linux-kernel - Re: [PATCH 1/7] dt-bindings: soc: st: document the RISAB firewall peripheral

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Message-ID: <ee9759a6-1779-4891-8716-24c36134198a@kernel.org>
Date: Tue, 10 Feb 2026 08:57:28 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Gatien Chevallier <gatien.chevallier@...s.st.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>
Cc: devicetree@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] dt-bindings: soc: st: document the RISAB firewall
 peripheral

On 09/02/2026 15:59, Gatien Chevallier wrote:
> Add documentation on the RISAB peripheral that is a memory firewall on

What is RISAB? It's in capitals, so some sort of acronym?

> the stm32mp2x platforms.
> 
> Signed-off-by: Gatien Chevallier <gatien.chevallier@...s.st.com>
> ---
>  .../bindings/soc/st/st,stm32mp25-risab.yaml        | 74 ++++++++++++++++++++++

soc is not a dumping ground. Find suitable subsystem for it.


>  MAINTAINERS                                        |  5 ++
>  2 files changed, 79 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/soc/st/st,stm32mp25-risab.yaml b/Documentation/devicetree/bindings/soc/st/st,stm32mp25-risab.yaml
> new file mode 100644
> index 000000000000..d05a683c594d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/soc/st/st,stm32mp25-risab.yaml
> @@ -0,0 +1,74 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/soc/st/st,stm32mp25-risab.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: STM32 Resource isolation peripheral unit for address space protection
> +       (block-based)

So maybe here would be RISAB explanation... Use proper capital lettes in
the title (e.g. AP or Chicago style, I don't think we do any preference
or consistency, especially that most of us including myself don't even
know the difference).

> +
> +maintainers:
> +  - Gatien Chevallier <gatien.chevallier@...s.st.com>
> +
> +description:
> +  The RIF (resource isolation framework) is a comprehensive set of hardware
> +  blocks designed to enforce and manage isolation of STM32 hardware resources,
> +  like memory and peripherals. The RISAB peripheral is part of the RIF and is
> +  used to protect internal RAMs by applying access rights per RISAB fixed-size
> +  page. Through RISAB registers, a trusted domain, or the domain to whom the
> +  page configuration has been delegated, assigns memory pages to one or more
> +  security domains (secure, privilege, compartment).
> +
> +properties:
> +  compatible:
> +    const: st,stm32mp25-risab
> +
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    items:
> +      - description: RISAB bus clock
> +
> +  memory-region:
> +    minItems: 1
> +    maxItems: 32
> +    description:
> +      Phandle to nodes describing memory regions to be configured in the RISAB
> +      by the trusted domain of at least a RISAB page size.
> +      These regions cannot overlap. A zone must be within st,mem-map range and
> +      can be represented by one or more pages.
> +
> +  st,mem-map:
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +    description: Memory address range covered by the RISAB.
> +    items:
> +      - description: Memory range base address
> +      - description: Memory range size

Why do you need this property if you have memory-region already? This
also should be part of <reg>, although this mixing with memory-region is
anyway confusing.

> +
> +  st,srwiad:
> +    description:
> +      When set, the trusted domain configures the RISAB to allow secure
> +      read/write data accesses to non-secure blocks and pages. Secure execute
> +      remains illegal.
> +    type: boolean

Shouldn't this be a property of given block from memory-regions, not
entire RISAB?

> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +  - st,mem-map
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/clock/st,stm32mp25-rcc.h>
> +
> +    risab1: risab@...f0000 {

Drop unused label.

> +        compatible = "st,stm32mp25-risab";
> +        reg = <0x420f0000 0x1000>;
> +        clocks = <&rcc CK_ICN_LS_MCU>;
> +        st,mem-map = <0xa000000 0x20000>;
> +        st,srwiad;
> +    };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e08767323763..b9a1276e94a9 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -25092,6 +25092,11 @@ F:	Documentation/arch/arm/stm32/stm32-dma-mdma-chaining.rst
>  F:	Documentation/devicetree/bindings/dma/stm32/
>  F:	drivers/dma/stm32/
>  
> +STM32 SoC FIREWALL DRIVERS

s/SoC/SOC/


Best regards,
Krzysztof