Re: [v1 2/2] drm/panel: ili9882t: Avoid blurred screen from fast sleep

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Hi,

On Wed, Oct 11, 2023 at 3:11 AM Doug Anderson <dianders@xxxxxxxxxx> wrote:
>
> Hi,
>
> On Tue, Oct 10, 2023 at 4:36 AM cong yang
> <yangcong5@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > Hi,
> >
> > On Tue, Oct 10, 2023 at 4:44 AM Doug Anderson <dianders@xxxxxxxxxx> wrote:
> > >
> > > Hi,
> > >
> > > On Fri, Oct 6, 2023 at 11:07 PM Cong Yang
> > > <yangcong5@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > > >
> > > > At present, we have found that there may be a problem of blurred
> > > > screen during fast sleep/resume. The direct cause of the blurred
> > > > screen is that the IC does not receive 0x28/0x10. Because of the
> > > > particularity of the IC, before the panel enters sleep hid must
> > > > stop scanning, i2c_hid_core_suspend before ili9882t_disable.
> > > > This doesn't look very spec-compliant.
> > >
> > > Presumably you could be more spec compliant if we used
> > > "panel_follower" in this case? Would that be a better solution?
> >
> > In the "panel_follower" solution, the phenomenon is the same.
> > The current order is
> > ili9882t_disable=>i2c_hid_core_suspend=>elan_i2c_hid_power_down=>ili9882t_unprepare,
> > ili9882t need touchpanel stop scanning,i2c_hid_core_suspend before
> > ili9882t_disable.
>
> Ugh, that's unfortunate. Though is there a reason why you couldn't
> just move the `ili9882t_enter_sleep_mode()` to `ili9882t_unprepare()`?
> That seems like it should be OK and even perhaps makes it more
> symmetric with thue enable?

Thank you for your suggestion. If the timing is met and there is no problem,
I will implement it in V3.

>
>
> > > > @@ -507,7 +526,7 @@ static int ili9882t_prepare(struct drm_panel *panel)
> > > >         gpiod_set_value(ili->enable_gpio, 1);
> > > >         usleep_range(1000, 2000);
> > > >         gpiod_set_value(ili->enable_gpio, 0);
> > > > -       usleep_range(1000, 2000);
> > > > +       usleep_range(40000, 50000);
> > >
> > > nit: use 40000, 41000 instead of 40000, 50000. Linux almost always
> > > uses the longer delay, so that'll save ~9 ms. The only reason for the
> > > range is to optimize kernel wakeups which is really not a concern
> > > here.
> >
> > We need 50ms delay to meet the requirement.
>
> I'll respond to your v2, but if you need 50 ms then your current delay is wrong.
>
>
> -Doug





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