On Wed, Apr 03, 2019 at 11:37:21AM -0700, Manasi Navare wrote:
> On Wed, Apr 03, 2019 at 03:14:51PM +0300, Ville Syrjälä wrote:
> > On Tue, Apr 02, 2019 at 02:52:34PM -0700, Manasi Navare wrote:
> > > For certain eDP 1.4 panels, we need to use max lane count for the
> > > link training to succeed.
> > >
> > > This patch adds a EDID quirk for such eDP panels using
> > > their vendor ID and product ID to force using max lane count in the
> > > driver.
> >
> > Rather than opening the quirk can of worms I think we should consider
> > changing the retry loop to do something more sensible than what it's
> > doing now. The current behaviour of "start at optimal settings (which
> > can be either min lanes or min rate), and then reduce lanes/rate until
> > stuff works" overlooks several possible combinations. One possible
> > approach could be to start the retry loop with max lanes + max rate
> > after the optimal settings have failed. It probably won't give you
> > the best power consumption, but at least you get a picture on the
> > screen if even a single lane count + rate combo works.
> >
>
> So you are saying that for eDP only we should modify the retry function to
> retry with max lanes and max rate so what we used to do earlier with < eDP
> 1.4?
>
> Hmm I could try doing that, the only concern I have there is that certain eDP
> panels just need a retry at same parameters to work so for such panels
> where the lower values of link rate/lane count work with just an extra retry
> we would still be using max link rate /lane count now with this change.
If the panels are borked then I wouln't worry about it as long a picture
appaears on the screen. And if the extra training cycle is because of
some bug in our code then we should figure it out what that bug is.
>
> Or are you suggesting doing the retry with same params for edp < 1.4 and for
> all
> edp 1.4 , we retry with , max link rate lane ocunt?
retrain_fail()
{
if (!use_max_params) {
use_max_params = true;
rate = max;
lanes = max;
} else {
reduce rate/lanes as usual
}
}
compute_config()
{
if (use_max_params) {
limits.min = limits.max;
}
...
}
or something like that.
--
Ville Syrjälä
Intel
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