Re: [PATCH v2 10/10] doc: falcon: Describe booting the OS through TF-A

Hi Simon,

On Tue, Aug 4, 2026 at 5:04=E2=80=AFPM Simon Glass <[email protected]> wrote=
:
>
> Hi Alexey,
>
> On 2026-07-31T17:10:44, Alexey Charkov <[email protected]> wrote:
> > doc: falcon: Describe booting the OS through TF-A
> >
> > Falcon Mode documentation only covers SPL entering the kernel itself, w=
hich
> > is not what happens on ARM64 SoCs needing ARM Trusted Firmware resident=
 to
> > provide firmware services: SPL loads a FIT holding BL31 as its firmware
> > image and the kernel as a loadable, and BL31 enters the kernel as BL33.
> >
> > Describe that flow, what the kernel image may be given that neither
> > booti_setup() nor bootz_setup() runs, how it differs from the classic f=
low,
> > and how to configure and build it on Rockchip.
> >
> > Signed-off-by: Alexey Charkov <[email protected]>
> >
> > doc/board/rockchip/rockchip.rst |   9 +++
> >  doc/develop/falcon.rst          | 131 ++++++++++++++++++++++++++++++++=
+++++++-
> >  2 files changed, 138 insertions(+), 2 deletions(-)
>
> > diff --git a/doc/board/rockchip/rockchip.rst b/doc/board/rockchip/rockc=
hip.rst
> > @@ -321,6 +321,15 @@ To build rk3588 boards:
> > +Falcon mode
> > +"""""""""""
> > +
> > +ARM64 Rockchip SoCs can also boot Linux straight from SPL through TF-A=
,
> > +without U-Boot proper running at all. Enabling CONFIG_ROCKCHIP_FALCON_=
IMAGE
> > +makes binman build a ``u-boot-rockchip-falcon.itb`` holding TF-A, the =
kernel
> > +and an optional initramfs, which are passed in with LINUX_KERNEL and
> > +LINUX_INITRD. See :doc:`../../develop/falcon` for the details.
>
> Please point at the rockchip-falcon.config fragment here as the easy
> on-ramp - patch 9 adds it precisely so users do not have to hand-edit
> their defconfig, but nothing in either doc actually tells them to use
> it. A one-liner like 'make <board>_defconfig rockchip-falcon.config'
> would make the story complete.

Makes sense, will add, thank you!

> > diff --git a/doc/develop/falcon.rst b/doc/develop/falcon.rst
> > @@ -95,11 +95,138 @@ Function that a board must implement
> > +SPL picks BL33 in spl_invoke_atf(), which looks for an image with
> > +``os =3D "linux"`` in the ``/fit-images`` node it appended to the devi=
ce tree
> > +and falls back to ``os =3D "u-boot"``. The kernel is entered at EL2 wi=
th the
> > +device tree address in x0, as the arm64 boot protocol requires.
>
> Just to clarify - the fallback to os =3D "u-boot" only happens outside
> secure Falcon mode, which is stated a paragraph later but reads as
> contradictory on first pass. Consider folding the exception into this
> sentence.

Ack

> > diff --git a/doc/develop/falcon.rst b/doc/develop/falcon.rst
> > @@ -95,11 +95,138 @@ Function that a board must implement
> > +CONFIG_SPL_UFS_RAW_OS_DEVNUM and CONFIG_SPL_UFS_RAW_OS_SECTOR against
> > +CONFIG_SPL_UFS_RAW_U_BOOT_DEVNUM and CONFIG_SPL_UFS_RAW_U_BOOT_SECTOR,=
 so
>
> 'against' reads oddly here - I'd suggest 'versus' or just 'and', with
> a comma before 'so'.

Ack

> > diff --git a/doc/develop/falcon.rst b/doc/develop/falcon.rst
> > @@ -95,11 +95,138 @@ Function that a board must implement
> > +DRAM which clear BL31 and OP-TEE, and can be adjusted with
> > +CONFIG_ROCKCHIP_FALCON_KERNEL_LOAD and friends.
>
> Please spell out the 'friends' - CONFIG_ROCKCHIP_FALCON_FDT_LOAD and
> CONFIG_ROCKCHIP_FALCON_INITRD_LOAD

Ack

> > diff --git a/doc/develop/falcon.rst b/doc/develop/falcon.rst
> > @@ -95,11 +95,138 @@ Function that a board must implement
> > +Enabling CONFIG_SPL_LZMA or CONFIG_SPL_GZIP additionally compresses th=
e
> > +kernel in the image, trading some decompression time for a smaller one=
 - for
> > +a 30 MiB arm64 Image, roughly 35% of the original with LZMA and 39% wi=
th
> > +gzip. Note that this compresses U-Boot itself as well, since both use =
the
> > +same setting.
>
> Just to check - is 'compresses U-Boot itself as well' actually true
> for the Falcon-only image (u-boot-rockchip-falcon.itb), which by name
> does not contain U-Boot proper? I think you mean the same
> SPL_LZMA/SPL_GZIP knob also compresses U-Boot in the regular
> u-boot.itb built alongside. Worth rewording to make that unambiguous.

Yes, I meant that the same Kconfig option applies to the U-Boot FIT
creation (not just Falcon) because of how the current binman template
for Rockchip is organized. Will reword, thank you for highlighting.

Best regards,
Alexey