Re: [PATCH v2 08/13] dt-bindings: riscv: Add descriptions for Za64rs, Ziccamoa, Ziccif, and Zicclsm

From: Alex Elder
Date: Sun Dec 28 2025 - 18:50:53 EST

On 12/27/25 10:10 PM, Guodong Xu wrote:
Hi, Alex, Conor

On Sat, Dec 27, 2025 at 5:28 AM Alex Elder <elder@xxxxxxxxxxxx> wrote:

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

Thank you for the review.

Together with the filenames, I also listed the Version numbers.

These are officially released versions of profile documents. I mean they
won't be changed without modifying the version number.

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.

Yes they are correct. As far as what stated in the two profile documents.


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?


Za64rs and Zicclsm: no, they are not 'A'. They are cache related.

Isn't a Za64rs reservation set related to atomic operations,
though? They are related to load-reserved/store conditional
instructions, which are introduced in the atomic instructions
section.

I was mistaken about Zicclsm, that's related to unaligned
accesses, but does not apply to atomic operations.

Ziccrse and Ziccamoa: yes, they are 'A' related.

Ziccrse specifies the main memory must support "RsrvEventual", which is one
(totally there are four) of the support level for Load-Reserved/
Store-Conditional (LR/SC) atomic instructions.

And in RVA profiles, two named features (exts) are added:
Ziccrse: which further define the level of LR/SC operations being supported.
Ziccamoa: which further define the level of AMOs instructions being supported.


We already know that "A" = Zaamo + Zalrsc;

In summary, the dependencies among these extensions are:
Ziccrse -> Zalrsc -> A;
Ziccamoa -> Zaamo -> A;

Furthermore, the A extension is already mandated by RVA23U64, so
is it really necessary to add this logic?

Hi, Conor

What do you think? I am kind of agree with Alex to remove the schema
checking logic.

Leaving the dependency check to riscv/cpufeature.c, let the .validate call
do the job. If you agree, I can remove the schema checking logic on Ziccamoa
and A in my next version.

Yes I think this is a better way to handle it. Conor?

Btw, cpufeature.c validate() deserves another patch/patchset.
I'll be happy to add that if we reach a consensus here.

Yes I think you should do this once there is concensus.






Signed-off-by: Guodong Xu <guodong@xxxxxxxxxxxx>
---
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

That is exactly what I am doing.

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):


I am using what the RVA23 Profile defines:
"Ziccamoa: Main memory supports all atomics in A"

I prefer to keep it as is.

That's fine. I don't think I felt strongly about any of the things
I said about the exact wording used here.

Thanks.

-Alex

BR,
Guodong

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: