mlxsw: Introduce support for I2C bus

Add I2C bus implementation for Mellanox Technologies Switch ASICs.
This includes command interface implementation using input / out mailboxes,
whose location is retrieved from the firmware during probe time.
Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/Kconfig

@@ -29,6 +29,16 @@ config MLXSW_PCI
 	  To compile this driver as a module, choose M here: the
 	  module will be called mlxsw_pci.
 
+config MLXSW_I2C
+	tristate "I2C bus implementation for Mellanox Technologies Switch ASICs"
+	depends on I2C && MLXSW_CORE
+	default m
+	---help---
+	  This is I2C bus implementation for Mellanox Technologies Switch ASICs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called mlxsw_i2c.
+
 config MLXSW_SWITCHIB
 	tristate "Mellanox Technologies SwitchIB and SwitchIB-2 support"
 	depends on MLXSW_CORE && NET_SWITCHDEV

drivers/net/ethernet/mellanox/mlxsw/Makefile

@@ -3,6 +3,8 @@ mlxsw_core-objs			:= core.o
 mlxsw_core-$(CONFIG_MLXSW_CORE_HWMON) += core_hwmon.o
 obj-$(CONFIG_MLXSW_PCI)		+= mlxsw_pci.o
 mlxsw_pci-objs			:= pci.o
+obj-$(CONFIG_MLXSW_I2C)		+= mlxsw_i2c.o
+mlxsw_i2c-objs			:= i2c.o
 obj-$(CONFIG_MLXSW_SWITCHIB)	+= mlxsw_switchib.o
 mlxsw_switchib-objs		:= switchib.o
 obj-$(CONFIG_MLXSW_SWITCHX2)	+= mlxsw_switchx2.o

drivers/net/ethernet/mellanox/mlxsw/i2c.c

+/*
+ * drivers/net/ethernet/mellanox/mlxsw/i2c.c
+ * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2016 Vadim Pasternak <vadimp@mellanox.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the names of the copyright holders nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/mutex.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/slab.h>
+
+#include "cmd.h"
+#include "core.h"
+#include "i2c.h"
+
+static const char mlxsw_i2c_driver_name[] = "mlxsw_i2c";
+
+#define MLXSW_I2C_CIR2_BASE		0x72000
+#define MLXSW_I2C_CIR_STATUS_OFF	0x18
+#define MLXSW_I2C_CIR2_OFF_STATUS	(MLXSW_I2C_CIR2_BASE + \
+					 MLXSW_I2C_CIR_STATUS_OFF)
+#define MLXSW_I2C_OPMOD_SHIFT		12
+#define MLXSW_I2C_GO_BIT_SHIFT		23
+#define MLXSW_I2C_CIR_CTRL_STATUS_SHIFT	24
+#define MLXSW_I2C_GO_BIT		BIT(MLXSW_I2C_GO_BIT_SHIFT)
+#define MLXSW_I2C_GO_OPMODE		BIT(MLXSW_I2C_OPMOD_SHIFT)
+#define MLXSW_I2C_SET_IMM_CMD		(MLXSW_I2C_GO_OPMODE | \
+					 MLXSW_CMD_OPCODE_QUERY_FW)
+#define MLXSW_I2C_PUSH_IMM_CMD		(MLXSW_I2C_GO_BIT | \
+					 MLXSW_I2C_SET_IMM_CMD)
+#define MLXSW_I2C_SET_CMD		(MLXSW_CMD_OPCODE_ACCESS_REG)
+#define MLXSW_I2C_PUSH_CMD		(MLXSW_I2C_GO_BIT | MLXSW_I2C_SET_CMD)
+#define MLXSW_I2C_TLV_HDR_SIZE		0x10
+#define MLXSW_I2C_ADDR_WIDTH		4
+#define MLXSW_I2C_PUSH_CMD_SIZE		(MLXSW_I2C_ADDR_WIDTH + 4)
+#define MLXSW_I2C_READ_SEMA_SIZE	4
+#define MLXSW_I2C_PREP_SIZE		(MLXSW_I2C_ADDR_WIDTH + 28)
+#define MLXSW_I2C_MBOX_SIZE		20
+#define MLXSW_I2C_MBOX_OUT_PARAM_OFF	12
+#define MLXSW_I2C_MAX_BUFF_SIZE		32
+#define MLXSW_I2C_MBOX_OFFSET_BITS	20
+#define MLXSW_I2C_MBOX_SIZE_BITS	12
+#define MLXSW_I2C_ADDR_BUF_SIZE		4
+#define MLXSW_I2C_BLK_MAX		32
+#define MLXSW_I2C_RETRY			5
+#define MLXSW_I2C_TIMEOUT_MSECS		5000
+
+/**
