[PATCH v1 1/1] board: acer: picasso: add Acer Iconia Tab A500 support

[Svyatoslav Ryhel]

пн, 17 лют. 2025 р. о 18:51 Quentin Schulz <quentin.schulz at cherry.de> пише:
>
> Hi Svyatoslav,
>
> On 2/16/25 7:16 PM, Svyatoslav Ryhel wrote:
> > The Acer Iconia A500 is a tablet computer designed, developed and
> > marketed by Acer Inc. It is powered by 1 GHz Nvidia Tegra 2 processor
> > and 1GB DDR2 RAM. The A500 is sold with 64 GB, although both 16 GB
> > and 32 GB models are available.
> >
> > Signed-off-by: Svyatoslav Ryhel <clamor95 at gmail.com>
> > ---
> >   arch/arm/dts/Makefile                      |   1 +
> >   arch/arm/dts/tegra20-acer-a500-picasso.dts | 508 +++++++++++++++++++++
> >   arch/arm/mach-tegra/tegra20/Kconfig        |   5 +
> >   board/acer/picasso/Kconfig                 |  12 +
> >   board/acer/picasso/MAINTAINERS             |   7 +
> >   board/acer/picasso/Makefile                |   9 +
> >   board/acer/picasso/picasso.c               |  57 +++
> >   board/acer/picasso/picasso.env             |  18 +
> >   configs/picasso_defconfig                  |  83 ++++
> >   doc/board/acer/index.rst                   |   9 +
> >   doc/board/acer/picasso.rst                 | 125 +++++
> >   doc/board/index.rst                        |   1 +
> >   include/configs/picasso.h                  |  23 +
> >   13 files changed, 858 insertions(+)
> >   create mode 100644 arch/arm/dts/tegra20-acer-a500-picasso.dts
> >   create mode 100644 board/acer/picasso/Kconfig
> >   create mode 100644 board/acer/picasso/MAINTAINERS
> >   create mode 100644 board/acer/picasso/Makefile
> >   create mode 100644 board/acer/picasso/picasso.c
> >   create mode 100644 board/acer/picasso/picasso.env
> >   create mode 100644 configs/picasso_defconfig
> >   create mode 100644 doc/board/acer/index.rst
> >   create mode 100644 doc/board/acer/picasso.rst
> >   create mode 100644 include/configs/picasso.h
> >
> > diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
> > index 0bf3697bdbe..acea0cc2ec1 100644
> > --- a/arch/arm/dts/Makefile
> > +++ b/arch/arm/dts/Makefile
> > @@ -84,6 +84,7 @@ dtb-$(CONFIG_ARCH_MESON) += \
> >       meson-a1-ad401.dtb
> >
> >   dtb-$(CONFIG_ARCH_TEGRA) += \
> > +     tegra20-acer-a500-picasso.dtb \
> >       tegra20-asus-sl101.dtb \
> >       tegra20-asus-tf101.dtb \
> >       tegra20-asus-tf101g.dtb \
> > diff --git a/arch/arm/dts/tegra20-acer-a500-picasso.dts b/arch/arm/dts/tegra20-acer-a500-picasso.dts
> > new file mode 100644
> > index 00000000000..0c301483180
> > --- /dev/null
> > +++ b/arch/arm/dts/tegra20-acer-a500-picasso.dts
>
> Small drive-by comment.
>
> This is quite different from the Device Tree in the Linux kernel tree,
> and it hasn't been changed a lot in the last few years.
>
> 1) Is there any reason for not sync'ing with upstream Linux kernel
> instead of having our own Device Tree?
> 2) Do you think it'd be possible to use OF_UPSTREAM instead which would
> make it possible to use the device tree from the Linux kernel (it is
> available in dts/upstream/src/arm/nvidia/tegra20-acer-a500-picasso.dts)?
> I don't think it's a straightforward thing to do but haven't do it
> myself, so no clue what's required and the amount of effort to put into
> it. The benefit is that fixes to the DT will eventually make it to
> U-Boot as well and we hopefully lower the maintenance burden on U-Boot
> contributors/maintainers.
>
> Cheers,
> Quentin

Short answers yes and yes.

Long answer:
1. Using Linux Kernel device tree will result in at least total
failure of entire video subsystem since Linux gpu/drm changed
extremely quick. All devices I have submitted, including A500 heavily
relay on video output to be operated correctly (being a production
devices there is no exposed uart or any other output, besides the
panel). This is only at the first glance, there may be more under the
surface. At the same time, even if we switch to Linux device trees,
this will not remove need of *-u-boot.dts to adjust Linux tree to
U-Boot reality.

2. It is possible and it is even one of my current priorities.
Hopefully, by the fall I will be able to configure existing frameworks
and drivers to comply existing Linux trees. A small example, atm
U-Boot has no helpers to parse of_graph bindings, which are heavily
used by Linux to link video devices (that is expected since there is
not so much devices are using video output so no one bothered). This
makes most Linux bindings of video devices useless for U-Boot. Don't
assume that each or nearly each framework has such flows, they are
uncommon, but nonetheless they occur and destroy full picture.