Subject: [PATCH net-next 1/5] net: phy: mdio-i2c: support I2C MDIO protocol for RollBall SFP modules

From: Marek Behún <[email-masked]>
Date: Wed, 28 Oct 2020 23:14:23 +0100

Some multigig SFPs from RollBall and Hilink do not expose functional
MDIO access to the internal PHY of the SFP via I2C address 0x56
(although there seems to be read-only clause 22 access on this address).

Instead these SFPs PHY can be accessed via I2C via the SFP Enhanced
Digital Diagnostic Interface - I2C address 0x51.

This extends the mdio-i2c driver to support this protocol by adding a
special parameter to mdio_i2c_alloc function via which this RollBall
protocol can be selected.

Signed-off-by: Marek Behún <[email-masked]>
Cc: Andrew Lunn <[email-masked]>
Cc: Russell King <[email-masked]>
---
 drivers/net/mdio/mdio-i2c.c   | 180 +++++++++++++++++++++++++++++++++-
 drivers/net/phy/sfp.c         |   2 +-
 include/linux/mdio/mdio-i2c.h |   8 +-
 3 files changed, 183 insertions(+), 7 deletions(-)

diff --git a/drivers/net/mdio/mdio-i2c.c b/drivers/net/mdio/mdio-i2c.c
index 09200a70b315..1f5d653a4e22 100644
--- a/drivers/net/mdio/mdio-i2c.c
+++ b/drivers/net/mdio/mdio-i2c.c
@@ -3,6 +3,7 @@
  * MDIO I2C bridge
  *
  * Copyright (C) 2015-2016 Russell King
+ * Copyright (C) 2020 Marek Behun
  *
  * Network PHYs can appear on I2C buses when they are part of SFP module.
  * This driver exposes these PHYs to the networking PHY code, allowing
@@ -28,7 +29,7 @@ static unsigned int i2c_mii_phy_addr(int phy_id)
 	return phy_id + 0x40;
 }
 
-static int i2c_mii_read(struct mii_bus *bus, int phy_id, int reg)
+static int i2c_mii_read_default(struct mii_bus *bus, int phy_id, int reg)
 {
 	struct i2c_adapter *i2c = bus->priv;
 	struct i2c_msg msgs[2];
@@ -62,7 +63,7 @@ static int i2c_mii_read(struct mii_bus *bus, int phy_id, int reg)
 	return data[0] << 8 | data[1];
 }
 
-static int i2c_mii_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
+static int i2c_mii_write_default(struct mii_bus *bus, int phy_id, int reg, u16 val)
 {
 	struct i2c_adapter *i2c = bus->priv;
 	struct i2c_msg msg;
@@ -91,7 +92,167 @@ static int i2c_mii_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
 	return ret < 0 ? ret : 0;
 }
 
-struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c)
+/* RollBall SFPs do not access internal PHY via I2C address 0x56, but
+ * instead via address 0x51, when SFP page is set to 0x03 and password to
+ * 0xffffffff:
+ *
+ * address  size  contents  description
+ * -------  ----  --------  -----------
+ * 0x80     1     CMD       0x01/0x02/0x04 for write/read/done
+ * 0x81     1     DEV       Clause 45 device
+ * 0x82     2     REG       Clause 45 register
+ * 0x84     2     VAL       Register value
+ */
+#define ROLLBALL_PHY_I2C_ADDR		0x51
+
+#define ROLLBALL_CMD_ADDR		0x80
+#define ROLLBALL_DATA_ADDR		0x81
+
+#define ROLLBALL_CMD_WRITE		0x01
+#define ROLLBALL_CMD_READ		0x02
+#define ROLLBALL_CMD_DONE		0x04
+
+static int i2c_rollball_mii_poll(struct mii_bus *bus, int bus_addr, u8 *buf, size_t len)
+{
+	struct i2c_adapter *i2c = bus->priv;
+	struct i2c_msg msgs[2];
+	u8 buf0[2], *res;
+	int i, ret;
+
+	buf0[0] = ROLLBALL_CMD_ADDR;
+
+	msgs[0].addr = bus_addr;
+	msgs[0].flags = 0;
+	msgs[0].len = 1;
+	msgs[0].buf = &buf0[0];
+
+	res = buf ? buf : &buf0[1];
+
+	msgs[1].addr = bus_addr;
+	msgs[1].flags = I2C_M_RD;
+	msgs[1].len = buf ? len : 1;
+	msgs[1].buf = res;
+
+	/* By experiment it takes up to 70 ms to access a register for these SFPs. Sleep 20ms
+	 * between iteratios and try 10 times.
+	 */
+	i = 10;
+	do {
+		msleep(20);
+
+		ret = i2c_transfer(i2c, msgs, ARRAY_SIZE(msgs));
+		if (ret < 0)
+			return ret;
+		else if (ret != ARRAY_SIZE(msgs))
+			return -EIO;
+
+		if (*res == ROLLBALL_CMD_DONE)
+			return 0;
+	} while (i-- > 0);
+
+	dev_dbg(&bus->dev, "poll timed out\n");
+
+	return -ETIMEDOUT;
+}
+
+static int i2c_rollball_mii_cmd(struct mii_bus *bus, int bus_addr, u8 cmd, u8 *data, size_t len)
+{
+	struct i2c_adapter *i2c = bus->priv;
+	struct i2c_msg msgs[2];
+	u8 cmdbuf[2];
+	int ret;
+
+	msgs[0].addr = bus_addr;
+	msgs[0].flags = 0;
+	msgs[0].len = len;
+	msgs[0].buf = data;
+
+	cmdbuf[0] = ROLLBALL_CMD_ADDR;
+	cmdbuf[1] = cmd;
+
+	msgs[1].addr = bus_addr;
+	msgs[1].flags = 0;
+	msgs[1].len = sizeof(cmdbuf);
+	msgs[1].buf = cmdbuf;
+
+	ret = i2c_transfer(i2c, msgs, 2);
+	if (ret < 0)
+		return ret;
+
+	return ret == ARRAY_SIZE(msgs) ? 0 : -EIO;
+}
+
+static int i2c_mii_read_rollball(struct mii_bus *bus, int phy_id, int reg)
+{
+	u8 buf[4], res[6];
+	int bus_addr, ret;
+	u16 val;
+
+	if (!(reg & MII_ADDR_C45))
+		return -EOPNOTSUPP;
+
+	bus_addr = i2c_mii_phy_addr(phy_id);
+	if (bus_addr != ROLLBALL_PHY_I2C_ADDR)
+		return 0xffff;
+
+	buf[0] = ROLLBALL_DATA_ADDR;
+	buf[1] = (reg >> 16) & 0x1f;
+	buf[2] = (reg >> 8) & 0xff;
+	buf[3] = reg & 0xff;
+
+	ret = i2c_rollball_mii_cmd(bus, bus_addr, ROLLBALL_CMD_READ, buf, sizeof(buf));
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_rollball_mii_poll(bus, bus_addr, res, sizeof(res));
+	if (ret == -ETIMEDOUT)
+		return 0xffff;
+	else if (ret < 0)
+		return ret;
+
+	val = res[4];
+	val <<= 8;
+	val |= res[5];
+
+	dev_dbg(&bus->dev, "read reg %02x:%04x = %04x\n", (reg >> 16) & 0x1f, reg & 0xffff, val);
+
+	return val;
+}
+
+static int i2c_mii_write_rollball(struct mii_bus *bus, int phy_id, int reg, u16 val)
+{
+	int bus_addr, ret;
+	u8 buf[6];
+
+	if (!(reg & MII_ADDR_C45))
+		return -EOPNOTSUPP;
+
+	bus_addr = i2c_mii_phy_addr(phy_id);
+	if (bus_addr != ROLLBALL_PHY_I2C_ADDR)
+		return 0;
+
+	buf[0] = ROLLBALL_DATA_ADDR;
+	buf[1] = (reg >> 16) & 0x1f;
+	buf[2] = (reg >> 8) & 0xff;
+	buf[3] = reg & 0xff;
+	buf[4] = val >> 8;
+	buf[5] = val & 0xff;
+
+	ret = i2c_rollball_mii_cmd(bus, bus_addr, ROLLBALL_CMD_WRITE, buf, sizeof(buf));
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_rollball_mii_poll(bus, bus_addr, NULL, 0);
+	if (ret < 0)
+		return ret;
+
+	dev_dbg(&bus->dev, "write reg %02x:%04x = %04x\n", (reg >> 16) & 0x1f, reg & 0xffff, val);
+
+	return 0;
+}
+
+struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c,
+			       enum mdio_i2c_type type)
 {
 	struct mii_bus *mii;
 
@@ -104,10 +265,19 @@ struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c)
 
 	snprintf(mii->id, MII_BUS_ID_SIZE, "i2c:%s", dev_name(parent));
 	mii->parent = parent;
-	mii->read = i2c_mii_read;
-	mii->write = i2c_mii_write;
 	mii->priv = i2c;
 
+	switch (type) {
+	case MDIO_I2C_ROLLBALL:
+		mii->read = i2c_mii_read_rollball;
+		mii->write = i2c_mii_write_rollball;
+		break;
+	default:
+		mii->read = i2c_mii_read_default;
+		mii->write = i2c_mii_write_default;
+		break;
+	}
+
 	return mii;
 }
 EXPORT_SYMBOL_GPL(mdio_i2c_alloc);
diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index 1d18c10e8f82..b1f9fc3a5584 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -409,7 +409,7 @@ static int sfp_i2c_configure(struct sfp *sfp, struct i2c_adapter *i2c)
 	sfp->read = sfp_i2c_read;
 	sfp->write = sfp_i2c_write;
 
-	i2c_mii = mdio_i2c_alloc(sfp->dev, i2c);
+	i2c_mii = mdio_i2c_alloc(sfp->dev, i2c, MDIO_I2C_DEFAULT);
 	if (IS_ERR(i2c_mii))
 		return PTR_ERR(i2c_mii);
 
diff --git a/include/linux/mdio/mdio-i2c.h b/include/linux/mdio/mdio-i2c.h
index b1d27f7cd23f..b65a80938806 100644
--- a/include/linux/mdio/mdio-i2c.h
+++ b/include/linux/mdio/mdio-i2c.h
@@ -11,6 +11,12 @@ struct device;
 struct i2c_adapter;
 struct mii_bus;
 
-struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c);
+enum mdio_i2c_type {
+	MDIO_I2C_DEFAULT,
+	MDIO_I2C_ROLLBALL,
+};
+
+struct mii_bus *mdio_i2c_alloc(struct device *parent, struct i2c_adapter *i2c,
+			       enum mdio_i2c_type type);
 
 #endif
-- 
2.26.2