linux-kernel - Re: [PATCH net-next v1 1/3] dt-bindings: net: Add Motorcomm yt8xxx ethernet phy Driver bindings

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Message-ID: <Y7bN4vJXMi66FF6v@lunn.ch>
Date:   Thu, 5 Jan 2023 14:17:22 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Frank <Frank.Sae@...or-comm.com>
Cc:     Peter Geis <pgwipeout@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "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>,
        xiaogang.fan@...or-comm.com, fei.zhang@...or-comm.com,
        hua.sun@...or-comm.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH net-next v1 1/3] dt-bindings: net: Add Motorcomm yt8xxx
 ethernet phy Driver bindings

> +  motorcomm,rx-delay-basic:
> +    description: |
> +      Tristate, setup the basic RGMII RX Clock delay of PHY.
> +      This basic delay is fixed at 2ns (1000Mbps) or 8ns (100Mbps、10Mbps).
> +      This basic delay usually auto set by hardware according to the voltage
> +      of RXD0 pin (low = 0, turn off;   high = 1, turn on).
> +      If not exist, this delay is controlled by hardware.
> +      0: turn off;   1: turn on.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    enum: [0, 1]

Why is this needed? When the MAC driver connects to the PHY, it passes
phy-mode. For RGMII, this is one of:

linux/phy.h:	PHY_INTERFACE_MODE_RGMII,
linux/phy.h:	PHY_INTERFACE_MODE_RGMII_ID,
linux/phy.h:	PHY_INTERFACE_MODE_RGMII_RXID,
linux/phy.h:	PHY_INTERFACE_MODE_RGMII_TXID,

This tells you if you need to add a delay for the RX clock line, the
TX clock line, or both. That is all you need to know for basic RGMII
delays.

> +  motorcomm,rx-delay-additional-ps:

ethernet-phy.yaml defines rx-internal-delay-ps. Please use that.

> +    description: |
> +      Setup the additional RGMII RX Clock delay of PHY defined in pico seconds.
> +      RGMII RX Clock Delay = rx-delay-basic + rx-delay-additional-ps.
> +    enum:
> +      - 0
> +      - 150
> +      - 300
> +      - 450
> +      - 600
> +      - 750
> +      - 900
> +      - 1050
> +      - 1200
> +      - 1350
> +      - 1500
> +      - 1650
> +      - 1800
> +      - 1950
> +      - 2100
> +      - 2250

Is this property mandatory? If not, please document what value is used
if it is not present.

> +
> +  motorcomm,tx-delay-ge-ps:

tx-internal-delay-ps

And please define the default.

> +  motorcomm,tx-delay-fe-ps:

So you can only set the TX delay? What is RX delay set to? Same as 1G?
I would suggest you call this motorcomm,tx-internal-delay-fe-ps, so
that it is similar to the standard tx-internal-delay-ps.

> +    description: |
> +      Setup PHY's RGMII TX Clock delay  defined in pico seconds when the speed
> +      is 100Mbps or 10Mbps.
> +    enum:
> +      - 0
> +      - 150
> +      - 300
> +      - 450
> +      - 600
> +      - 750
> +      - 900
> +      - 1050
> +      - 1200
> +      - 1350
> +      - 1500
> +      - 1650
> +      - 1800
> +      - 1950
> +      - 2100
> +      - 2250
> +
> +  motorcomm,keep-pll-enabled:
> +    description: |
> +      If set, keep the PLL enabled even if there is no link. Useful if you
> +      want to use the clock output without an ethernet link.
> +    type: boolean
> +
> +  motorcomm,auto-sleep-disabled:
> +    description: |
> +      If set, PHY will not enter sleep mode and close AFE after unplug cable
> +      for a timer.
> +    type: boolean

These two i can see being useful. But everything afterwards seems like
just copy/paste from vendor SDK for things which the hardware can do,
but probably nobody ever uses. Do you have a board using any of the
following properties?

> +
> +  motorcomm,tx-clk-adj-enabled:
> +    description: |
> +      Useful if you want to use tx-clk-xxxx-inverted to adj the delay of tx clk.
> +    type: boolean
> +
> +  motorcomm,tx-clk-10-inverted:
> +    description: |
> +      Use original or inverted RGMII Transmit PHY Clock to drive the RGMII
> +      Transmit PHY Clock delay train configuration when speed is 10Mbps.
> +    type: boolean
> +
> +  motorcomm,tx-clk-100-inverted:
> +    description: |
> +      Use original or inverted RGMII Transmit PHY Clock to drive the RGMII
> +      Transmit PHY Clock delay train configuration when speed is 100Mbps.
> +    type: boolean
> +
> +  motorcomm,tx-clk-1000-inverted:
> +    description: |
> +      Use original or inverted RGMII Transmit PHY Clock to drive the RGMII
> +      Transmit PHY Clock delay train configuration when speed is 1000Mbps.
> +    type: boolean
> +
> +  motorcomm,sds-tx-amplitude:
> +    description: |
> +      Setup the tx driver amplitude control of SerDes. Higher amplitude is
> +      helpful for long distance.
> +      0: low;   1: middle;   2: high.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    enum: [0, 1, 2]
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    ethernet {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        ethernet-phy@5 {
> +            reg = <5>;

PHYs are on MDIO busses, so i would expect to see an MDIO bus here,
not Ethernet.

    Andrew