.
> > > > 
> > > > Oh, and don't we now have Imre's "weird hpd happened in the middle of
> > > > the test, don't trust the results" thing in igt?
> > > 
> > > An LG and IIyama monitor this happens on disconnect and reconnect after
> > > waking from an idle state when modesetting them, not sure if it's the
> > > same case.
> > 
> > Manasi, could you try if a modeset on the monitor after it has been
> > disabled for a while always results in a long HPD pulse a few seconds
> > after the modeset? If so does this also happen when you just modeset in
> > a sequence from one mode to the other not letting the monitor idle? The
> > same monitor should be also tested then with the above sequences on
> > older platforms if it behaves the same on those too.
> >
> 
> This test has been passing on older ICL platforms. But on TGL we do
> see these AUX E timeouts once in a while which recover on their own
> for the next modeset. Any idea why these spurious AUX timeouts and how
> I can possibly rootcause why these timeouts are seen only with AUX E?

If the monitor is in a disconnected state as you described, then AUX
will fail too. So you need to root cause why the monitor gets
disconnected. One possibility for that is what I described above. You
can't really make a conclusion on a test passing on ICL and not on TGL,
the timing can be different. You'd need to check if a disconnect happens
due to long HPD pulse when using the same monitor with the sequences I
described above, both on TGL and then also on ICL.

> 
> Manasi
>  
> > > 
> > > --Imre
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