linux-kernel - Re: [PATCH v4 3/5] dt-bindings: bus: Add STM32 ETZPC firewall controller

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Date:   Mon, 20 Jul 2020 09:21:35 +0000
From:   Benjamin GAIGNARD <benjamin.gaignard@...com>
To:     Rob Herring <robh@...nel.org>
CC:     "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stefano.stabellini@...inx.com" <stefano.stabellini@...inx.com>,
        "tomase@...inx.com" <tomase@...inx.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 3/5] dt-bindings: bus: Add STM32 ETZPC firewall
 controller



On 7/13/20 7:05 PM, Rob Herring wrote:
> On Wed, Jul 01, 2020 at 03:25:21PM +0200, Benjamin Gaignard wrote:
>> Document STM32 ETZPC firewall controller bindings
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...com>
>> ---
>>   .../bindings/bus/stm32/st,stm32-etzpc.yaml         | 46 ++++++++++++++++++++++
>>   1 file changed, 46 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/bus/stm32/st,stm32-etzpc.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/bus/stm32/st,stm32-etzpc.yaml b/Documentation/devicetree/bindings/bus/stm32/st,stm32-etzpc.yaml
>> new file mode 100644
>> index 000000000000..d92865fda40c
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/bus/stm32/st,stm32-etzpc.yaml
>> @@ -0,0 +1,46 @@
>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/bus/stm32/st,stm32-etzpc.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: STM32 Extended TrustZone Protection controller
>> +
>> +maintainers:
>> +  - Benjamin Gaignard <benjamin.gaignard@...com>
>> +
>> +description: STMicroelectronics's STM32 firewall bus controller implementation
>> +
>> +allOf:
>> +  - $ref: "firewall-provider.yaml#"
>> +  - $ref: /schemas/simple-bus.yaml#
> Your bus has controls/setup, it's not a simple-bus.
>
> Do you expect an old kernel or one with support for "st,stm32-etzpc-bus"
> disabled to work? How's it going to know if certain nodes can't be
> accessed without that support?
It already works with simple bus.
The goal behind implementing firewall bus controllers is to expose this 
in the DT
rather than hide it in the boot stages.

>
>> +
>> +properties:
>> +  compatible:
>> +    contains:
>> +      enum:
>> +        - st,stm32-etzpc-bus
>> +
>> +  reg:
>> +   maxItems: 1
>> +
>> +  '#firewall-cells':
>> +    const: 2
>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - '#firewall-cells'
>> +
>> +examples:
>> +  - |
>> +    soc@...07000 {
>> +      compatible = "st,stm32-etzpc-bus", "simple-bus";
>> +      reg = <0x5c007000 0x400>;
>> +      #firewall-cells = <2>;
>> +      #address-cells = <1>;
>> +      #size-cells = <1>;
>> +      ranges;
>> +    };
>> +
>> +...
>> -- 
>> 2.15.0
>>