linux-kernel - Re: [PATCH net-next 10/17] net: dsa: Introduce driver for NXP SJA1105 5-port L2 switch

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Message-ID: <20190402215522.GJ22349@lunn.ch>
Date:   Tue, 2 Apr 2019 23:55:22 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     f.fainelli@...il.com, vivien.didelot@...il.com,
        davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linus.walleij@...aro.org,
        georg.waibel@...sor-technik.de
Subject: Re: [PATCH net-next 10/17] net: dsa: Introduce driver for NXP
 SJA1105 5-port L2 switch

> +static int sja1105_init_mii_settings(struct sja1105_private *priv,
> +				     struct sja1105_dt_port *ports)
> +{
> +	struct device *dev = &priv->spidev->dev;
> +	struct sja1105_xmii_params_entry *mii;
> +	struct sja1105_table *table;
> +	int i;
> +
> +	table = &priv->static_config.tables[BLK_IDX_XMII_PARAMS];
> +
> +	/* Discard previous xMII Mode Parameters Table */
> +	if (table->entry_count) {
> +		kfree(table->entries);
> +		table->entry_count = 0;
> +	}
> +
> +	table->entries = kcalloc(MAX_XMII_PARAMS_COUNT,
> +				 table->ops->unpacked_entry_size, GFP_KERNEL);
> +	if (!table->entries)
> +		return -ENOMEM;
> +
> +	/* Override table based on phylib DT bindings */
> +	table->entry_count = MAX_XMII_PARAMS_COUNT;
> +
> +	mii = table->entries;
> +
> +	for (i = 0; i < SJA1105_NUM_PORTS; i++) {
> +		switch (ports[i].phy_mode) {
> +		case PHY_INTERFACE_MODE_MII:
> +			mii->xmii_mode[i] = XMII_MODE_MII;
> +			break;
> +		case PHY_INTERFACE_MODE_RMII:
> +			mii->xmii_mode[i] = XMII_MODE_RMII;
> +			break;
> +		case PHY_INTERFACE_MODE_RGMII:
> +		case PHY_INTERFACE_MODE_RGMII_ID:
> +		case PHY_INTERFACE_MODE_RGMII_RXID:
> +		case PHY_INTERFACE_MODE_RGMII_TXID:
> +			mii->xmii_mode[i] = XMII_MODE_RGMII;
> +			break;

https://www.nxp.com/docs/en/data-sheet/SJA1105.pdf

Section 6.2.3 RGMII signaling and encoding

Note that RGMII requires an external delay of between 1.5 ns and 2 ns
on TXC and RXC.

So it sounds like the switch only supports PHY_INTERFACE_MODE_RGMII.

If the port is in MAC mode, you should pass this phy-mode to the PHY
when you connect to it. The PHY can then add the delay if needed.

If however, the port is in PHY mode, and it is asked to do RGMII other
than PHY_INTERFACE_MODE_RGMII, you should report an error. It cannot
do it.

   Andrew