Message-Id: <20250410115302.2562562-4-o.rempel@pengutronix.de>
Date: Thu, 10 Apr 2025 13:52:53 +0200
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Woojung Huh <woojung.huh@...rochip.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Russell King <rmk+kernel@...linux.org.uk>,
	Thangaraj Samynathan <Thangaraj.S@...rochip.com>,
	Rengarajan Sundararajan <Rengarajan.S@...rochip.com>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>,
	kernel@...gutronix.de,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	UNGLinuxDriver@...rochip.com,
	Phil Elwell <phil@...pberrypi.org>,
	Maxime Chevallier <maxime.chevallier@...tlin.com>,
	Simon Horman <horms@...nel.org>
Subject: [PATCH net-next v6 03/12] net: usb: lan78xx: refactor PHY init to separate detection and MAC configuration

Split out PHY detection into lan78xx_get_phy() and MAC-side setup into
lan78xx_mac_prepare_for_phy(), making the main lan78xx_phy_init() cleaner
and easier to follow.

This improves separation of concerns and prepares the code for a future
transition to phylink. Fixed PHY registration and interface selection
are now handled in lan78xx_get_phy(), while MAC-side delay configuration
is done in lan78xx_mac_prepare_for_phy().

The fixed PHY fallback is preserved for setups like EVB-KSZ9897-1,
where LAN7801 connects directly to a KSZ switch without a standard PHY
or device tree support.

No functional changes intended.

Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
---
changes v6:
- this patch is added in v6
---
 drivers/net/usb/lan78xx.c | 174 ++++++++++++++++++++++++++++----------
 1 file changed, 128 insertions(+), 46 deletions(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 2876a119159c..a54d246244b8 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -2508,53 +2508,145 @@ static void lan78xx_remove_irq_domain(struct lan78xx_net *dev)
 	dev->domain_data.irqdomain = NULL;
 }
 
-static struct phy_device *lan7801_phy_init(struct lan78xx_net *dev)
+/**
+ * lan78xx_register_fixed_phy() - Register a fallback fixed PHY
+ * @dev: LAN78xx device
+ *
+ * Registers a fixed PHY with 1 Gbps full duplex. This is used in special cases
+ * like EVB-KSZ9897-1, where LAN7801 acts as a USB-to-Ethernet interface to a
+ * switch without a visible PHY.
+ *
+ * Return: pointer to the registered fixed PHY, or ERR_PTR() on error.
+ */
+static struct phy_device *lan78xx_register_fixed_phy(struct lan78xx_net *dev)
 {
 	struct fixed_phy_status fphy_status = {
 		.link = 1,
 		.speed = SPEED_1000,
 		.duplex = DUPLEX_FULL,
 	};
+
+	netdev_info(dev->net,
+		    "No PHY found on LAN7801 – registering fixed PHY (e.g. EVB-KSZ9897-1)\n");
+
+	return fixed_phy_register(PHY_POLL, &fphy_status, NULL);
+}
+
+/**
+ * lan78xx_get_phy() - Probe or register PHY device and set interface mode
+ * @dev: LAN78xx device structure
+ *
+ * This function attempts to find a PHY on the MDIO bus. If no PHY is found
+ * and the chip is LAN7801, it registers a fixed PHY as fallback. It also
+ * sets dev->interface based on chip ID and detected PHY type.
+ *
+ * Return: a valid PHY device pointer, or ERR_PTR() on failure.
+ */
+static struct phy_device *lan78xx_get_phy(struct lan78xx_net *dev)
+{
 	struct phy_device *phydev;
-	int ret;
 
+	/* Attempt to locate a PHY on the MDIO bus */
 	phydev = phy_find_first(dev->mdiobus);
-	if (!phydev) {
-		netdev_dbg(dev->net, "PHY Not Found!! Registering Fixed PHY\n");
-		phydev = fixed_phy_register(PHY_POLL, &fphy_status, NULL);
-		if (IS_ERR(phydev)) {
-			netdev_err(dev->net, "No PHY/fixed_PHY found\n");
-			return ERR_PTR(-ENODEV);
+
+	switch (dev->chipid) {
+	case ID_REV_CHIP_ID_7801_:
+		if (phydev) {
+			/* External RGMII PHY detected */
+			dev->interface = PHY_INTERFACE_MODE_RGMII_ID;
+			phydev->is_internal = false;
+
+			if (!phydev->drv)
+				netdev_warn(dev->net,
+					    "PHY driver not found – assuming RGMII delays are on PCB or strapped for the PHY\n");
+
+			return phydev;
 		}
-		netdev_dbg(dev->net, "Registered FIXED PHY\n");
+
 		dev->interface = PHY_INTERFACE_MODE_RGMII;
+		/* No PHY found – fallback to fixed PHY (e.g. KSZ switch board) */
+		return lan78xx_register_fixed_phy(dev);
+
+	case ID_REV_CHIP_ID_7800_:
+	case ID_REV_CHIP_ID_7850_:
+		if (!phydev)
+			return ERR_PTR(-ENODEV);
+
+		/* These use internal GMII-connected PHY */
+		dev->interface = PHY_INTERFACE_MODE_GMII;
+		phydev->is_internal = true;
+		return phydev;
+
+	default:
+		netdev_err(dev->net, "Unknown CHIP ID: 0x%08x\n", dev->chipid);
+		return ERR_PTR(-ENODEV);
+	}
+}
+
+/**
+ * lan78xx_mac_prepare_for_phy() - Preconfigure MAC-side interface settings
+ * @dev: LAN78xx device
+ *
+ * Configure MAC-side registers according to dev->interface, which should be
+ * set by lan78xx_get_phy().
+ *
+ * - For PHY_INTERFACE_MODE_RGMII:
+ *   Enable MAC-side TXC delay. This mode seems to be used in a special setup
+ *   without a real PHY, likely on EVB-KSZ9897-1. In that design, LAN7801 is
+ *   connected to the KSZ9897 switch, and the link timing is expected to be
+ *   hardwired (e.g. via strapping or board layout). No devicetree support is
+ *   assumed here.
+ *
+ * - For PHY_INTERFACE_MODE_RGMII_ID:
+ *   Disable MAC-side delay and rely on the PHY driver to provide delay.
+ *
+ * - For GMII, no MAC-specific config is needed.
+ *
+ * Return: 0 on success or a negative error code.
+ */
+static int lan78xx_mac_prepare_for_phy(struct lan78xx_net *dev)
+{
+	int ret;
+
+	switch (dev->interface) {
+	case PHY_INTERFACE_MODE_RGMII:
+		/* Enable MAC-side TX clock delay */
 		ret = lan78xx_write_reg(dev, MAC_RGMII_ID,
 					MAC_RGMII_ID_TXC_DELAY_EN_);
 		if (ret < 0)
-			return ERR_PTR(ret);
+			return ret;
 
