[PATCH 0/7] Add support for RPMI to U-Boot
Anup Patel
anup at brainfault.org
Sun Jun 28 07:07:33 CEST 2026
On Sat, Jun 27, 2026 at 1:46 AM Charles Perry
<charles.perry at microchip.com> wrote:
>
> Hello,
>
> This series adds support for RISC-V Platform Management Interface (RPMI) to
> U-Boot. RPMI is an OS-agnostic protocol for communication between an
> Application Processor (AP) and a Platform Microcontroller (PuC) [1]. The
> goals and purpose of RPMI are similar to ARM's SCMI.
>
> This patchset first adds an abstraction layer for the transport
> (UCLASS_RPMI), then adds two transport layer (SBI MPXY and shared memory)
> and finally adds two client, or service group in RPMI jargon: Clock and
> device power service groups.
>
> This series also include a sandbox mode for which the RPMI transport
> doesn't attach to a firmware but contains a simulation of a firmware. This
> reuses code from librpmi [2] to create the message responses.
>
> Apart from the spec [1], this series reuses code from the Linux SBI MPXY
> driver [3], OpenSBI shared memory transport [4] and Linux RPMI clock driver
> [5].
>
> This was tested on a PIC64-HPSC SoC which features an application cluster
> and a system controller with isolated address spaces, hence the need for
> RPMI. I've tested the interoperability between RPMI clients and transports
> with an S-Mode U-boot (using the MPXY transport) and M-Mode U-Boot (using
> shared memory transport) and the following device tree fragment:
>
> ```
> firmware {
> rpmi: mailbox at 7000000000 {
> compatible = "riscv,rpmi-shmem-mbox";
> reg = <0x70 0x00000000 0x0 0x3000>,
> <0x70 0x00003000 0x0 0x3000>,
> <0x70 0x00006000 0x0 0x1000>,
> <0x70 0x00007000 0x0 0x1000>;
> reg-names = "a2p-req", "p2a-ack", "p2a-req", "a2p-ack";
> riscv,slot-size = <64>;
> #mbox-cells = <1>;
> };
>
> ifndef CONFIG_RISCV_MMODE
> clock-service {
> compatible = "riscv,rpmi-mpxy-clock";
> mboxes = <&rpmi 0x8>;
> riscv,sbi-mpxy-channel-id = <0x1000>;
> };
>
> device-power-service {
> compatible = "riscv,rpmi-mpxy-device-power";
> mboxes = <&rpmi 0x9>;
> riscv,sbi-mpxy-channel-id = <0x1001>;
> };
>
> mpxy_mbox: mailbox {
> compatible = "riscv,sbi-mpxy-mbox";
> #mbox-cells = <2>;
> };
> endif
>
> sysc_clk: clock-controller {
> compatible = "riscv,rpmi-clock";
> ifdef CONFIG_RISCV_MMODE
> mboxes = <&rpmi 0x8>;
> else
> mboxes = <&mpxy_mbox 0x1000 0x0>;
> endif
> #clock-cells = <1>;
> };
>
> sysc_dpwr: power-domain-controller {
> compatible = "riscv,rpmi-device-power";
> ifdef CONFIG_RISCV_MMODE
> mboxes = <&rpmi 0x9>;
> else
> mboxes = <&mpxy_mbox 0x1001 0x0>;
> endif
> #power-domain-cells = <1>;
> };
> };
> ```
>
> [1]: https://github.com/riscv-non-isa/riscv-rpmi
> [2]: https://github.com/riscv-software-src/librpmi
> [3]: https://elixir.bootlin.com/linux/v7.0.10/source/drivers/mailbox/riscv-sbi-mpxy-mbox.c
> [4]: https://elixir.bootlin.com/opensbi/v1.8.1/source/lib/utils/mailbox/fdt_mailbox_rpmi_shmem.c
> [5]: https://elixir.bootlin.com/linux/v7.0.10/source/drivers/clk/clk-rpmi.c
>
> Cc: Rahul Pathak <rahul at summations.net>
> Cc: Anup Patel <anup at brainfault.org>
> Cc: Paul Walmsley <pjw at kernel.org>
> Cc: Palmer Dabbelt <palmer at dabbelt.com>
> Cc: Albert Ou <aou at eecs.berkeley.edu>
> Cc: Alexandre Ghiti <alex at ghiti.fr>
> Cc: Romain Caritey <romain.caritey at microchip.com>
> Cc: Mame Maria Mbaye <MameMaria.Mbaye at microchip.com>
> Cc: Tom Rini <trini at konsulko.com>
> Cc: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> Cc: Rick Chen <rick at andestech.com>
> Cc: Leo Yu-Chi Liang <ycliang at andestech.com>
>
> Charles Perry (7):
> firmware: add support for RPMI
> firmware: rpmi: add support for the SBI MPXY transport
> firmware: rpmi: add support for shared memory transport
> drivers: clk: add support for RPMI clocks
> drivers: power: add support for RPMI power domains
> firmware: rpmi: add a test and a sandbox driver
> firmware: rpmi: add a test and sandbox for device power
I have a more general question.
