Re: [PATCH v2 14/14] arm64: dts: rockchip: Add rock5b overlays for PCIe endpoint mode

[Niklas Cassel <cassel@kernel.org>]

On Sun, May 05, 2024 at 02:14:45PM +0200, Heiko Stübner wrote:
> Am Samstag, 4. Mai 2024, 19:37:30 CEST schrieb Manivannan Sadhasivam:
> > On Tue, Apr 30, 2024 at 02:01:11PM +0200, Niklas Cassel wrote:
> > > Add rock5b overlays for PCIe endpoint mode support.
> > > 
> > 
> > I'm not aware of mainline using overlays. Is this a new one?
> 
> I guess you could still call it new'ish ;-)
> 
> But the mainline kernel does carry a number of overlays already [0] .
> This does of course not handle the actual application of overlays,
> which I guess bootloaders do only at this point.

Yes, AFAICT, the actual application is handled by bootloaders.
(Well, there is a "Overlay in-kernel API", but not a user API.)


> > > diff --git a/arch/arm64/boot/dts/rockchip/Makefile b/arch/arm64/boot/dts/rockchip/Makefile
> > > index f906a868b71a..d827432d5111 100644
> > > --- a/arch/arm64/boot/dts/rockchip/Makefile
> > > +++ b/arch/arm64/boot/dts/rockchip/Makefile
> > > @@ -117,6 +117,8 @@ dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588-nanopc-t6.dtb
> > >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588-orangepi-5-plus.dtb
> > >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588-quartzpro64.dtb
> > >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588-rock-5b.dtb
> > > +dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588-rock-5b-pcie-ep.dtbo
> > > +dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588-rock-5b-pcie-srns.dtbo
> > >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588-tiger-haikou.dtb
> > >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588-toybrick-x0.dtb
> > >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588-turing-rk1.dtb
> > > @@ -127,3 +129,6 @@ dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588s-nanopi-r6s.dtb
> > >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588s-nanopi-r6c.dtb
> > >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588s-rock-5a.dtb
> > >  dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588s-orangepi-5.dtb
> > > +
> > > +# Enable support for device-tree overlays
> > > +DTC_FLAGS_rk3588-rock-5b += -@

Note that this DTC compiler flag is needed for the overlay for the
bootloader to be able to apply the overlay successfully.

(In order to supply the .dtbo compiled by the kernel directly to u-boot.)

I'm not sure how the other rockchip overlays compiled by the kernel can
work when suppling them to u-boot.

I'm guessing that they compile them externally/manually outside the source
tree with the -@ flag enabled.


If we look at other arm64 device tree overlays in the kernel, e.g. TI,
they seem to supply -@ for all their .dtso files:

$ git grep -- "-@" arch/arm64/


Kind regards,
Niklas