+ * struct mlxsw_i2c - device private data:
+ * @cmd.mb_size_in: input mailbox size;
+ * @cmd.mb_off_in: input mailbox offset in register space;
+ * @cmd.mb_size_out: output mailbox size;
+ * @cmd.mb_off_out: output mailbox offset in register space;
+ * @cmd.lock: command execution lock;
+ * @dev: I2C device;
+ * @core: switch core pointer;
+ * @bus_info: bus info block;
+ */
+struct mlxsw_i2c {
+	struct {
+		u32 mb_size_in;
+		u32 mb_off_in;
+		u32 mb_size_out;
+		u32 mb_off_out;
+		struct mutex lock;
+	} cmd;
+	struct device *dev;
+	struct mlxsw_core *core;
+	struct mlxsw_bus_info bus_info;
+};
+
+#define MLXSW_I2C_READ_MSG(_client, _addr_buf, _buf, _len) {	\
+	{ .addr = (_client)->addr,				\
+	  .buf = (_addr_buf),					\
+	  .len = MLXSW_I2C_ADDR_BUF_SIZE,			\
+	  .flags = 0 },						\
+	{ .addr = (_client)->addr,				\
+	  .buf = (_buf),					\
+	  .len = (_len),					\
+	  .flags = I2C_M_RD } }
+
+#define MLXSW_I2C_WRITE_MSG(_client, _buf, _len)		\
+	{ .addr = (_client)->addr,				\
+	  .buf = (u8 *)(_buf),					\
+	  .len = (_len),					\
+	  .flags = 0 }
+
+/* Routine converts in and out mail boxes offset and size. */
+static inline void
+mlxsw_i2c_convert_mbox(struct mlxsw_i2c *mlxsw_i2c, u8 *buf)
+{
+	u32 tmp;
+
+	/* Local in/out mailboxes: 20 bits for offset, 12 for size */
+	tmp = be32_to_cpup((__be32 *) buf);
+	mlxsw_i2c->cmd.mb_off_in = tmp &
+				   GENMASK(MLXSW_I2C_MBOX_OFFSET_BITS - 1, 0);
+	mlxsw_i2c->cmd.mb_size_in = (tmp & GENMASK(31,
+					MLXSW_I2C_MBOX_OFFSET_BITS)) >>
+					MLXSW_I2C_MBOX_OFFSET_BITS;
+
+	tmp = be32_to_cpup((__be32 *) (buf + MLXSW_I2C_ADDR_WIDTH));
+	mlxsw_i2c->cmd.mb_off_out = tmp &
+				    GENMASK(MLXSW_I2C_MBOX_OFFSET_BITS - 1, 0);
+	mlxsw_i2c->cmd.mb_size_out = (tmp & GENMASK(31,
+					MLXSW_I2C_MBOX_OFFSET_BITS)) >>
+					MLXSW_I2C_MBOX_OFFSET_BITS;
+}
+
+/* Routine obtains register size from mail box buffer. */
+static inline int mlxsw_i2c_get_reg_size(u8 *in_mbox)
+{
+	u16  tmp = be16_to_cpup((__be16 *) (in_mbox + MLXSW_I2C_TLV_HDR_SIZE));
+
+	return (tmp & 0x7ff) * 4 + MLXSW_I2C_TLV_HDR_SIZE;
+}
+
+/* Routine sets I2C device internal offset in the transaction buffer. */
+static inline void mlxsw_i2c_set_slave_addr(u8 *buf, u32 off)
+{
+	__be32 *val = (__be32 *) buf;
+
+	*val = htonl(off);
+}
+
+/* Routine waits until go bit is cleared. */
+static int mlxsw_i2c_wait_go_bit(struct i2c_client *client,
+				 struct mlxsw_i2c *mlxsw_i2c, u8 *p_status)
+{
+	u8 addr_buf[MLXSW_I2C_ADDR_BUF_SIZE];
+	u8 buf[MLXSW_I2C_READ_SEMA_SIZE];
+	int len = MLXSW_I2C_READ_SEMA_SIZE;
+	struct i2c_msg read_sema[] =
+		MLXSW_I2C_READ_MSG(client, addr_buf, buf, len);
+	bool wait_done = false;
+	unsigned long end;
+	int i = 0, err;
+
+	mlxsw_i2c_set_slave_addr(addr_buf, MLXSW_I2C_CIR2_OFF_STATUS);
+
+	end = jiffies + msecs_to_jiffies(MLXSW_I2C_TIMEOUT_MSECS);
+	do {
+		u32 ctrl;
+
+		err = i2c_transfer(client->adapter, read_sema,
+				   ARRAY_SIZE(read_sema));
+
+		ctrl = be32_to_cpu(*(__be32 *) buf);
+		if (err == ARRAY_SIZE(read_sema)) {
+			if (!(ctrl & MLXSW_I2C_GO_BIT)) {
+				wait_done = true;
