Re: [RFC PATCH 1/4] dt-bindings: net: can: add STM32 bxcan DT bindings

[Dario Binacchi <dario.binacchi@amarulasolutions.com>]

Hi Krzysztof,

On Thu, Aug 18, 2022 at 10:22 AM Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> On 17/08/2022 17:35, Dario Binacchi wrote:
> > Add documentation of device tree bindings for the STM32 basic extended
> > CAN (bxcan) controller.
> >
> > Signed-off-by: Dario Binacchi <dariobin@libero.it>
> > Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
>
> You do not need two SoBs. Keep only one, matching the From field.

I started implementing this driver in my spare time, so my intention
was to keep track of it.

>
> > ---
> >
> >  .../devicetree/bindings/net/can/st,bxcan.yaml | 139 ++++++++++++++++++
> >  1 file changed, 139 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/net/can/st,bxcan.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/net/can/st,bxcan.yaml b/Documentation/devicetree/bindings/net/can/st,bxcan.yaml
> > new file mode 100644
> > index 000000000000..f4cfd26e4785
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/net/can/st,bxcan.yaml
>
> File name like compatible, so st,stm32-bxcan-core.yaml (or some other
> name, see comment later)

>
> > @@ -0,0 +1,139 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/net/can/st,bxcan.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: STMicroelectronics bxCAN controller Device Tree Bindings
>
> s/Device Tree Bindings//

>
> > +
> > +description: STMicroelectronics BxCAN controller for CAN bus
> > +
> > +maintainers:
> > +  - Dario Binacchi <dario.binacchi@amarulasolutions.com>
> > +
> > +allOf:
> > +  - $ref: can-controller.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - st,stm32-bxcan-core
>
> compatibles are supposed to be specific. If this is some type of
> micro-SoC, then it should have its name/number. If it is dedicated
> device, is the final name bxcan core? Google says  the first is true, so
> you miss specific device part.

I don't know if I understand correctly, I hope the change in version 2
is what you requested.

>
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  resets:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    description:
> > +      Input clock for registers access
> > +    maxItems: 1
> > +
> > +  '#address-cells':
> > +    const: 1
> > +
> > +  '#size-cells':
> > +    const: 0
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - resets
> > +  - clocks
> > +  - '#address-cells'
> > +  - '#size-cells'
> > +
> > +additionalProperties: false
> > +
> > +patternProperties:
>
> This goes after "properties: in top level (before "required").
>
> > +  "^can@[0-9]+$":
> > +    type: object
> > +    description:
> > +      A CAN block node contains two subnodes, representing each one a CAN
> > +      instance available on the machine.
> > +
> > +    properties:
> > +      compatible:
> > +        enum:
> > +          - st,stm32-bxcan
>
> Why exactly do you need compatible for the child? Is it an entierly
> separate device?

I took inspiration from other drivers for ST microcontroller
peripherals (e. g. drivers/iio/adc/stm32-adc-core.c,
drivers/iio/adc/stm32-adc.c) where
some resources are shared between the peripheral instances. In the
case of CAN, master (CAN1) and slave (CAN2) share the registers for
configuring the filters and the clock.
In the core module you can find the functions about the shared
resources, while the childrens implement the driver.

>
> Comments about specific part are applied here as well.
>
> > +
> > +      master:
>
> Is this a standard property?

no

> I don't see it anywhere else. Non-standard
> properties require vendor prefix.

ok, you'll find it in V2.

Thanks and regards,
Dario

>
> > +        description:
> > +          Master and slave mode of the bxCAN peripheral is only relevant
> > +          if the chip has two CAN peripherals. In that case they share
> > +          some of the required logic, and that means you cannot use the
> > +          slave CAN without the master CAN.
> > +        type: boolean
> > +
> > +      reg:
> > +        description: |
> > +          Offset of CAN instance in CAN block. Valid values are:
> > +            - 0x0:   CAN1
> > +            - 0x400: CAN2
> > +        maxItems: 1
> > +
> > +      interrupts:
> > +        items:
> > +          - description: transmit interrupt
> > +          - description: FIFO 0 receive interrupt
> > +          - description: FIFO 1 receive interrupt
> > +          - description: status change error interrupt
> > +
> > +      interrupt-names:
> > +        items:
> > +          - const: tx
> > +          - const: rx0
> > +          - const: rx1
> > +          - const: sce
> > +
> > +      resets:
> > +        maxItems: 1
> > +
> > +      clocks:
> > +        description:
> > +          Input clock for registers access
> > +        maxItems: 1
> > +
> > +    additionalProperties: false
> > +
> > +    required:
> > +      - compatible
> > +      - reg
> > +      - interrupts
> > +      - resets
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/clock/stm32fx-clock.h>
> > +    #include <dt-bindings/mfd/stm32f4-rcc.h>
> > +
> > +    can: can@40006400 {
> > +        compatible = "st,stm32-bxcan-core";
> > +        reg = <0x40006400 0x800>;
> > +        resets = <&rcc STM32F4_APB1_RESET(CAN1)>;
> > +        clocks = <&rcc 0 STM32F4_APB1_CLOCK(CAN1)>;
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +        status = "disabled";
>
> No status in examples.
>
> > +
> > +        can1: can@0 {
> > +            compatible = "st,stm32-bxcan";
> > +            reg = <0x0>;
> > +            interrupts = <19>, <20>, <21>, <22>;
> > +            interrupt-names = "tx", "rx0", "rx1", "sce";
> > +            resets = <&rcc STM32F4_APB1_RESET(CAN1)>;
> > +            master;
> > +            status = "disabled";
>
> No status in examples.
>
>
> > +        };
> > +
> > +        can2: can@400 {
> > +            compatible = "st,stm32-bxcan";
> > +            reg = <0x400>;
> > +            interrupts = <63>, <64>, <65>, <66>;
> > +            interrupt-names = "tx", "rx0", "rx1", "sce";
> > +            resets = <&rcc STM32F4_APB1_RESET(CAN2)>;
> > +            clocks = <&rcc 0 STM32F4_APB1_CLOCK(CAN2)>;
> > +            status = "disabled";
>
> No status in examples.
>
> > +        };
> > +    };
>
>
> Best regards,
> Krzysztof



-- 

Dario Binacchi

Embedded Linux Developer

dario.binacchi@amarulasolutions.com

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