net: dsa: mv88e6xxx: refine SMI support

The Marvell SOHO switches have several ways to access the internal
registers. One of them being the System Management Interface (SMI),
using the MDC and MDIO pins, with direct and indirect variants.

In preparation for adding support for other register accesses, move
the SMI code into its own files. At the same time, refine the code
to make it clear that the indirect variant is implemented using the
direct variant accessing only two registers for command and data.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 158 insertions, 0 deletions

diff --git a/drivers/net/dsa/mv88e6xxx/smi.c b/drivers/net/dsa/mv88e6xxx/smi.c
new file mode 100644
index 000000000000..96f7d2685bdc
--- /dev/null
+++ b/drivers/net/dsa/mv88e6xxx/smi.c
@@ -0,0 +1,158 @@
+/*
+ * Marvell 88E6xxx System Management Interface (SMI) support
+ *
+ * Copyright (c) 2008 Marvell Semiconductor
+ *
+ * Copyright (c) 2019 Vivien Didelot <vivien.didelot@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include "chip.h"
+#include "smi.h"
+
+/* The switch ADDR[4:1] configuration pins define the chip SMI device address
+ * (ADDR[0] is always zero, thus only even SMI addresses can be strapped).
+ *
+ * When ADDR is all zero, the chip uses Single-chip Addressing Mode, assuming it
+ * is the only device connected to the SMI master. In this mode it responds to
+ * all 32 possible SMI addresses, and thus maps directly the internal devices.
+ *
+ * When ADDR is non-zero, the chip uses Multi-chip Addressing Mode, allowing
+ * multiple devices to share the SMI interface. In this mode it responds to only
+ * 2 registers, used to indirectly access the internal SMI devices.
+ */
+
+static int mv88e6xxx_smi_direct_read(struct mv88e6xxx_chip *chip,
+				     int dev, int reg, u16 *data)
+{
+	int ret;
+
+	ret = mdiobus_read_nested(chip->bus, dev, reg);
+	if (ret < 0)
+		return ret;
+
+	*data = ret & 0xffff;
+
+	return 0;
+}
+
+static int mv88e6xxx_smi_direct_write(struct mv88e6xxx_chip *chip,
+				      int dev, int reg, u16 data)
+{
+	int ret;
+
+	ret = mdiobus_write_nested(chip->bus, dev, reg, data);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int mv88e6xxx_smi_direct_wait(struct mv88e6xxx_chip *chip,
+				     int dev, int reg, int bit, int val)
+{
+	u16 data;
+	int err;
+	int i;
+
+	for (i = 0; i < 16; i++) {
+		err = mv88e6xxx_smi_direct_read(chip, dev, reg, &data);
+		if (err)
+			return err;
+
+		if (!!(data >> bit) == !!val)
+			return 0;
+	}
+
+	return -ETIMEDOUT;
+}
+
+static const struct mv88e6xxx_bus_ops mv88e6xxx_smi_direct_ops = {
+	.read = mv88e6xxx_smi_direct_read,
+	.write = mv88e6xxx_smi_direct_write,
+};
+
+/* Offset 0x00: SMI Command Register
+ * Offset 0x01: SMI Data Register
+ */
+
+static int mv88e6xxx_smi_indirect_read(struct mv88e6xxx_chip *chip,
+				       int dev, int reg, u16 *data)
+{
+	int err;
+
+	err = mv88e6xxx_smi_direct_wait(chip, chip->sw_addr,
+					MV88E6XXX_SMI_CMD, 15, 0);
+	if (err)
+		return err;
+
+	err = mv88e6xxx_smi_direct_write(chip, chip->sw_addr,
+					 MV88E6XXX_SMI_CMD,
+					 MV88E6XXX_SMI_CMD_BUSY |
+					 MV88E6XXX_SMI_CMD_MODE_22 |
+					 MV88E6XXX_SMI_CMD_OP_22_READ |
+					 (dev << 5) | reg);
+	if (err)
+		return err;
+
+	err = mv88e6xxx_smi_direct_wait(chip, chip->sw_addr,
+					MV88E6XXX_SMI_CMD, 15, 0);
+	if (err)
+		return err;
+
+	return mv88e6xxx_smi_direct_read(chip, chip->sw_addr,
+					 MV88E6XXX_SMI_DATA, data);
+}
+
+static int mv88e6xxx_smi_indirect_write(struct mv88e6xxx_chip *chip,
+					int dev, int reg, u16 data)
+{
+	int err;
+
+	err = mv88e6xxx_smi_direct_wait(chip, chip->sw_addr,
+					MV88E6XXX_SMI_CMD, 15, 0);
+	if (err)
+		return err;
+
+	err = mv88e6xxx_smi_direct_write(chip, chip->sw_addr,
+					 MV88E6XXX_SMI_DATA, data);
+	if (err)
+		return err;
+
+	err = mv88e6xxx_smi_direct_write(chip, chip->sw_addr,
+					 MV88E6XXX_SMI_CMD,
+					 MV88E6XXX_SMI_CMD_BUSY |
+					 MV88E6XXX_SMI_CMD_MODE_22 |
+					 MV88E6XXX_SMI_CMD_OP_22_WRITE |
+					 (dev << 5) | reg);
+	if (err)
+		return err;
+
+	return mv88e6xxx_smi_direct_wait(chip, chip->sw_addr,
+					 MV88E6XXX_SMI_CMD, 15, 0);
+}
+
+static const struct mv88e6xxx_bus_ops mv88e6xxx_smi_indirect_ops = {
+	.read = mv88e6xxx_smi_indirect_read,
+	.write = mv88e6xxx_smi_indirect_write,
+};
+
+int mv88e6xxx_smi_init(struct mv88e6xxx_chip *chip,
+		       struct mii_bus *bus, int sw_addr)
+{
+	if (sw_addr == 0)
+		chip->smi_ops = &mv88e6xxx_smi_direct_ops;
+	else if (chip->info->multi_chip)
+		chip->smi_ops = &mv88e6xxx_smi_indirect_ops;
+	else
+		return -EINVAL;
+
+	chip->bus = bus;
+	chip->sw_addr = sw_addr;
+
+	return 0;
+}