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Message-ID: <8851c155-300a-4241-a5be-5163ba54e47c@riscstar.com>
Date: Fri, 26 Dec 2025 15:28:32 -0600
From: Alex Elder <elder@...cstar.com>
To: Guodong Xu <guodong@...cstar.com>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
<conor+dt@...nel.org>, Paul Walmsley <pjw@...nel.org>,
Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Alexandre Ghiti <alex@...ti.fr>, Yixun Lan <dlan@...too.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>,
Samuel Holland <samuel.holland@...ive.com>, Anup Patel
<anup@...infault.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>, Lubomir Rintel <lkundrak@...sk>,
Yangyu Chen <cyy@...self.name>
Cc: Paul Walmsley <paul.walmsley@...ive.com>, Conor Dooley
<conor@...nel.org>, Heinrich Schuchardt <xypron.glpk@....de>,
Kevin Meng Zhang <zhangmeng.kevin@...ux.spacemit.com>,
Andrew Jones <ajones@...tanamicro.com>, devicetree@...r.kernel.org,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
spacemit@...ts.linux.dev, linux-serial@...r.kernel.org
Subject: Re: [PATCH v2 08/13] dt-bindings: riscv: Add descriptions for Za64rs,
Ziccamoa, Ziccif, and Zicclsm
On 12/22/25 7:04 AM, Guodong Xu wrote:
> Add descriptions for four extensions: Za64rs, Ziccamoa, Ziccif, and
> Zicclsm. These extensions are ratified in RISC-V Profiles Version 1.0
> (commit b1d806605f87 "Updated to ratified state.").
I think stating the RISC-V profiles commit ID here (in the commit
header) is good.
I do *not* think it's necessary to include it in the descriptions
for the extensions, below, but I seem to be late to the party in
expressing this opinion...
That commit ID is related to this repository:
https://github.com/riscv/riscv-profiles.git
I have a few other comments below but generally I think what you
did looks good. I have one overall question though.
> They are introduced as new extension names for existing features and
> regulate implementation details for RISC-V Profile compliance. According
> to RISC-V Profiles Version 1.0 and RVA23 Profiles Version 1.0, they are
> mandatory for the following profiles:
>
> - za64rs: Mandatory in RVA22U64, RVA23U64
> - ziccamoa: Mandatory in RVA20U64, RVA22U64, RVA23U64
> - ziccif: Mandatory in RVA20U64, RVA22U64, RVA23U64
> - zicclsm: Mandatory in RVA20U64, RVA22U64, RVA23U64
I did not verify your statements about where these are
optional and mandatory, but I assume they're correct.
> Since Ziccamoa depends on the 'A' extension, add a schema check to
> enforce this dependency.
All of these extensions are related to atomic operations, right?
Don't *all* of them (not just Ziccamoa) depend on the A extension?
Furthermore, the A extension is already mandated by RVA23U64, so
is it really necessary to add this logic?
> Signed-off-by: Guodong Xu <guodong@...cstar.com>
> ---
> v2: New patch.
> ---
> .../devicetree/bindings/riscv/extensions.yaml | 34 ++++++++++++++++++++++
> 1 file changed, 34 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml
> index 385e1deb23996d294e7662693f1257f910a6e129..a6b9d7e3edf86ecfb117ba72e295ef097bdc9831 100644
> --- a/Documentation/devicetree/bindings/riscv/extensions.yaml
> +++ b/Documentation/devicetree/bindings/riscv/extensions.yaml
> @@ -237,6 +237,12 @@ properties:
> as ratified at commit 4a69197e5617 ("Update to ratified state") of
> riscv-svvptc.
>
> + - const: za64rs
> + description:
> + The standard Za64rs extension for reservation set size of at most
> + 64 bytes, as ratified in RISC-V Profiles Version 1.0, with commit
> + b1d806605f87 ("Updated to ratified state.")
The more complete description says:
Reservation sets are contiguous, naturally aligned, and a maximum
of 64 bytes.
But as I read on (below) I suppose using the more succinct description
from the glossary might be best, forcing people who care to go look
at the reference documents.
> +
> - const: zaamo
> description: |
> The standard Zaamo extension for atomic memory operations as
> @@ -378,6 +384,27 @@ properties:
> in commit 64074bc ("Update version numbers for Zfh/Zfinx") of
> riscv-isa-manual.
>
> + - const: ziccamoa
> + description:
> + The standard Ziccamoa extension for main memory (cacheability and
> + coherence) must support all atomics in A, as ratified in RISC-V
> + Profiles Version 1.0, with commit b1d806605f87 ("Updated to
> + ratified state.")
Similar comment here (but also with a similar caveat):
Main memory regions with both the cacheability and coherence PMAs
must support all atomics in A.
And I might say "the A extension", but maybe that's a bad idea.
> +
> + - const: ziccif
> + description:
> + The standard Ziccif extension for main memory (cacheability and
> + coherence) instruction fetch atomicity, as ratified in RISC-V
> + Profiles Version 1.0, with commit b1d806605f87 ("Updated to
> + ratified state.")
> +
> + - const: zicclsm
> + description:
> + The standard Zicclsm extension for main memory (cacheability and
> + coherence) must support misaligned loads and stores, as ratified
> + in RISC-V Profiles Version 1.0, with commit b1d806605f87 ("Updated
> + to ratified state.")
> +
> - const: ziccrse
> description:
> The standard Ziccrse extension which provides forward progress
> @@ -795,6 +822,13 @@ properties:
> then:
> contains:
> const: f
> + # Ziccamoa depends on A
Maybe more than just depends on the A extension.
-Alex
> + - if:
> + contains:
> + const: ziccamoa
> + then:
> + contains:
> + const: a
> # Zvfbfmin depends on V or Zve32f
> - if:
> contains:
>
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