netdev - Re: [PATCH net-next v4 3/4] dt-bindings: dp83td510: Add binding for DP83TD510 Ethernet PHY

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Message-ID: <20201201001351.GA3297586@robh.at.kernel.org>
Date:   Mon, 30 Nov 2020 17:13:51 -0700
From:   Rob Herring <robh@...nel.org>
To:     Dan Murphy <dmurphy@...com>
Cc:     davem@...emloft.net, andrew@...n.ch, f.fainelli@...il.com,
        hkallweit1@...il.com, ciorneiioana@...il.com,
        devicetree@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v4 3/4] dt-bindings: dp83td510: Add binding for
 DP83TD510 Ethernet PHY

On Tue, Nov 17, 2020 at 02:15:54PM -0600, Dan Murphy wrote:
> The DP83TD510 is a 10M single twisted pair Ethernet PHY
> 
> Signed-off-by: Dan Murphy <dmurphy@...com>
> ---
>  .../devicetree/bindings/net/ti,dp83td510.yaml | 64 +++++++++++++++++++
>  1 file changed, 64 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/net/ti,dp83td510.yaml
> 
> diff --git a/Documentation/devicetree/bindings/net/ti,dp83td510.yaml b/Documentation/devicetree/bindings/net/ti,dp83td510.yaml
> new file mode 100644
> index 000000000000..d3c97bb4d820
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/net/ti,dp83td510.yaml
> @@ -0,0 +1,64 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +# Copyright (C) 2020 Texas Instruments Incorporated
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/net/ti,dp83td510.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: TI DP83TD510 ethernet PHY
> +
> +allOf:
> +  - $ref: "ethernet-controller.yaml#"
> +  - $ref: "ethernet-phy.yaml#"
> +
> +maintainers:
> +  - Dan Murphy <dmurphy@...com>
> +
> +description: |
> +  The PHY is an twisted pair 10Mbps Ethernet PHY that support MII, RMII and
> +  RGMII interfaces.
> +
> +  Specifications about the Ethernet PHY can be found at:
> +    http://www.ti.com/lit/ds/symlink/dp83td510e.pdf
> +
> +properties:
> +  reg:
> +    maxItems: 1
> +
> +  tx-fifo-depth:
> +    description: |
> +       Transmitt FIFO depth for RMII mode.  The PHY only exposes 4 nibble
> +       depths. The valid nibble depths are 4, 5, 6 and 8.
> +    enum: [ 4, 5, 6, 8 ]
> +    default: 5
> +
> +  rx-internal-delay-ps:
> +    description: |
> +       Setting this property to a non-zero number sets the RX internal delay
> +       for the PHY.  The internal delay for the PHY is fixed to 30ns relative
> +       to receive data.

I'm confused. The delay is 30ns +/- whatever is set here?

> +
> +  tx-internal-delay-ps:
> +    description: |
> +       Setting this property to a non-zero number sets the TX internal delay
> +       for the PHY.  The internal delay for the PHY has a range of -4 to 4ns
> +       relative to transmit data.

Sounds like constraints?

We do have a problem handling negative values though. Addressing in dtc 
was rejected, so we'll need to fixup the schema with unsigned values. 
But here it should just be negative values.

> +
> +unevaluatedProperties: false
> +
> +required:
> +  - reg
> +
> +examples:
> +  - |
> +    mdio0 {
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +      ethphy0: ethernet-phy@0 {
> +        reg = <0>;
> +        tx-rx-output-high;
> +        tx-fifo-depth = <5>;
> +        rx-internal-delay-ps = <1>;
> +        tx-internal-delay-ps = <1>;
> +      };
> +    };
> -- 
> 2.29.2
>