linux-kernel - Re: [PATCH net-next] net: phy: intel-xway: Add RGMII internal delay configuration

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Date:   Fri, 9 Jul 2021 15:33:01 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Martin Schiller <ms@....tdt.de>
Cc:     hauke@...ke-m.de, martin.blumenstingl@...glemail.com,
        f.fainelli@...il.com, hkallweit1@...il.com, linux@...linux.org.uk,
        davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: phy: intel-xway: Add RGMII internal delay
 configuration

> +	/* RX delay *must* be specified if internal delay of RX is used. */
> +	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
> +	    phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID) {
> +		rx_int_delay = phy_get_internal_delay(phydev, dev,
> +						      &xway_internal_delay[0],
> +						      delay_size, true);
> +
> +		if (rx_int_delay < 0) {
> +			phydev_err(phydev, "rx-internal-delay-ps must be specified\n");
> +			return rx_int_delay;
> +		}
> +
> +		val &= ~XWAY_MDIO_MIICTRL_RXSKEW_MASK;
> +		val |= rx_int_delay << XWAY_MDIO_MIICTRL_RXSKEW_SHIFT;
> +	}

Please don't force the delay property to be present, use the default
of 2ns if it is missing.

> +	if (phydev->interface == PHY_INTERFACE_MODE_RGMII_ID ||
> +	    phydev->interface == PHY_INTERFACE_MODE_RGMII_RXID ||
> +	    phydev->interface == PHY_INTERFACE_MODE_RGMII_TXID)
> +		err = phy_write(phydev, XWAY_MDIO_MIICTRL, val);
> +

This is the tricky bit. Do we want to act on PHY_INTERFACE_MODE_RGMII?
At the moment, i would say no, lets see how many patches we get
because of the warning you add. But i think it is worth adding a
comment here, briefly explaining why it is missing.

	Andrew