Re: [PATCH v3 2/3] dt-binding: net: sfp binding documentation

Russell King - ARM Linux
2017-09-03T20:46:54Z

On Sun, Sep 03, 2017 at 03:31:13PM +0300, Baruch Siach wrote:
> Add device-tree binding documentation SFP transceivers. Support for SFP
> transceivers has been recently introduced (drivers/net/phy/sfp.c).
>
> Signed-off-by: Baruch Siach <baruch@tkos.co.il>
> ---
> v3:
> Mention gpios phandle and specifier
> Mention the polarity of each gpio
> Fix example property names
>
> v2:
> Rename -gpio properties to -gpios
> Rename the rate-select-gpio property to rate-select0-gpios
> Add the rate-select1-gpios property
> Add examples
> ---
> Documentation/devicetree/bindings/net/sff,sfp.txt | 78 +++++++++++++++++++++++
> 1 file changed, 78 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/net/sff,sfp.txt
>
> diff --git a/Documentation/devicetree/bindings/net/sff,sfp.txt b/Documentation/devicetree/bindings/net/sff,sfp.txt
> new file mode 100644
> index 000000000000..b98ee5945265
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/net/sff,sfp.txt
> @@ -0,0 +1,78 @@
> +Small Form Factor (SFF) Committee Small Form-factor Pluggable (SFP)
> +Transceiver
> +
> +Required properties:
> +
> +- compatible : must be "sff,sfp"
> +
> +Optional Properties:
> +
> +- i2c-bus : phandle of an I2C bus controller for the SFP two wire serial
> + interface
> +
> +- moddef0-gpios : GPIO phandle and a single specifier of the MOD-DEF0 (AKA
> + Mod_ABS) module presence input gpio signal, active (module absent) high
> +
> +- los-gpios : GPIO phandle and a single specifier of the Receiver Loss of
> + Signal Indication input gpio signal, active (signal lost) high
> +
> +- tx-fault-gpios : GPIO phandle and a single specifier of the Module
> + Transmitter Fault input gpio signal, active (fault condition) high
> +
> +- tx-disable-gpios : GPIO phandle and a single specifier of the Transmitter
> + Disable output gpio signal, active (Tx disable) high
> +
> +- rate-select0-gpios : GPIO phandle and a single specifier of the Rx Signaling
> + Rate Select (AKA RS0) output gpio signal, low: low Rx rate, high: high Rx
> + rate
> +
> +- rate-select1-gpios : GPIO phandle and a single specifier of the Tx Signaling
> + Rate Select (AKA RS1) output gpio signal (SFP+ only), low: low Tx rate,
> + high: high Tx rate
> +
> +Example #1: Direct serdes to SFP connection
> +
> +sfp_eth3: sfp-eth3 {
> + compatible = "sff,sfp";
> + i2c-bus = <&sfp_1g_i2c>;
> + los-gpios = <&cpm_gpio2 22 GPIO_ACTIVE_HIGH>;
> + moddef0-gpios = <&cpm_gpio2 21 GPIO_ACTIVE_LOW>;
> + pinctrl-names = "default";
> + pinctrl-0 = <&cpm_sfp_1g_pins &cps_sfp_1g_pins>;
> + tx-disable-gpios = <&cps_gpio1 24 GPIO_ACTIVE_HIGH>;
> + tx-fault-gpios = <&cpm_gpio2 19 GPIO_ACTIVE_HIGH>;
> +};
> +
> +&cps_emac3 {
> + phy-mode = "sgmii";
> + phy-names = "comphy";
> + phys = <&cps_comphy 5 COMPHY_SGMII2>;

I don't like this level of example - SGMII is Cisco SGMII which is not
the same as 1000Base-X - the two are incompatible. Fibre SFP modules
only work with 1000Base-X.

The SFP/phylink takes care of informing the MAC which mode it should
be in, and the MAC must configure itself appropriately in response to
that, otherwise the module can't be supported.

--
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