Re: [PATCH] drm/bridge: ps8640: Add double reset T4 and T5 to power-on sequence

[Doug Anderson]

Hi,

On Thu, Aug 18, 2022 at 8:03 AM Doug Anderson <dianders@xxxxxxxxxxxx> wrote:
>
> Hi,
>
> On Wed, Aug 17, 2022 at 8:22 PM Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote:
> >
> > On Thu, Aug 18, 2022 at 11:19 AM Rock Chiu
> > <rock.chiu@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > >
> > > How does T4/T5  impact the real case? We talked previously the T4/T5
> > > shouldn't cause user impact.
> > > Do we have testing data from ODM?
> > >
> > Please leave comments below the previous comment's headline.
> >
> > I'm confused. The reason I upstreamed this patch is because this is in
> > your application note and you asked us to help upstream it. Now do you
> > mean that we don't need T4 and T5?
>
> I think Rock is asking what problems the extra delay is causing. In
> other words: why do we care about keeping these delays short?
>
> The answer is that it affects boot speed and also resume speed of
> devices. Adding these two delays here means that there's an extra 100
> ms before the user can see something on the screen. That may not seem
> like a lot, but those kinds of delays add up quickly. At least on
> Chromebooks, booting quickly is always a big goal.

While I'm not very happy with this change and I don't really
understand why these delays need to be so long, if folks are really
certain that we need them and can't make them shorter then I guess we
can land it. I'll wait a few more days in case anyone wants to chime
in with their thoughts.

-Doug