 		ret = lan78xx_write_reg(dev, RGMII_TX_BYP_DLL, 0x3D00);
 		if (ret < 0)
-			return ERR_PTR(ret);
+			return ret;
 
-		ret = lan78xx_update_reg(dev, HW_CFG, HW_CFG_CLK125_EN_ |
-					 HW_CFG_REFCLK25_EN_,
+		ret = lan78xx_update_reg(dev, HW_CFG,
+					 HW_CFG_CLK125_EN_ | HW_CFG_REFCLK25_EN_,
 					 HW_CFG_CLK125_EN_ | HW_CFG_REFCLK25_EN_);
 		if (ret < 0)
-			return ERR_PTR(ret);
-	} else {
-		dev->interface = PHY_INTERFACE_MODE_RGMII_ID;
-		/* The PHY driver is responsible to configure proper RGMII
-		 * interface delays. Disable RGMII delays on MAC side.
-		 */
+			return ret;
+
+		break;
+
+	case PHY_INTERFACE_MODE_RGMII_ID:
+		/* Disable MAC-side TXC delay, PHY provides it */
 		ret = lan78xx_write_reg(dev, MAC_RGMII_ID, 0);
 		if (ret < 0)
-			return ERR_PTR(ret);
+			return ret;
 
-		phydev->is_internal = false;
+		break;
+
+	case PHY_INTERFACE_MODE_GMII:
+		/* No MAC-specific configuration required */
+		break;
+
+	default:
+		netdev_warn(dev->net, "Unsupported interface mode: %d\n",
+			    dev->interface);
+		break;
 	}
 
-	return phydev;
+	return 0;
 }
 
 static int lan78xx_phy_init(struct lan78xx_net *dev)
@@ -2564,31 +2656,13 @@ static int lan78xx_phy_init(struct lan78xx_net *dev)
 	u32 mii_adv;
 	struct phy_device *phydev;
 
-	switch (dev->chipid) {
-	case ID_REV_CHIP_ID_7801_:
-		phydev = lan7801_phy_init(dev);
-		if (IS_ERR(phydev)) {
-			netdev_err(dev->net, "lan7801: failed to init PHY: %pe\n",
-				   phydev);
-			return PTR_ERR(phydev);
-		}
-		break;
-
-	case ID_REV_CHIP_ID_7800_:
-	case ID_REV_CHIP_ID_7850_:
-		phydev = phy_find_first(dev->mdiobus);
-		if (!phydev) {
-			netdev_err(dev->net, "no PHY found\n");
-			return -ENODEV;
-		}
-		phydev->is_internal = true;
-		dev->interface = PHY_INTERFACE_MODE_GMII;
-		break;
+	phydev = lan78xx_get_phy(dev);
+	if (IS_ERR(phydev))
+		return PTR_ERR(phydev);
 
-	default:
-		netdev_err(dev->net, "Unknown CHIP ID found\n");
-		return -ENODEV;
-	}
+	ret = lan78xx_mac_prepare_for_phy(dev);
+	if (ret < 0)
+		goto free_phy;
 
 	/* if phyirq is not set, use polling mode in phylib */
 	if (dev->domain_data.phyirq > 0)
@@ -2662,6 +2736,14 @@ static int lan78xx_phy_init(struct lan78xx_net *dev)
 	dev->fc_autoneg = phydev->autoneg;
 
 	return 0;
+
+free_phy:
+	if (phy_is_pseudo_fixed_link(phydev)) {
+		fixed_phy_unregister(phydev);
+		phy_device_free(phydev);
+	}
+
+	return ret;
 }
 
 static int lan78xx_set_rx_max_frame_length(struct lan78xx_net *dev, int size)
-- 
2.39.5

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