From 68502f802a66b68a6b5fefb52e709807a702a94b Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Mon, 26 Nov 2018 19:46:58 +0000
Subject: [PATCH 443/454] net: lan78xx: Support auto-downshift to 100Mb/s

Ethernet cables with faulty or missing pairs (specifically pairs C and
D) allow auto-negotiation to 1000Mbs, but do not support the successful
establishment of a link. Add a DT property, "microchip,downshift-after",
to configure the number of auto-negotiation failures after which it
falls back to 100Mbs. Valid values are 2, 3, 4, 5 and 0, where 0 means
never downshift.

Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---
 drivers/net/phy/microchip.c  | 33 +++++++++++++++++++++++++++++++++
 drivers/net/usb/lan78xx.c    |  8 ++++++--
 include/linux/microchipphy.h | 11 +++++++++++
 3 files changed, 50 insertions(+), 2 deletions(-)

--- a/drivers/net/phy/microchip.c
+++ b/drivers/net/phy/microchip.c
@@ -21,6 +21,7 @@
 #include <linux/phy.h>
 #include <linux/microchipphy.h>
 #include <linux/delay.h>
+#include <linux/of.h>
 
 #define DRIVER_AUTHOR	"WOOJUNG HUH <woojung.huh@microchip.com>"
 #define DRIVER_DESC	"Microchip LAN88XX PHY driver"
@@ -225,6 +226,7 @@ static int lan88xx_probe(struct phy_devi
 {
 	struct device *dev = &phydev->mdio.dev;
 	struct lan88xx_priv *priv;
+	u32 downshift_after = 0;
 
 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
@@ -232,6 +234,37 @@ static int lan88xx_probe(struct phy_devi
 
 	priv->wolopts = 0;
 
+	if (!of_property_read_u32(dev->of_node,
+				  "microchip,downshift-after",
+				  &downshift_after)) {
+		u32 mask = LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_MASK;
+		u32 val = LAN78XX_PHY_CTRL3_AUTO_DOWNSHIFT;
+
+		switch (downshift_after) {
+		case 2:
+			val |= LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_2;
+			break;
+		case 3:
+			val |= LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_3;
+			break;
+		case 4:
+			val |= LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_4;
+			break;
+		case 5:
+			val |= LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_5;
+			break;
+		case 0:
+			/* Disable completely */
+			mask = LAN78XX_PHY_CTRL3_AUTO_DOWNSHIFT;
+			val = 0;
+			break;
+		default:
+			return -EINVAL;
+		}
+		(void)phy_modify_paged(phydev, 1, LAN78XX_PHY_CTRL3,
+				       mask, val);
+	}
+
 	/* these values can be used to identify internal PHY */
 	priv->chip_id = phy_read_mmd(phydev, 3, LAN88XX_MMD3_CHIP_ID);
 	priv->chip_rev = phy_read_mmd(phydev, 3, LAN88XX_MMD3_CHIP_REV);
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -37,7 +37,8 @@
 #include <linux/irq.h>
 #include <linux/irqchip/chained_irq.h>
 #include <linux/microchipphy.h>
-#include <linux/phy.h>
+#include <linux/phy_fixed.h>
+#include <linux/of_mdio.h>
 #include <linux/of_net.h>
 #include "lan78xx.h"
 
@@ -1764,6 +1765,7 @@ done:
 
 static int lan78xx_mdio_init(struct lan78xx_net *dev)
 {
+	struct device_node *node;
 	int ret;
 
 	dev->mdiobus = mdiobus_alloc();
@@ -1793,7 +1795,9 @@ static int lan78xx_mdio_init(struct lan7
 		break;
 	}
 
-	ret = mdiobus_register(dev->mdiobus);
+	node = of_get_child_by_name(dev->udev->dev.of_node, "mdio");
+	ret = of_mdiobus_register(dev->mdiobus, node);
+	of_node_put(node);
 	if (ret) {
 		netdev_err(dev->net, "can't register MDIO bus\n");
 		goto exit1;
--- a/include/linux/microchipphy.h
+++ b/include/linux/microchipphy.h
@@ -70,6 +70,17 @@
 #define	LAN88XX_MMD3_CHIP_ID			(32877)
 #define	LAN88XX_MMD3_CHIP_REV			(32878)
 
+/* Registers specific to the LAN7800/LAN7850 embedded phy */
+#define LAN78XX_PHY_LED_MODE_SELECT		(0x1D)
+
+#define LAN78XX_PHY_CTRL3			(0x14)
+#define LAN78XX_PHY_CTRL3_AUTO_DOWNSHIFT	(0x0010)
+#define LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_MASK	(0x000c)
+#define LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_2	(0x0000)
+#define LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_3	(0x0004)
+#define LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_4	(0x0008)
+#define LAN78XX_PHY_CTRL3_DOWNSHIFT_CTRL_5	(0x000c)
+
 /* DSP registers */
 #define PHY_ARDENNES_MMD_DEV_3_PHY_CFG		(0x806A)
 #define PHY_ARDENNES_MMD_DEV_3_PHY_CFG_ZD_DLY_EN_	(0x2000)