Why add separate firmware framework for RPMI ?
You can just extend the existing U-Boot mailbox framework
and just like we have in Linux. The separate transport drivers
will be mailbox-controller drivers and each service group will
have a separate mailbox-client driver under appropriate driver
subsystem.
>
> MAINTAINERS | 9 +
> arch/riscv/include/asm/sbi.h | 57 +++
> arch/sandbox/dts/test.dts | 23 +
> configs/sandbox_defconfig | 3 +
> drivers/clk/Kconfig | 7 +
> drivers/clk/Makefile | 1 +
> drivers/clk/clk_rpmi.c | 346 +++++++++++++++
> drivers/firmware/Kconfig | 1 +
> drivers/firmware/Makefile | 1 +
> drivers/firmware/rpmi/Kconfig | 27 ++
> drivers/firmware/rpmi/Makefile | 4 +
> drivers/firmware/rpmi/rpmi-sandbox-clock.c | 446 +++++++++++++++++++
> drivers/firmware/rpmi/rpmi-sandbox-power.c | 174 ++++++++
> drivers/firmware/rpmi/rpmi-sandbox.c | 158 +++++++
> drivers/firmware/rpmi/rpmi-sandbox.h | 48 +++
> drivers/firmware/rpmi/rpmi-sbi-mpxy.c | 449 +++++++++++++++++++
> drivers/firmware/rpmi/rpmi-shmem.c | 474 +++++++++++++++++++++
> drivers/firmware/rpmi/rpmi-uclass.c | 138 ++++++
> drivers/power/domain/Kconfig | 7 +
> drivers/power/domain/Makefile | 1 +
> drivers/power/domain/rpmi-power-domain.c | 229 ++++++++++
> include/dm/uclass-id.h | 1 +
> include/rpmi-uclass.h | 79 ++++
> include/rpmi.h | 159 +++++++
> include/rpmi_proto.h | 143 +++++++
> test/dm/Makefile | 1 +
> test/dm/rpmi.c | 69 +++
> 27 files changed, 3055 insertions(+)
> create mode 100644 drivers/clk/clk_rpmi.c
> create mode 100644 drivers/firmware/rpmi/Kconfig
> create mode 100644 drivers/firmware/rpmi/Makefile
> create mode 100644 drivers/firmware/rpmi/rpmi-sandbox-clock.c
> create mode 100644 drivers/firmware/rpmi/rpmi-sandbox-power.c
> create mode 100644 drivers/firmware/rpmi/rpmi-sandbox.c
> create mode 100644 drivers/firmware/rpmi/rpmi-sandbox.h
> create mode 100644 drivers/firmware/rpmi/rpmi-sbi-mpxy.c
> create mode 100644 drivers/firmware/rpmi/rpmi-shmem.c
> create mode 100644 drivers/firmware/rpmi/rpmi-uclass.c
> create mode 100644 drivers/power/domain/rpmi-power-domain.c
> create mode 100644 include/rpmi-uclass.h
> create mode 100644 include/rpmi.h
> create mode 100644 include/rpmi_proto.h
> create mode 100644 test/dm/rpmi.c
>
> --
> 2.47.3
>
Regards,
Anup
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