[PATCH v3] arm64: renesas: Add TFA BL31 handoff support on Renesas R-Car Gen4

[Quentin Schulz]

Hi Marek,

On 3/2/25 9:59 PM, Marek Vasut wrote:
> Implement custom U_BOOT_FIT_LOADABLE_HANDLER and armv8_switch_to_el2_prep()
> handling in case the TFA was loaded. The loadables handler sets up custom
> handoff structure used by Renesas TFA fork in fixed location in DRAM and
> indicates the TFA has been loaded.
> 
> The custom armv8_switch_to_el2_prep() handling tests whether the TFA BL31
> was previously loaded and the custom handoff structure was set up, and if
> so, jumps to TFA BL31 which switches from EL3 to EL2 and then returns to
> U-Boot just past bl in armv8_switch_to_el2() to finish starting the Linux
> kernel.
> 
> The jump to Linux through TFA works in such a way that the custom
> armv8_switch_to_el2_prep() handler configures the custom handoff structure
> such that the target jump address of the TFA BL31 on exit is set to the
> armv8_switch_to_el2() + 4, which is just past the bl, and just before the
> U-Boot code which implements the Linux kernel boot from either EL. The
> registers passed through the TFA BL31 are all the registers passed into
> armv8_switch_to_el2_prep() to assure maximum compatibility with all the
> boot modes. The armv8_switch_to_el2_prep() handler jumps to the TFA BL31,
> which does its setup, drops EL from EL3 to EL2 and finally jumps to the
> armv8_switch_to_el2() + 4 entry point, which then allows U-Boot to boot
> the Linux kernel the usual way.
> 
> In order to build suitable kernel fitImage, build TFA first, upstream
> is currently under review:
> https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/35799
> Or if necessary, downstream repository:
> remote: https://github.com/renesas-rcar/arm-trusted-firmware.git
> branch: rcar_gen4_v2.7_v4x
> 
> ```
> $ git clean -fqdx
> $ MBEDTLS_DIR=/path/to/mbedtls/ make -j$(nproc) bl31 \
> 	PLAT=rcar_gen4 ARCH=aarch64 LSI=V4H SPD=none \
> 	CTX_INCLUDE_AARCH32_REGS=0 MBEDTLS_COMMON_MK=1 \
> 	PTP_NONSECURE_ACCESS=1 LOG_LEVEL=20 DEBUG=0 \
> 	ENABLE_ASSERTIONS=0 E=0
> ```
> 
> Build Linux kernel Image and device tree from current mainline Linux
> kernel repository, obtain 'Image' and 'r8a779g0-white-hawk.dtb' .
> 
> Bundle the files together using provided fit-image.its fitImage description:
> ```
> $ mkimage -f fit-image.its fitImage
> ```
> 
> To start the kernel fiImage generated in previous step, load fitImage
> to DRAM and use the 'bootm' command to start it:
> => load 0x58000000 ... fitImage && bootm 0x58000000
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
> ---
> Cc: Andre Przywara <andre.przywara at arm.com>
> Cc: Caleb Connolly <caleb.connolly at linaro.org>
> Cc: Igor Opaniuk <igor.opaniuk at gmail.com>
> Cc: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> Cc: Julien Masson <jmasson at baylibre.com>
> Cc: Mattijs Korpershoek <mkorpershoek at baylibre.com>
> Cc: Maxim Moskalets <maximmosk4 at gmail.com>
> Cc: Michael Walle <mwalle at kernel.org>
> Cc: Nobuhiro Iwamatsu <iwamatsu at nigauri.org>
> Cc: Patrick Rudolph <patrick.rudolph at 9elements.com>
> Cc: Paul Barker <paul.barker.ct at bp.renesas.com>
> Cc: Paul-Erwan Rio <paulerwan.rio at gmail.com>
> Cc: Peter Hoyes <Peter.Hoyes at arm.com>
> Cc: Quentin Schulz <quentin.schulz at cherry.de>
> Cc: Raymond Mao <raymond.mao at linaro.org>
> Cc: Sam Protsenko <semen.protsenko at linaro.org>
> Cc: Simon Glass <sjg at chromium.org>
> Cc: Sughosh Ganu <sughosh.ganu at linaro.org>
> Cc: Tom Rini <trini at konsulko.com>
> Cc: u-boot at lists.denx.de
> ---
> V2: Only start the BL31 if running in EL3
> V3: Update link to upstream TFA BL31 posting
> ---
>   board/renesas/common/gen4-common.c | 126 +++++++++++++++++++++++++++++
>   1 file changed, 126 insertions(+)
> 
> diff --git a/board/renesas/common/gen4-common.c b/board/renesas/common/gen4-common.c
> index 52a0639073b..f7d129be4c8 100644
> --- a/board/renesas/common/gen4-common.c
> +++ b/board/renesas/common/gen4-common.c

I'm wondering if it really makes sense to have this in board/? If I 
understood correctly, this is all SoC-specific? So shouldn't that rather 
be in arch/arm/mach-renesas maybe? So that boards based on an R-Car gen4 
SoC don't have to set SYS_VENDOR to renesas or copy the code in their 
own board/<vendor>/common directory?

What do you think?

Cheers,
Quentin