Re: [PATCH RFC 03/10] drm/panel: Add LGD panel driver for Sony Xperia XZ3

[Dmitry Baryshkov]

On 30/05/2023 01:37, Marijn Suijten wrote:
> On 2023-05-30 01:18:40, Dmitry Baryshkov wrote:
> <snip>
> > > > > > > +    ret = mipi_dsi_dcs_set_display_on(dsi);
> > > > > > > +    if (ret < 0) {
> > > > > > > +        dev_err(dev, "Failed to turn display on: %d\n", ret);
> > > > > > > +        return ret;
> > > > > > > +    }
> > > > > >
> > > > > > My usual question: should the mipi_dsi_dcs_exit_sleep_mode() / mipi_dsi_dcs_set_display_on() be moved from prepare() to enable() part?
> > > > >
> > > > >
> > > > > No, prepare is called before the video stream is started and when display is still in LPM mode and the mode hasn't been set.
> > > >
> > > > Yes, that's my point. Shouldn't we enable the panel _after_ starting the stream?
> > >
> > > I have never investigated what it takes to split these functions, but
> > > some of these panels do show some corruption at startup which may be
> > > circumvented by powering the panel on after starting the video stream?
> > >
> > > I'm just not sure where to make the split: downstream does describe a
> > > qcom,mdss-dsi-on-command and qcom,mdss-dsi-post-panel-on-command, where
> > > the latter only contains set_display_on() (not exit_sleep_mode()).
> > > It is documented like:
> > >
> > >       same as "qcom,mdss-dsi-on-command" except commands are sent after
> > >       displaying an image."
> > >
> > > So this seems like the right way to split them up, I'll test this out on
> > > all submitted panel drivers.
> >
> > Interesting enough, Neil suggested that sending all the commands during
> > pre_enable() is the correct sequence (especially for VIDEO mode panels),
> > since not all DSI hosts can send commands after switching to the VIDEO mode.
>
> Note that all these panels and Driver-ICs are command-mode, and/or
> programmed to run in command-mode, so there shouldn't be any notion of a
> VIDEO stream (any command-mode frame is just an "arbitrary command" as
> far as I understood).

Yes, from the data stream point of view. I was talking about the DSI 
host being able to send arbitrary commands or not after enabling the 
video/cmd stream.

> - Marijn

--
With best wishes
Dmitry