Re: [RFC PATCH 2/7] dt-bindings: bus: add STM32 System Bus

[Gatien CHEVALLIER]

Hello,

On 12/22/22 11:24, Krzysztof Kozlowski wrote:
> On 21/12/2022 18:30, Gatien Chevallier wrote:
> > Document STM32 System Bus. This bus is intended to control firewall
> > access for the peripherals connected to it.
> >
> > Signed-off-by: Loic PALLARDY <loic.pallardy@xxxxxx>
> > Signed-off-by: Gatien Chevallier <gatien.chevallier@xxxxxxxxxxx>
>
> Please use scripts/get_maintainers.pl to get a list of necessary people
> and lists to CC.  It might happen, that command when run on an older
> kernel, gives you outdated entries.  Therefore please be sure you base
> your patches on recent Linux kernel
As it is based on Oleksii's patchset and older threads:
[1]: 
https://lore.kernel.org/all/20190318100605.29120-1-benjamin.gaignard@xxxxxx/
[2]: 
https://lore.kernel.org/all/20200701132523.32533-1-benjamin.gaignard@xxxxxx/

I wanted to include people that have already been included or 
participated in these.

I'm sorry I did miss/added some (extra) people. I will double-check for 
next patchset version.

> > ---
> >   .../devicetree/bindings/bus/st,sys-bus.yaml   | 88 +++++++++++++++++++
> >   1 file changed, 88 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/bus/st,sys-bus.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/bus/st,sys-bus.yaml b/Documentation/devicetree/bindings/bus/st,sys-bus.yaml
> > new file mode 100644
> > index 000000000000..9c0e86612695
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/bus/st,sys-bus.yaml
> > @@ -0,0 +1,88 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/bus/stm32,sys-bus.yaml
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title:  STM32 System Bus
>
> Only one space.

Ack. I already pushed a V2, that is now outdated with your review, where 
this error is fixed.

> > +
> > +description: |
> > +  The STM32 System Bus is an internal bus to which some internal peripherals
> > +  are connected. STM32 System Bus integrates a firewall controlling access to each
> > +  device. This bus prevents non-accessible devices to be probed.
> > +
> > +  To see which peripherals are securable, please check the SoC reference manual.
> > +
> > +maintainers:
> > +  - Gatien Chevallier <gatien.chevallier@xxxxxxxxxxx>
> > +
> > +allOf:
> > +  - $ref: /schemas/feature-controllers/feature-domain-controller.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - st,stm32mp13-sys-bus
> > +      - st,stm32mp15-sys-bus
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  "#address-cells":
> > +    const: 1
> > +
> > +  "#size-cells":
> > +    const: 1
> > +
> > +  '#feature-domain-cells':
>
> Use consistent quotes, either ' or "

Ack, will change in V3.

> > +    minItems: 1
>
> No. Cells must be const. This does not match cells at all...

Ack, will change to const in V3. What do imply by saying it does not 
match? Note that I've changed it to "minimum" in V2.

> > +
> > +  ranges: true
> > +
> > +  feature-domain-controller: true
> > +
> > +patternProperties:
> > +  "^.*@[0-9a-f]+$":
> > +    description: Devices attached to system bus
> > +    type: object
> > +    properties:
> > +      feature-domains:
> > +        $ref: /schemas/feature-controllers/feature-domain-controller.yaml#/properties/feature-domains
>
> maxItems

I don't think setting a max here is relevant as there can be numerous 
feature-domains referenced.

Maybe a min?

> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - "#address-cells"
> > +  - "#size-cells"
> > +  - feature-domain-controller
> > +  - '#feature-domain-cells'
> > +  - ranges
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    // In this example,
> > +    // - the foo1 device refers to etzpc as his domain controller.
> > +    // - same goes for foo2.
> > +    // Access rights are verified before creating devices.
> > +
> > +    etzpc: etzpc@5c007000 {
>
> Node names should be generic.
> https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation

Ack, will change to "etzpc: bus@5c007000" in V3

> > +        compatible = "st,stm32mp15-sys-bus";
> > +        reg = <0x5c007000 0x400>;
> > +        #address-cells = <1>;
> > +        #size-cells = <1>;
> > +        ranges;
> > +        feature-domain-controller;
> > +        #feature-domain-cells = <1>;
> > +
> > +        foo1: foo@1000000 {
>
> Node names should be generic.
> https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation

Here, if I use real peripherals, I have an issue with the dependency to 
YAML files. The feature-domains property is not defined in their 
bindings. Therefore, the dt_binding_check fails on peripherals whose 
YAML declare "additionalProperties: false" because the link to the 
feature domain controller bindings does not exist.

What would be your recommandation here as declaring:

patternProperties:
  "^.*@[0-9a-f]+$":
    description: Devices attached to system bus
    type: object
    properties:
      feature-domains:
        $ref: 
/schemas/feature-controllers/feature-domain-controller.yaml#/properties/feature-domains

does not solve the issue?



> > +          reg = <0x0 0x1000000>;
>
> Missing compatible, missing proper device name. Don't use fake names,
> but describe real case.

Linked to above issue.

> > +          feature-domains = <&etzpc 0>;
> > +        };
> > +
> > +        foo2: foo@2000000 {
> > +          reg = <0x0 0x2000000>;
> > +          feature-domains = <&etzpc 0>;
> > +        };
> > +    };
>
> Best regards,
> Krzysztof

Best regards,
Gatien