netdev - Re: [PATCH v2 2/3] dt-bindings: can: ctucanfd: add another clock for HW timestamping

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Date:   Wed, 3 Aug 2022 00:41:46 +0200
From:   Matej Vasilevski <matej.vasilevski@...nam.cz>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Pavel Pisa <pisa@....felk.cvut.cz>,
        Ondrej Ille <ondrej.ille@...il.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/3] dt-bindings: can: ctucanfd: add another clock for
 HW timestamping

On Tue, Aug 02, 2022 at 09:49:03AM +0200, Krzysztof Kozlowski wrote:
> On 01/08/2022 20:46, Matej Vasilevski wrote:
> > Add second clock phandle to specify the timestamping clock.
> > You can even use the same clock as the core, or define a fixed-clock
> > if you need something custom.
> > 
> > Signed-off-by: Matej Vasilevski <matej.vasilevski@...nam.cz>
> > ---
> >  .../bindings/net/can/ctu,ctucanfd.yaml        | 23 +++++++++++++++----
> >  1 file changed, 19 insertions(+), 4 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/net/can/ctu,ctucanfd.yaml b/Documentation/devicetree/bindings/net/can/ctu,ctucanfd.yaml
> > index 4635cb96fc64..90390530f909 100644
> > --- a/Documentation/devicetree/bindings/net/can/ctu,ctucanfd.yaml
> > +++ b/Documentation/devicetree/bindings/net/can/ctu,ctucanfd.yaml
> > @@ -44,9 +44,23 @@ properties:
> >  
> >    clocks:
> >      description: |
> > -      phandle of reference clock (100 MHz is appropriate
> > -      for FPGA implementation on Zynq-7000 system).
> > -    maxItems: 1
> > +      Phandle of reference clock (100 MHz is appropriate for FPGA
> > +      implementation on Zynq-7000 system). If you wish to use timestamps
> > +      from the controller, add a second phandle with the clock used for
> > +      timestamping. The timestamping clock is optional, if you don't
> > +      add it here, the driver will use the primary clock frequency for
> > +      timestamp calculations. If you need something custom, define
> > +      a fixed-clock oscillator and reference it.
> 
> This should not be a guide how to write DTS, but description of
> hardware. The references to driver are also not really appropriate in
> the bindings (are you 100% sure that all other operating systems and SW
> have driver which behaves like this...)
> 

Hello Krzysztof,

thanks for your comment. I'll rewrite it so that it only describes
the hardware.

Best regards,
Matej

> > +    minItems: 1
> > +    items:
> > +      - description: core clock
> > +      - description: timestamping clock
> > +
> > +  clock-names:
> > +    minItems: 1
> > +    items:
> > +      - const: core-clk
> > +      - const: ts-clk
> >  
> >  required:
> >    - compatible
> > @@ -61,6 +75,7 @@ examples:
> >      ctu_can_fd_0: can@...30000 {
> >        compatible = "ctu,ctucanfd";
> >        interrupts = <0 30 4>;
> > -      clocks = <&clkc 15>;
> > +      clocks = <&clkc 15>, <&clkc 16>;
> > +      clock-names = "core-clk", "ts-clk";
> >        reg = <0x43c30000 0x10000>;
> >      };
> 
> 
> Best regards,
> Krzysztof