From 3cb0bde365d913c484d20224367a54a0eac780a7 Mon Sep 17 00:00:00 2001
From: Antoine Tenart <antoine.tenart@bootlin.com>
Date: Fri, 21 Feb 2020 11:55:29 +0100
Subject: [PATCH 3/3] net: phy: sfp: add support for SMBus

Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
---
 drivers/net/phy/sfp.c | 92 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 88 insertions(+), 4 deletions(-)

--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -662,10 +662,64 @@ static int sfp_i2c_write(struct sfp *sfp
 	return ret == ARRAY_SIZE(msgs) ? len : 0;
 }
 
+static int sfp_smbus_read(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
+			  size_t len)
+{
+	u8 bus_addr = a2 ? 0x51 : 0x50, *val = buf;
+	union i2c_smbus_data data;
+	int ret;
+
+	bus_addr -= 0x40;
+
+	while (len > 0) {
+		ret = i2c_smbus_xfer(sfp->i2c, i2c_mii_phy_addr(bus_addr), 0,
+				     I2C_SMBUS_READ, dev_addr,
+				     I2C_SMBUS_BYTE_DATA, &data);
+		if (ret)
+			return ret;
+		*val++ = data.byte;
+		dev_addr++;
+		len--;
+	}
+
+	return val - (u8 *)buf;
+}
+
+static int sfp_smbus_write(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
+			  size_t len)
+{
+	u8 bus_addr = a2 ? 0x51 : 0x50, *val = buf;
+	union i2c_smbus_data data;
+	int ret;
+
+	bus_addr -= 0x40;
+
+	while (len > 0) {
+		data.byte = *val++;
+		ret = i2c_smbus_xfer(sfp->i2c, i2c_mii_phy_addr(bus_addr), 0,
+				     I2C_SMBUS_WRITE, dev_addr,
+				     I2C_SMBUS_BYTE_DATA, &data);
+		if (ret)
+			return ret;
+		dev_addr++;
+		len--;
+	}
+
+	return val - (u8 *)buf;
+}
+
 static int sfp_i2c_configure(struct sfp *sfp, struct i2c_adapter *i2c)
 {
-	if (!i2c_check_functionality(i2c, I2C_FUNC_I2C))
-		return -EINVAL;
+	if (!i2c_check_functionality(i2c, I2C_FUNC_I2C)) {
+		if (i2c_check_functionality(i2c, I2C_FUNC_SMBUS_BYTE_DATA)) {
+			sfp->i2c = i2c;
+			sfp->read = sfp_smbus_read;
+			sfp->write = sfp_smbus_write;
+
+			return 0;
+		} else
+			return -EINVAL;
+	}
 
 	sfp->i2c = i2c;
 	sfp->read = sfp_i2c_read;
@@ -697,6 +751,29 @@ static int sfp_i2c_mdiobus_create(struct
 	return 0;
 }
 
+static int sfp_sm_mdiobus_create(struct sfp *sfp)
+{
+	struct mii_bus *sm_mii;
+	int ret;
+
+	sm_mii = mdio_smbus_alloc(sfp->dev, sfp->i2c);
+	if (IS_ERR(sm_mii))
+		return PTR_ERR(sm_mii);
+
+	sm_mii->name = "SFP SMBus";
+	sm_mii->phy_mask = ~0;
+
+	ret = mdiobus_register(sm_mii);
+	if (ret < 0) {
+		mdiobus_free(sm_mii);
+		return ret;
+	}
+
+	sfp->i2c_mii = sm_mii;
+
+	return 0;
+}
+
 static void sfp_i2c_mdiobus_destroy(struct sfp *sfp)
 {
 	mdiobus_unregister(sfp->i2c_mii);
@@ -1870,8 +1947,15 @@ static void sfp_sm_fault(struct sfp *sfp
 
 static int sfp_sm_add_mdio_bus(struct sfp *sfp)
 {
-	if (sfp->mdio_protocol != MDIO_I2C_NONE)
-		return sfp_i2c_mdiobus_create(sfp);
+	if (i2c_check_functionality(sfp->i2c, I2C_FUNC_I2C)) {
+		if (sfp->mdio_protocol != MDIO_I2C_NONE)
+			return sfp_i2c_mdiobus_create(sfp);
+
+		return 0;
+	}
+
+	if (i2c_check_functionality(sfp->i2c, I2C_FUNC_SMBUS_BYTE_DATA))
+		return sfp_sm_mdiobus_create(sfp);
 
 	return 0;
 }
