Re: [PATCH v3 4/7] dt-bindings: timer: Add RISC-V ACLINT mtimer bindings

[Conor Dooley <conor@kernel.org>]

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On Mon, Nov 09, 2026 at 03:40:44PM +1030, Joel Stanley wrote:
> Document the RISC-V ACLINT mtimer and mtimecmp hardware, as described
> by the riscv-aclint specification, commit 4e570bfd3201f2 [2].
> 
> Multiple vendors are shipping silicon with the hardware as described
> by the specification, which was abandoned[1] as a standalone spec at
> v1.0-rc4.  As we have multiple instances of hardware that implement
> the spec, the widespread implementation of the spec is de facto
> ratification, providing a stationary target for the bindings to document
> and an exception to the policy of not accepting things that are
> pre-ratification.
> 
> [1] https://lists.riscv.org/g/tech-aia/topic/connections_between_aia_and/107177435
> [2] https://github.com/riscvarchive/riscv-aclint/blob/4e570bfd3201f2c09e5afd290b5091526b0f099a/riscv-aclint.adoc
> 
> Signed-off-by: Joel Stanley <joel@jms.id.au>
> ---
> v3:
>   - Rework commit message following discussion at LPC

Since I was one of the folks involved in that chat, I am okay with this
obviously. I was convinced to change my mind about the use of the riscv
vendor prefix because of the widespread adoption.

>   - Add reg-names, rework description, fix example
> ---
>  MAINTAINERS                                   |  1 +
>  .../bindings/timer/riscv,aclint-mtimer.yaml   | 56 +++++++++++++++++++
>  2 files changed, 57 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/timer/riscv,aclint-mtimer.yaml
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 93abbb315065..403875d5932e 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -24185,6 +24185,7 @@ S:	Maintained
>  T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tenstorrent/linux.git
>  F:	Documentation/devicetree/bindings/clock/tenstorrent,atlantis-prcm-rcpu.yaml
>  F:	Documentation/devicetree/bindings/riscv/tenstorrent.yaml

> +F:	Documentation/devicetree/bindings/timer/riscv,aclint-mtimer.yaml


>  F:	arch/riscv/boot/dts/tenstorrent/
>  F:	drivers/clk/tenstorrent/
>  F:	drivers/reset/reset-tenstorrent-atlantis.c
> diff --git a/Documentation/devicetree/bindings/timer/riscv,aclint-mtimer.yaml b/Documentation/devicetree/bindings/timer/riscv,aclint-mtimer.yaml
> new file mode 100644
> index 000000000000..e6f3d08d4f93
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/timer/riscv,aclint-mtimer.yaml
> @@ -0,0 +1,56 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/timer/riscv,aclint-mtimer.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: RISC-V Advanced Core Local Interruptor (ACLINT) timer
> +
> +maintainers:
> +  - Joel Stanley <jms@oss.tenstorrent.com>
> +
> +description:
> +  The RISC-V ACLINT specification defines a set of memory mapped devices which
> +  provide timer functionality for each hart on a multi-hart RISC-V platform.
> +  The mtimer device has a single mtime register and one mtimecmp register per
> +  hart. The specification is at https://github.com/riscvarchive/riscv-aclint/
> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +          - tenstorrent,atlantis-aclint-mtimer
> +      - const: riscv,aclint-mtimer

So, what are we doing about thead,c900-aclint-mtimer.yaml?

> +
> +  reg:
> +    items:
> +      - description: mtime register
> +      - description: mtimecmp registers

For example, I note that you have mtime and mtimecmp in the opposite
order to how the mips folks have had to add the mtime region to that
file:
https://lore.kernel.org/all/20261103-p8700-dts-v2-6-3ac5d49f2c37@htecgroup.com/

> +
> +  reg-names:
> +    items:
> +      - const: mtime
> +      - const: mtimecmp
> +
> +  interrupts-extended:
> +    minItems: 1
> +    maxItems: 4095
> +
> +required:
> +  - compatible
> +  - reg

You've also not made reg-names or interrupts-extended required.

I think we should swap the regs around and make these two required at a
minimum, but also "initialise" this file by renaming the existing file.

My ~assumption~hope is that all of the devices in that file have
implemented the aclint spec at the -rc1 revision that we're citing here.

> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    timer@a2180000 {
> +      compatible = "tenstorrent,atlantis-aclint-mtimer", "riscv,aclint-mtimer";
> +      reg = <0xa2180000 0x8000>, <0xa2188000 0x8000>;
> +      reg-names = "mtime", "mtimecmp";
> +      interrupts-extended = <&cpu1intc 7>,
> +                            <&cpu2intc 7>,
> +                            <&cpu3intc 7>,
> +                            <&cpu4intc 7>;
> +    };
> +...
> -- 
> 2.47.3
> 
> 

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