[v3 2/3] drm/panel: ili9882t: Avoid blurred screen from fast sleep

[cong yang]

Hi,

On Thu, Oct 12, 2023 at 11:15 PM Doug Anderson <dianders at google.com> wrote:
>
> Hi,
>
> On Thu, Oct 12, 2023 at 5:10 AM Cong Yang
> <yangcong5 at huaqin.corp-partner.google.com> 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, as i2c_hid_core_suspend before ili9882t_disable.
> > If move the ili9882t_enter_sleep_mode function to ili9882t_unprepare,
> > touch reset will pull low before panel entersleep, which does not meet
> > the timing requirements..
>
> The above makes me believe that the reset GPIO should be moved out of
> the input driver and into the panel driver. I could just imagine that
> the kernel might have some reason it wants to suspend the i2c hid
> device. If that causes the panel to suddenly start failing then that
> would be bad... I think we should fix this.

Thanks, I will confirm with ilitek in further analysis and use "move
the ili9882t_enter_sleep_mode
function to ili9882t_unprepare".  Is the test failure really because
the touch reset timing
does not match? There is also a separate reset GPIO on the panel.
Shouldn't touch reset not
affect the panel?

If we find a better solution I will continue upstream,。 So is it
possible to apply this plan now?

>
>
> > So in order to solve this problem, the IC
> > can handle it through the exception mechanism when it cannot receive
> > 0x28/0x10 command. Handling exceptions requires a reset 50ms delay.
> > Refer to vendor detailed analysis [1].
> >
> > Ilitek vendor also suggested switching the page before entering sleep to
> > avoid panel IC not receiving 0x28/0x10 command.
> >
> > Note: 0x28 is display off, 0x10 is sleep in.
> >
> > [1]: https://github.com/ILITEK-LoganLin/Document/tree/main/ILITEK_Power_Sequence
> >
> > Signed-off-by: Cong Yang <yangcong5 at huaqin.corp-partner.google.com>
> > ---
> >  drivers/gpu/drm/panel/panel-ilitek-ili9882t.c | 22 ++++++++++++++++++-
> >  1 file changed, 21 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9882t.c b/drivers/gpu/drm/panel/panel-ilitek-ili9882t.c
> > index 93a40c2f1483..54ff1efb94aa 100644
> > --- a/drivers/gpu/drm/panel/panel-ilitek-ili9882t.c
> > +++ b/drivers/gpu/drm/panel/panel-ilitek-ili9882t.c
> > @@ -463,6 +463,24 @@ static int ili9882t_init_dcs_cmd(struct ili9882t *ili)
> >         return 0;
> >  }
> >
> > +static int ili9882t_switch_page(struct mipi_dsi_device *dsi, u8 page)
> > +{
> > +       int ret;
> > +       const struct panel_init_cmd cmd = _INIT_SWITCH_PAGE_CMD(page);
> > +
> > +       ret = mipi_dsi_dcs_write(dsi, cmd.data[0],
> > +                                cmd.len <= 1 ? NULL :
> > +                                &cmd.data[1],
> > +                                cmd.len - 1);
> > +       if (ret) {
> > +               dev_err(&dsi->dev,
> > +                       "error switching panel controller page (%d)\n", ret);
> > +               return ret;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> >  static int ili9882t_enter_sleep_mode(struct ili9882t *ili)
> >  {
> >         struct mipi_dsi_device *dsi = ili->dsi;
> > @@ -484,8 +502,10 @@ static int ili9882t_enter_sleep_mode(struct ili9882t *ili)
> >  static int ili9882t_disable(struct drm_panel *panel)
> >  {
> >         struct ili9882t *ili = to_ili9882t(panel);
> > +       struct mipi_dsi_device *dsi = ili->dsi;
> >         int ret;
> >
> > +       ili9882t_switch_page(dsi, 0x00);
> >         ret = ili9882t_enter_sleep_mode(ili);
> >         if (ret < 0) {
> >                 dev_err(panel->dev, "failed to set panel off: %d\n", ret);
> > @@ -546,7 +566,7 @@ 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(50000, 51000);
>
> From my previous response, I think the above is better as msleep(50).

Sorry. Will be corrected in V4.