linux-kernel - Re: [v4 2/3] drm/panel: ili9882t: Avoid blurred screen from fast sleep

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Message-ID: <CAD=FV=UV_yX=wBDMY1LhENfMYSbcZ=8xiCnQ6P3NXWdCHbn+zw@mail.gmail.com>
Date:   Thu, 19 Oct 2023 14:50:12 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Cong Yang <yangcong5@...qin.corp-partner.google.com>
Cc:     sam@...nborg.org, neil.armstrong@...aro.org, daniel@...ll.ch,
        hsinyi@...gle.com, linus.walleij@...aro.org, swboyd@...omium.org,
        airlied@...il.com, catalin.marinas@....com, will@...nel.org,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [v4 2/3] drm/panel: ili9882t: Avoid blurred screen from fast sleep

Hi,

On Fri, Oct 13, 2023 at 2:43 PM Doug Anderson <dianders@...gle.com> wrote:
>
> Hi,
>
> On Fri, Oct 13, 2023 at 2:19 AM Cong Yang
> <yangcong5@...qin.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.. 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@...qin.corp-partner.google.com>
> > ---
> >  drivers/gpu/drm/panel/panel-ilitek-ili9882t.c | 22 ++++++++++++++++++-
> >  1 file changed, 21 insertions(+), 1 deletion(-)
>
> As talked about in response to the previous version [1], we can work
> to see if we can improve the sequencing. However, for now this seems
> fine.
>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>
>
> [1] https://lore.kernel.org/r/CAD=FV=W_LT9mPYKjaKP3OvUDeNpsZxkhVN9NP_hQ+Es6Fe3dVw@mail.gmail.com

Pushed to drm-misc-next:

5820a1932ce8 drm/panel: ili9882t: Avoid blurred screen from fast sleep