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

[Doug Anderson]

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?


> > > @@ -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