[RFC 0/4] drm/mipi-dbi: Support panel drivers

[Josef Luštický]

Yes, the onboard RAM is ili9341 feature.
I am able to drive the DisplayTech DT024CTFT panel in both modes.

I've just tested the DisplayTech DT024CTFT panel with your patchset
and it works fine with parallel RGB input mode:
compatible = "displaytech,dt024ctft", "ilitek,ili9341";
and with SPI input mode:
compatible = "mi,mi0283qt", "ilitek,ili9341";

However, there seems to be an issue when i use
compatible = "displaytech,dt024ctft", "ilitek,ili9341";
but no port property.
This is caused by calling dt024ctft_prepare in such case.

I would expected the driver to fallback to SPI input mode in such case.
In other words, the ili9341-based panels can be used in both modes,
but not all displays available
on the market provide breakout pins for the parallel RGB connection.

út 30. 7. 2019 v 16:08 odesílatel Noralf Trønnes <noralf at tronnes.org> napsal:
>
>
>
> Den 30.07.2019 08.40, skrev Josef Luštický:
> > Hi Noralf,
> > the patch series looks good, see comments in the patch emails.
> >
> > One question: is there a general mechanism to tell a driver not to use
> > parallel RGB even though
> > the display supports it and "port" is specified in the device-tree?
> >
>
> Not that I know of. It was just one difference that stood out which
> would make it easy to have the same panel driver support both DPI and
> DBI pixel mode.
>
> Since your panel has a ili9341 I assmue it has onboard RAM? So you
> should be able to drive your display in both modes I guess.
>
> Noralf.
>
> > Josef
> >
> > po 29. 7. 2019 v 21:55 odesílatel Noralf Trønnes <noralf at tronnes.org> napsal:
> >>
> >> Inspired by the thread[1] following the submission of a new ili9341
> >> panel driver[2], I set out to see if I could support panel drivers in
> >> drm_mipi_dbi.
> >>
> >> I have included the original driver, done some prep work on it, added
> >> panel support to drm_mipi_dbi and converted mi0283qt to this new panel
> >> driver.
> >>
> >> The big question is whether or not panel drivers should be allowed to
> >> turn themselves into full fledged DRM drivers.
> >>
> >> Noralf.
> >>
> >> [1]
> >> https://lists.freedesktop.org/archives/dri-devel/2019-July/228193.html
> >> [2] https://patchwork.freedesktop.org/patch/316528/
> >>
> >> Josef Lusticky (1):
> >>   drm/panel: Add Ilitek ILI9341 parallel RGB panel driver
> >>
> >> Noralf Trønnes (3):
> >>   drm/panel/ili9341: Rebase and some more
> >>   drm/mipi-dbi: Support command mode panel drivers
> >>   drm/panel/ili9341: Support mi0283qt
> >>
> >>  MAINTAINERS                                  |   6 +
> >>  drivers/gpu/drm/drm_mipi_dbi.c               | 110 +++++
> >>  drivers/gpu/drm/panel/Kconfig                |   9 +
> >>  drivers/gpu/drm/panel/Makefile               |   1 +
> >>  drivers/gpu/drm/panel/panel-ilitek-ili9341.c | 452 +++++++++++++++++++
> >>  include/drm/drm_mipi_dbi.h                   |   8 +
> >>  6 files changed, 586 insertions(+)
> >>  create mode 100644 drivers/gpu/drm/panel/panel-ilitek-ili9341.c
> >>
> >> --
> >> 2.20.1
> >>
> >