Re: [PATCH] arm64: dts: rockchip: Split rk3399-roc-pc for with and without mezzanine board.

[Jagan Teki <jagan@amarulasolutions.com>]

Hi Markus,

On Mon, Nov 18, 2019 at 5:27 PM Markus Reichl <m.reichl@fivetechno.de> wrote:
>
> Hi Jagan,
>
> Am 18.11.19 um 12:44 schrieb Jagan Teki:
> > On Mon, Nov 4, 2019 at 5:42 PM Heiko Stübner <heiko@sntech.de> wrote:
> >>
> >> Hi Markus,
> >>
> >> Am Freitag, 1. November 2019, 17:54:23 CET schrieb Markus Reichl:
> >> > For rk3399-roc-pc is a mezzanine board available that carries M.2 and
> >> > POE interfaces. Use it with a separate dts.
> >> >
> >> > Signed-off-by: Markus Reichl <m.reichl@fivetechno.de>
> >> > ---
> >> >  arch/arm64/boot/dts/rockchip/Makefile         |   1 +
> >> >  .../boot/dts/rockchip/rk3399-roc-pc-mezz.dts  |  52 ++
> >> >  .../arm64/boot/dts/rockchip/rk3399-roc-pc.dts | 757 +----------------
> >> >  .../boot/dts/rockchip/rk3399-roc-pc.dtsi      | 767 ++++++++++++++++++
> >> >  4 files changed, 821 insertions(+), 756 deletions(-)
> >> >  create mode 100644 arch/arm64/boot/dts/rockchip/rk3399-roc-pc-mezz.dts
> >> >  create mode 100644 arch/arm64/boot/dts/rockchip/rk3399-roc-pc.dtsi
> >> >
> >> > diff --git a/arch/arm64/boot/dts/rockchip/Makefile b/arch/arm64/boot/dts/rockchip/Makefile
> >> > index a959434ad46e..80ee9f1fc5f5 100644
> >> > --- a/arch/arm64/boot/dts/rockchip/Makefile
> >> > +++ b/arch/arm64/boot/dts/rockchip/Makefile
> >> > @@ -28,6 +28,7 @@ dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-nanopi-neo4.dtb
> >> >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-orangepi.dtb
> >> >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-puma-haikou.dtb
> >> >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-roc-pc.dtb
> >> > +dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-roc-pc-mezz.dtb
> >> >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-rock-pi-4.dtb
> >> >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-rock960.dtb
> >> >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-rockpro64.dtb
> >> > diff --git a/arch/arm64/boot/dts/rockchip/rk3399-roc-pc-mezz.dts b/arch/arm64/boot/dts/rockchip/rk3399-roc-pc-mezz.dts
> >> > new file mode 100644
> >> > index 000000000000..ee77677d2cf2
> >> > --- /dev/null
> >> > +++ b/arch/arm64/boot/dts/rockchip/rk3399-roc-pc-mezz.dts
> >> > @@ -0,0 +1,52 @@
> >> > +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
> >> > +/*
> >> > + * Copyright (c) 2017 T-Chip Intelligent Technology Co., Ltd
> >> > + * Copyright (c) 2019 Markus Reichl <m.reichl@fivetechno.de>
> >> > + */
> >> > +
> >> > +/dts-v1/;
> >> > +#include "rk3399-roc-pc.dtsi"
> >> > +
> >> > +/ {
> >> > +     model = "Firefly ROC-RK3399-PC Mezzanine Board";
> >> > +     compatible = "firefly,roc-rk3399-pc", "rockchip,rk3399";
> >>
> >> different board with same compatible isn't possible, so
> >> you'll need a new compatible for it and add a new line to
> >> the roc-pc entry in
> >>         Documentation/devicetree/bindings/arm/rockchip.yaml
> >>
> >> Either you see it as
> >> - a board + hat, using dt overlay and same compatible
> >> - a completely separate board, which needs a separate
> >>   compatible as well
> >>
> >> And as discussed in the previous thread
> >> http://lists.infradead.org/pipermail/linux-rockchip/2019-November/027592.html
> >> but also in Jagan's response that really is somehow a grey area
> >> for something relatively static as the M.2 extension.
> >
> > Sorry for late response on this. I still think that the "overlay would
> > be a better suite" than having separate dts, since it is HAT which is
> > optional to insert and have possibility of having another HAT if it
> > really fit into it.
> >
> > Comments?
> Presently no other extension board does exist, I don't expect one.
>
> I use it with rootfs on NVME on the mezzanine board.
> It is convenient to have the NVME up before going to user space.
>
> The board has SPI-NOR MTD storage to host U-Boot.
> In future U-Boot could boot from NVME directly without needing
> an SD or MMC to host the boot kernel.

This is purely a use-case scenario, I can still use SPI-NOR alone with
final boot via initramfs and use on board storage peripherals for
distributions separately. What I'm saying we can have overlay for
those are optional based on the user instead of making it for
constant.