+				*p_status = ctrl >>
+					    MLXSW_I2C_CIR_CTRL_STATUS_SHIFT;
+				break;
+			}
+		}
+		cond_resched();
+	} while ((time_before(jiffies, end)) || (i++ < MLXSW_I2C_RETRY));
+
+	if (wait_done) {
+		if (*p_status)
+			err = -EIO;
+	} else {
+		return -ETIMEDOUT;
+	}
+
+	return err > 0 ? 0 : err;
+}
+
+/* Routine posts a command to ASIC though mail box. */
+static int mlxsw_i2c_write_cmd(struct i2c_client *client,
+			       struct mlxsw_i2c *mlxsw_i2c,
+			       int immediate)
+{
+	__be32 push_cmd_buf[MLXSW_I2C_PUSH_CMD_SIZE / 4] = {
+		0, cpu_to_be32(MLXSW_I2C_PUSH_IMM_CMD)
+	};
+	__be32 prep_cmd_buf[MLXSW_I2C_PREP_SIZE / 4] = {
+		0, 0, 0, 0, 0, 0,
+		cpu_to_be32(client->adapter->nr & 0xffff),
+		cpu_to_be32(MLXSW_I2C_SET_IMM_CMD)
+	};
+	struct i2c_msg push_cmd =
+		MLXSW_I2C_WRITE_MSG(client, push_cmd_buf,
+				    MLXSW_I2C_PUSH_CMD_SIZE);
+	struct i2c_msg prep_cmd =
+		MLXSW_I2C_WRITE_MSG(client, prep_cmd_buf, MLXSW_I2C_PREP_SIZE);
+	int err;
+
+	if (!immediate) {
+		push_cmd_buf[1] = cpu_to_be32(MLXSW_I2C_PUSH_CMD);
+		prep_cmd_buf[7] = cpu_to_be32(MLXSW_I2C_SET_CMD);
+	}
+	mlxsw_i2c_set_slave_addr((u8 *)prep_cmd_buf,
+				 MLXSW_I2C_CIR2_BASE);
+	mlxsw_i2c_set_slave_addr((u8 *)push_cmd_buf,
+				 MLXSW_I2C_CIR2_OFF_STATUS);
+
+	/* Prepare Command Interface Register for transaction */
+	err = i2c_transfer(client->adapter, &prep_cmd, 1);
+	if (err < 0)
+		return err;
+	else if (err != 1)
+		return -EIO;
+
+	/* Write out Command Interface Register GO bit to push transaction */
+	err = i2c_transfer(client->adapter, &push_cmd, 1);
+	if (err < 0)
+		return err;
+	else if (err != 1)
+		return -EIO;
+
+	return 0;
+}
+
+/* Routine obtains mail box offsets from ASIC register space. */
+static int mlxsw_i2c_get_mbox(struct i2c_client *client,
+			      struct mlxsw_i2c *mlxsw_i2c)
+{
+	u8 addr_buf[MLXSW_I2C_ADDR_BUF_SIZE];
+	u8 buf[MLXSW_I2C_MBOX_SIZE];
+	struct i2c_msg mbox_cmd[] =
+		MLXSW_I2C_READ_MSG(client, addr_buf, buf, MLXSW_I2C_MBOX_SIZE);
+	int err;
+
+	/* Read mail boxes offsets. */
+	mlxsw_i2c_set_slave_addr(addr_buf, MLXSW_I2C_CIR2_BASE);
+	err = i2c_transfer(client->adapter, mbox_cmd, 2);
+	if (err != 2) {
+		dev_err(&client->dev, "Could not obtain mail boxes\n");
+		if (!err)
+			return -EIO;
+		else
+			return err;
+	}
+
+	/* Convert mail boxes. */
+	mlxsw_i2c_convert_mbox(mlxsw_i2c, &buf[MLXSW_I2C_MBOX_OUT_PARAM_OFF]);
+
+	return err;
+}
+
+/* Routine sends I2C write transaction to ASIC device. */
+static int
+mlxsw_i2c_write(struct device *dev, size_t in_mbox_size, u8 *in_mbox, int num,
+		u8 *p_status)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct mlxsw_i2c *mlxsw_i2c = i2c_get_clientdata(client);
+	unsigned long timeout = msecs_to_jiffies(MLXSW_I2C_TIMEOUT_MSECS);
+	u8 tran_buf[MLXSW_I2C_MAX_BUFF_SIZE + MLXSW_I2C_ADDR_BUF_SIZE];
+	int off = mlxsw_i2c->cmd.mb_off_in, chunk_size, i, j;
+	unsigned long end;
+	struct i2c_msg write_tran =
+		MLXSW_I2C_WRITE_MSG(client, tran_buf, MLXSW_I2C_PUSH_CMD_SIZE);
+	int err;
+
+	for (i = 0; i < num; i++) {
+		chunk_size = (in_mbox_size > MLXSW_I2C_BLK_MAX) ?
