netdev - Re: [RFC PATCH 2/3] dt-bindings: can: ctucanfd: add properties for HW timestamping

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Message-ID: <20220516160250.GA2724701-robh@kernel.org>
Date:   Mon, 16 May 2022 11:02:50 -0500
From:   Rob Herring <robh@...nel.org>
To:     Matej Vasilevski <matej.vasilevski@...nam.cz>
Cc:     linux-can@...r.kernel.org, mkl@...gutronix.de,
        pisa@....felk.cvut.cz, devicetree@...r.kernel.org,
        netdev@...r.kernel.org, ondrej.ille@...il.com,
        martin.jerabek01@...il.com
Subject: Re: [RFC PATCH 2/3] dt-bindings: can: ctucanfd: add properties for
 HW timestamping

On Fri, May 13, 2022 at 01:27:06AM +0200, Matej Vasilevski wrote:
> Extend dt-bindings for CTU CAN-FD IP core with necessary properties
> to enable HW timestamping for platform devices. Since the timestamping
> counter is provided by the system integrator usign those IP cores in
> their FPGA design, we need to have the properties specified in device tree.
> 
> Signed-off-by: Matej Vasilevski <matej.vasilevski@...nam.cz>
> ---
>  .../bindings/net/can/ctu,ctucanfd.yaml        | 34 +++++++++++++++++--
>  1 file changed, 31 insertions(+), 3 deletions(-)

What's the base for this patch? Doesn't apply for me.

> 
> diff --git a/Documentation/devicetree/bindings/net/can/ctu,ctucanfd.yaml b/Documentation/devicetree/bindings/net/can/ctu,ctucanfd.yaml
> index fb34d971dcb3..c3693dadbcd8 100644
> --- a/Documentation/devicetree/bindings/net/can/ctu,ctucanfd.yaml
> +++ b/Documentation/devicetree/bindings/net/can/ctu,ctucanfd.yaml
> @@ -41,9 +41,35 @@ properties:
>  
>    clocks:
>      description: |
> -      phandle of reference clock (100 MHz is appropriate
> -      for FPGA implementation on Zynq-7000 system).
> +      Phandle of reference clock (100 MHz is appropriate for FPGA
> +      implementation on Zynq-7000 system). If you wish to use timestamps
> +      from the core, add a second phandle with the clock used for timestamping
> +      (can be the same as the first clock).
> +    maxItems: 2

With more than 1, you have to define what each entry is. IOW, use 
'items'.

> +
> +  clock-names:
> +    description: |
> +      Specify clock names for the "clocks" property. The first clock name
> +      doesn't matter, the second has to be "ts_clk". Timestamping frequency
> +      is then obtained from the "ts_clk" clock. This takes precedence over
> +      the ts-frequency property.
> +      You can omit this property if you don't need timestamps.
> +    maxItems: 2

You must define what the names are as a schema.

> +
> +  ts-used-bits:
> +    description: width of the timestamping counter
> +    maxItems: 1
> +    items:

Not an array, so you don't need maxItems nor items.

> +      minimum: 8
> +      maximum: 64
> +
> +  ts-frequency:

Use a standard unit suffix.

> +    description: |
> +      Frequency of the timestamping counter. Set this if you want to get
> +      timestamps, but you didn't set the timestamping clock in clocks property.
>      maxItems: 1
> +    items:

Not an array.


Is timestamping a common feature for CAN or is this specific to this 
controller? In the latter case, you need vendor prefixes on these 
properties. In the former case, you need to define them in a common 
schema.

> +      minimum: 1
>  
>  required:
>    - compatible
> @@ -58,6 +84,8 @@ examples:
>      ctu_can_fd_0: can@...30000 {
>        compatible = "ctu,ctucanfd";
>        interrupts = <0 30 4>;
> -      clocks = <&clkc 15>;
> +      clocks = <&clkc 15>, <&clkc 15>;
> +      clock-names = "can_clk", "ts_clk";
>        reg = <0x43c30000 0x10000>;
> +      ts-used-bits = <64>;
>      };
> -- 
> 2.25.1
> 
>