linux-kernel - Re: [PATCH v4 03/12] dt-bindings: bus: document the stm32 debug bus

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Message-ID: <20260122232139.GA3717629-robh@kernel.org>
Date: Thu, 22 Jan 2026 17:21:39 -0600
From: Rob Herring <robh@...nel.org>
To: Gatien CHEVALLIER <gatien.chevallier@...s.st.com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
	Mike Leach <mike.leach@...aro.org>,
	James Clark <james.clark@...aro.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Leo Yan <leo.yan@...ux.dev>,
	Clément Le Goffic <legoffic.clement@...il.com>,
	Linus Walleij <linusw@...nel.org>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	jens.wiklander@...aro.org, coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH v4 03/12] dt-bindings: bus: document the stm32 debug bus

On Thu, Jan 22, 2026 at 05:22:21PM +0100, Gatien CHEVALLIER wrote:
> 
> 
> On 1/22/26 17:19, Gatien Chevallier wrote:
> > Document the stm32 debug bus. The debug bus is responsible for
> > checking the debug sub-system accessibility before probing any related
> > drivers.
> > 
> > Signed-off-by: Gatien Chevallier <gatien.chevallier@...s.st.com>
> > ---
> >   .../bindings/bus/st,stm32mp131-dbg-bus.yaml        | 77 ++++++++++++++++++++++
> >   1 file changed, 77 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/bus/st,stm32mp131-dbg-bus.yaml b/Documentation/devicetree/bindings/bus/st,stm32mp131-dbg-bus.yaml
> > new file mode 100644
> > index 000000000000..57f01d301e75
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/bus/st,stm32mp131-dbg-bus.yaml
> > @@ -0,0 +1,77 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/bus/st,stm32mp131-dbg-bus.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: STM32 Coresight bus
> > +
> > +maintainers:
> > +  - Gatien Chevallier <gatien.chevallier@...s.st.com>
> > +
> > +description:
> > +  The STM32 debug bus is in charge of checking the debug configuration
> > +  of the platform before probing the peripheral drivers that rely on the debug
> > +  domain.
> > +
> > +properties:
> > +  compatible:
> > +    items:
> > +      - enum:
> > +          - st,stm32mp131-dbg-bus
> > +          - st,stm32mp151-dbg-bus
> > +
> > +  "#address-cells":
> > +    const: 1
> > +
> > +  "#size-cells":
> > +    const: 1
> > +
> > +  ranges: true
> 
> Maybe maxItems:2 is preferred here, no?

Wouldn't it be 1 as there is only 1 range? Up to you whether you want to 
limit it or not.

> 
> > +
> > +  reg:
> > +    maxItems: 1

Should be dropped?

> > +
> > +  "#access-controller-cells":
> > +    const: 1
> > +    description:
> > +      Contains the debug profile necessary to access the peripheral.
> > +
> > +patternProperties:
> > +  "^.*@[0-9a-f]+$":

This can be: "@[0-9a-f]+$"

> > +    description: Debug related peripherals
> > +    type: object
> > +
> > +    additionalProperties: true
> > +
> > +    required:
> > +      - access-controllers
> > +
> > +required:
> > +  - "#access-controller-cells"
> > +  - "#address-cells"
> > +  - "#size-cells"
> > +  - compatible
> > +  - ranges
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/clock/stm32mp1-clks.h>
> > +
> > +    dbg_bus: bus@...80000 {

Drop unused labels.

> > +      compatible = "st,stm32mp131-dbg-bus";
> > +      #address-cells = <1>;
> > +      #size-cells = <1>;
> > +      #access-controller-cells = <1>;
> > +      ranges = <0x50080000 0x50080000 0x3f80000>;
> > +
> > +      cs_cti_trace: cti@...94000 {
> > +        compatible = "arm,coresight-cti", "arm,primecell";
> > +        reg = <0x50094000 0x1000>;
> > +        clocks = <&rcc CK_DBG>;
> > +        clock-names = "apb_pclk";
> > +        access-controllers = <&dbg_bus 0>;
> > +      };
> > +    };
> > 
>