+			     MLXSW_I2C_BLK_MAX : in_mbox_size;
+		write_tran.len = MLXSW_I2C_ADDR_WIDTH + chunk_size;
+		mlxsw_i2c_set_slave_addr(tran_buf, off);
+		memcpy(&tran_buf[MLXSW_I2C_ADDR_BUF_SIZE], in_mbox +
+		       chunk_size * i, chunk_size);
+
+		j = 0;
+		end = jiffies + timeout;
+		do {
+			err = i2c_transfer(client->adapter, &write_tran, 1);
+			if (err == 1)
+				break;
+
+			cond_resched();
+		} while ((time_before(jiffies, end)) ||
+			 (j++ < MLXSW_I2C_RETRY));
+
+		if (err != 1) {
+			if (!err)
+				err = -EIO;
+			return err;
+		}
+
+		off += chunk_size;
+		in_mbox_size -= chunk_size;
+	}
+
+	/* Prepare and write out Command Interface Register for transaction. */
+	err = mlxsw_i2c_write_cmd(client, mlxsw_i2c, 0);
+	if (err) {
+		dev_err(&client->dev, "Could not start transaction");
+		return -EIO;
+	}
+
+	/* Wait until go bit is cleared. */
+	err = mlxsw_i2c_wait_go_bit(client, mlxsw_i2c, p_status);
+	if (err) {
+		dev_err(&client->dev, "HW semaphore is not released");
+		return err;
+	}
+
+	/* Validate transaction completion status. */
+	if (*p_status) {
+		dev_err(&client->dev, "Bad transaction completion status %x\n",
+			*p_status);
+		return -EIO;
+	}
+
+	return err > 0 ? 0 : err;
+}
+
+/* Routine executes I2C command. */
+static int
+mlxsw_i2c_cmd(struct device *dev, size_t in_mbox_size, u8 *in_mbox,
+	      size_t out_mbox_size, u8 *out_mbox, u8 *status)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct mlxsw_i2c *mlxsw_i2c = i2c_get_clientdata(client);
+	unsigned long timeout = msecs_to_jiffies(MLXSW_I2C_TIMEOUT_MSECS);
+	u8 tran_buf[MLXSW_I2C_ADDR_BUF_SIZE];
+	int num, chunk_size, reg_size, i, j;
+	int off = mlxsw_i2c->cmd.mb_off_out;
+	unsigned long end;
+	struct i2c_msg read_tran[] =
+		MLXSW_I2C_READ_MSG(client, tran_buf, NULL, 0);
+	int err;
+
+	WARN_ON(in_mbox_size % sizeof(u32) || out_mbox_size % sizeof(u32));
+
+	reg_size = mlxsw_i2c_get_reg_size(in_mbox);
+	num = reg_size / MLXSW_I2C_BLK_MAX;
+	if (reg_size % MLXSW_I2C_BLK_MAX)
+		num++;
+
+	if (mutex_lock_interruptible(&mlxsw_i2c->cmd.lock) < 0) {
+		dev_err(&client->dev, "Could not acquire lock");
+		return -EINVAL;
+	}
+
+	err = mlxsw_i2c_write(dev, reg_size, in_mbox, num, status);
+	if (err)
+		goto cmd_fail;
+
+	/* No out mailbox is case of write transaction. */
+	if (!out_mbox) {
+		mutex_unlock(&mlxsw_i2c->cmd.lock);
+		return 0;
+	}
+
+	/* Send read transaction to get output mailbox content. */
+	read_tran[1].buf = out_mbox;
+	for (i = 0; i < num; i++) {
+		chunk_size = (reg_size > MLXSW_I2C_BLK_MAX) ?
