linux-kernel - Re: [PATCH v3 03/12] dt-bindings: bus: document the stm32 debug bus

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Message-ID: <f3250e5e-5fa0-4730-8e0c-14d35bcc0705@foss.st.com>
Date: Thu, 22 Jan 2026 15:13:15 +0100
From: Gatien CHEVALLIER <gatien.chevallier@...s.st.com>
To: Rob Herring <robh@...nel.org>
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 v3 03/12] dt-bindings: bus: document the stm32 debug bus



On 1/21/26 16:21, Rob Herring wrote:
> On Wed, Jan 21, 2026 at 01:34:37PM +0100, 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        | 79 ++++++++++++++++++++++
>>   1 file changed, 79 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..2db35e41e76c
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/bus/st,stm32mp131-dbg-bus.yaml
>> @@ -0,0 +1,79 @@
>> +# 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
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  "#access-controller-cells":
>> +    const: 1
>> +    description:
>> +      Contains the debug profile necessary to access the peripheral.
>> +
>> +patternProperties:
>> +  "^.*@[0-9a-f]+$":
>> +    description: Debug related peripherals
>> +    type: object
>> +
>> +    additionalProperties: true
>> +
>> +    required:
>> +      - access-controllers
>> +
>> +required:
>> +  - "#access-controller-cells"
>> +  - "#address-cells"
>> +  - "#size-cells"
>> +  - compatible
>> +  - ranges
>> +  - reg
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    #include <dt-bindings/clock/stm32mp1-clks.h>
>> +
>> +    dbg_bus: bus@...80000 {
>> +      compatible = "st,stm32mp131-dbg-bus";
>> +      reg = <0x50080000 0x3f80000>;
> 
> That's a lot of registers... Yet the bus driver doesn't access any.
> Looks to me like this belongs in ranges instead if there aren't any bus
> registers. Or its size should be just the registers and then the whole
> region size goes in ranges.
> 

Hello Rob,

Understandable comment. I'll switch to defining the range in the
ranges property in the V3.

Thank you,
Gatien

>> +      #address-cells = <1>;
>> +      #size-cells = <1>;
>> +      #access-controller-cells = <1>;
>> +      ranges;
>> +
>> +      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>;
>> +      };
>> +    };
>>
>> -- 
>> 2.43.0
>>