netdev - Re: [PATCH v8 net-next 06/10] net: dsa: microchip: add support for phylink management

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Date:   Mon, 7 Feb 2022 19:27:13 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Prasanna Vengateshan <prasanna.vengateshan@...rochip.com>
Cc:     andrew@...n.ch, netdev@...r.kernel.org, robh+dt@...nel.org,
        UNGLinuxDriver@...rochip.com, woojung.huh@...rochip.com,
        hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        kuba@...nel.org, linux-kernel@...r.kernel.org,
        vivien.didelot@...il.com, f.fainelli@...il.com,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v8 net-next 06/10] net: dsa: microchip: add support for
 phylink management

On Mon, Feb 07, 2022 at 10:52:00PM +0530, Prasanna Vengateshan wrote:
> +static void lan937x_apply_rgmii_delay(struct ksz_device *dev, int port,
> +				      phy_interface_t interface, u8 val)
> +{
> +	struct ksz_port *p = &dev->ports[port];
> +
> +	/* Clear Ingress & Egress internal delay enabled bits */
> +	val &= ~(PORT_RGMII_ID_EG_ENABLE | PORT_RGMII_ID_IG_ENABLE);
> +
> +	if (interface == PHY_INTERFACE_MODE_RGMII_TXID ||
> +	    interface == PHY_INTERFACE_MODE_RGMII_ID) {
> +		/* if the delay is 0, let us not enable DLL */
> +		if (p->rgmii_tx_val) {
> +			lan937x_update_rgmii_tx_rx_delay(dev, port, true);
> +			dev_info(dev->dev, "Applied rgmii tx delay for the port %d\n",
> +				 port);
> +			val |= PORT_RGMII_ID_EG_ENABLE;
> +		}
> +	}
> +
> +	if (interface == PHY_INTERFACE_MODE_RGMII_RXID ||
> +	    interface == PHY_INTERFACE_MODE_RGMII_ID) {
> +		/* if the delay is 0, let us not enable DLL */
> +		if (p->rgmii_rx_val) {
> +			lan937x_update_rgmii_tx_rx_delay(dev, port, false);
> +			dev_info(dev->dev, "Applied rgmii rx delay for the port %d\n",
> +				 port);
> +			val |= PORT_RGMII_ID_IG_ENABLE;
> +		}
> +	}
> +
> +	/* Enable RGMII internal delays */
> +	lan937x_pwrite8(dev, port, REG_PORT_XMII_CTRL_1, val);
> +}
> +
> +void lan937x_mac_config(struct ksz_device *dev, int port,
> +			phy_interface_t interface)
> +{
> +	u8 data8;
> +
> +	lan937x_pread8(dev, port, REG_PORT_XMII_CTRL_1, &data8);
> +
> +	/* clear MII selection & set it based on interface later */
> +	data8 &= ~PORT_MII_SEL_M;
> +
> +	/* configure MAC based on interface */
> +	switch (interface) {
> +	case PHY_INTERFACE_MODE_MII:
> +		lan937x_config_gbit(dev, false, &data8);
> +		data8 |= PORT_MII_SEL;
> +		break;
> +	case PHY_INTERFACE_MODE_RMII:
> +		lan937x_config_gbit(dev, false, &data8);
> +		data8 |= PORT_RMII_SEL;
> +		break;
> +	case PHY_INTERFACE_MODE_RGMII:
> +		lan937x_config_gbit(dev, true, &data8);
> +		data8 |= PORT_RGMII_SEL;
> +		break;
> +	case PHY_INTERFACE_MODE_RGMII_ID:
> +	case PHY_INTERFACE_MODE_RGMII_TXID:
> +	case PHY_INTERFACE_MODE_RGMII_RXID:
> +		lan937x_config_gbit(dev, true, &data8);
> +		data8 |= PORT_RGMII_SEL;
> +
> +		/* Apply rgmii internal delay for the mac */
> +		lan937x_apply_rgmii_delay(dev, port, interface, data8);

I think the agreement from previous discussions was to apply RGMII delay
_exclusively_ based on the 'rx-internal-delay-ps' and 'tx-internal-delay-ps'
properties, at least for new drivers with no legacy. You are omitting to
apply delays in phy-mode = "rgmii", which contradicts that agreement.
I think you should treat all 4 RGMII cases the same, and remove the
interface checks from lan937x_apply_rgmii_delay.

> +
> +		/* rgmii delay configuration is already applied above,
> +		 * hence return from here as no changes required
> +		 */
> +		return;
> +	default:
> +		dev_err(dev->dev, "Unsupported interface '%s' for port %d\n",
> +			phy_modes(interface), port);
> +		return;
> +	}
> +
> +	/* Write the updated value */
> +	lan937x_pwrite8(dev, port, REG_PORT_XMII_CTRL_1, data8);
> +}