+			     MLXSW_I2C_BLK_MAX : reg_size;
+		read_tran[1].len = chunk_size;
+		mlxsw_i2c_set_slave_addr(tran_buf, off);
+
+		j = 0;
+		end = jiffies + timeout;
+		do {
+			err = i2c_transfer(client->adapter, read_tran,
+					   ARRAY_SIZE(read_tran));
+			if (err == ARRAY_SIZE(read_tran))
+				break;
+
+			cond_resched();
+		} while ((time_before(jiffies, end)) ||
+			 (j++ < MLXSW_I2C_RETRY));
+
+		if (err != ARRAY_SIZE(read_tran)) {
+			if (!err)
+				err = -EIO;
+
+			goto cmd_fail;
+		}
+
+		off += chunk_size;
+		reg_size -= chunk_size;
+		read_tran[1].buf += chunk_size;
+	}
+
+	mutex_unlock(&mlxsw_i2c->cmd.lock);
+
+	return 0;
+
+cmd_fail:
+	mutex_unlock(&mlxsw_i2c->cmd.lock);
+	return err;
+}
+
+static int mlxsw_i2c_cmd_exec(void *bus_priv, u16 opcode, u8 opcode_mod,
+			      u32 in_mod, bool out_mbox_direct,
+			      char *in_mbox, size_t in_mbox_size,
+			      char *out_mbox, size_t out_mbox_size,
+			      u8 *status)
+{
+	struct mlxsw_i2c *mlxsw_i2c = bus_priv;
+
+	return mlxsw_i2c_cmd(mlxsw_i2c->dev, in_mbox_size, in_mbox,
+			     out_mbox_size, out_mbox, status);
+}
+
+static bool mlxsw_i2c_skb_transmit_busy(void *bus_priv,
+					const struct mlxsw_tx_info *tx_info)
+{
+	return false;
+}
+
+static int mlxsw_i2c_skb_transmit(void *bus_priv, struct sk_buff *skb,
+				  const struct mlxsw_tx_info *tx_info)
+{
+	return 0;
+}
+
+static int
+mlxsw_i2c_init(void *bus_priv, struct mlxsw_core *mlxsw_core,
+	       const struct mlxsw_config_profile *profile,
+	       struct mlxsw_res *resources)
+{
+	struct mlxsw_i2c *mlxsw_i2c = bus_priv;
+
+	mlxsw_i2c->core = mlxsw_core;
+
+	return 0;
+}
+
+static void mlxsw_i2c_fini(void *bus_priv)
+{
+	struct mlxsw_i2c *mlxsw_i2c = bus_priv;
+
+	mlxsw_i2c->core = NULL;
+}
+
+static const struct mlxsw_bus mlxsw_i2c_bus = {
+	.kind			= "i2c",
+	.init			= mlxsw_i2c_init,
+	.fini			= mlxsw_i2c_fini,
+	.skb_transmit_busy	= mlxsw_i2c_skb_transmit_busy,
+	.skb_transmit		= mlxsw_i2c_skb_transmit,
+	.cmd_exec		= mlxsw_i2c_cmd_exec,
+};
+
+static int mlxsw_i2c_probe(struct i2c_client *client,
+			   const struct i2c_device_id *id)
+{
+	struct mlxsw_i2c *mlxsw_i2c;
+	u8 status;
+	int err;
+
+	mlxsw_i2c = devm_kzalloc(&client->dev, sizeof(*mlxsw_i2c), GFP_KERNEL);
+	if (!mlxsw_i2c)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, mlxsw_i2c);
+	mutex_init(&mlxsw_i2c->cmd.lock);
+
+	/* In order to use mailboxes through the i2c, special area is reserved
+	 * on the i2c address space that can be used for input and output
+	 * mailboxes. Such mailboxes are called local mailboxes. When using a
+	 * local mailbox, software should specify 0 as the Input/Output
+	 * parameters. The location of the Local Mailbox addresses on the i2c
+	 * space can be retrieved through the QUERY_FW command.
+	 * For this purpose QUERY_FW is to be issued with opcode modifier equal
+	 * 0x01. For such command the output parameter is an immediate value.
+	 * Here QUERY_FW command is invoked for ASIC probing and for getting
+	 * local mailboxes addresses from immedate output parameters.
+	 */
+
+	/* Prepare and write out Command Interface Register for transaction */
+	err = mlxsw_i2c_write_cmd(client, mlxsw_i2c, 1);
+	if (err) {
+		dev_err(&client->dev, "Could not start transaction");
+		goto errout;
+	}
+
+	/* Wait until go bit is cleared. */
+	err = mlxsw_i2c_wait_go_bit(client, mlxsw_i2c, &status);
+	if (err) {
+		dev_err(&client->dev, "HW semaphore is not released");
+		goto errout;
+	}
+
+	/* Validate transaction completion status. */
+	if (status) {
+		dev_err(&client->dev, "Bad transaction completion status %x\n",
+			status);
+		err = -EIO;
+		goto errout;
+	}
+
+	/* Get mailbox offsets. */
+	err = mlxsw_i2c_get_mbox(client, mlxsw_i2c);
+	if (err < 0) {
+		dev_err(&client->dev, "Fail to get mailboxes\n");
+		goto errout;
+	}
+
+	dev_info(&client->dev, "%s mb size=%x off=0x%08x out mb size=%x off=0x%08x\n",
+		 id->name, mlxsw_i2c->cmd.mb_size_in,
+		 mlxsw_i2c->cmd.mb_off_in, mlxsw_i2c->cmd.mb_size_out,
+		 mlxsw_i2c->cmd.mb_off_out);
+
+	/* Register device bus. */
+	mlxsw_i2c->bus_info.device_kind = id->name;
+	mlxsw_i2c->bus_info.device_name = client->name;
+	mlxsw_i2c->bus_info.dev = &client->dev;
+	mlxsw_i2c->dev = &client->dev;
+
+	err = mlxsw_core_bus_device_register(&mlxsw_i2c->bus_info,
+					     &mlxsw_i2c_bus, mlxsw_i2c);
+	if (err) {
+		dev_err(&client->dev, "Fail to register core bus\n");
+		return err;
+	}
+
+	return 0;
+
+errout:
+	i2c_set_clientdata(client, NULL);
+
+	return err;
+}
+
+static int mlxsw_i2c_remove(struct i2c_client *client)
+{
+	struct mlxsw_i2c *mlxsw_i2c = i2c_get_clientdata(client);
+
+	mlxsw_core_bus_device_unregister(mlxsw_i2c->core);
+	mutex_destroy(&mlxsw_i2c->cmd.lock);
+
+	return 0;
+}
+
+int mlxsw_i2c_driver_register(struct i2c_driver *i2c_driver)
+{
+	i2c_driver->probe = mlxsw_i2c_probe;
+	i2c_driver->remove = mlxsw_i2c_remove;
+	return i2c_add_driver(i2c_driver);
+}
+EXPORT_SYMBOL(mlxsw_i2c_driver_register);
+
+void mlxsw_i2c_driver_unregister(struct i2c_driver *i2c_driver)
+{
+	i2c_del_driver(i2c_driver);
+}
+EXPORT_SYMBOL(mlxsw_i2c_driver_unregister);
+
+MODULE_AUTHOR("Vadim Pasternak <vadimp@mellanox.com>");
+MODULE_DESCRIPTION("Mellanox switch I2C interface driver");
+MODULE_LICENSE("Dual BSD/GPL");

drivers/net/ethernet/mellanox/mlxsw/i2c.h

+/*
+ * drivers/net/ethernet/mellanox/mlxsw/i2c.h
+ * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2016 Vadim Pasternak <vadimp@mellanox.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the names of the copyright holders nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _MLXSW_I2C_H
+#define _MLXSW_I2C_H
+
+#include <linux/i2c.h>
+
+#if IS_ENABLED(CONFIG_MLXSW_I2C)
+
+int mlxsw_i2c_driver_register(struct i2c_driver *i2c_driver);
+void mlxsw_i2c_driver_unregister(struct i2c_driver *i2c_driver);
+
+#else
+
+static inline int
+mlxsw_i2c_driver_register(struct i2c_driver *i2c_driver)
+{
+	return -ENODEV;
+}
+
+static inline void
+mlxsw_i2c_driver_unregister(struct i2c_driver *i2c_driver)
+{
+}
+
+#endif
+
+#endif