Message-Id: <1479660974-143713-1-git-send-email-vadimp@mellanox.com>
Date:   Sun, 20 Nov 2016 16:56:14 +0000
From:   vadimp@...lanox.com
To:     wsa@...-dreams.de
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        jiri@...nulli.us, Vadim Pasternak <vadimp@...lanox.com>,
        Michael Shych <michaelsh@...lanox.com>
Subject: [patch v9 1/1] i2c: add master driver for mellanox systems

From: Vadim Pasternak <vadimp@...lanox.com>

Device driver for Mellanox I2C controller logic, implemented in Lattice
CPLD device.
Device supports:
 - Master mode
 - One physical bus
 - Polling mode

The Kconfig currently controlling compilation of this code is:
drivers/i2c/busses/Kconfig:config I2C_MLXCPLD

Signed-off-by: Michael Shych <michaelsh@...lanox.com>
Signed-off-by: Vadim Pasternak <vadimp@...lanox.com>
Reviewed-by: Jiri Pirko <jiri@...lanox.com>
Reviewed-by: Vladimir Zapolskiy <vz@...ia.com>
---
v8->v9
 Comments pointed out by Wolfram:
  - fix typo in comment;
  - use quirk parameters for the message number validation;
v7->v8
 Comments pointed out by Wolfram:
 - Remove descriptions for two structures, since the members have
   self-explaining names;
 - Populate the structure i2c_adapter_quirks, so core will make length
   validation, as a result remove mlxcpld_i2c_invalid_len,
   and move common length calculation to mlxcpld_i2c_xfer. Consider
   removing of mlxcpld_i2c_check_msg_params after core quirks is able
   to handle messages full validation;
 - Use ENXIO error code for NACK;
v6->v7
 Comments pointed out by Peter:
 - Fix grammar in doc file;
 - Fix description for CMD in doc file;
 - Fix grammar for NUM_DATA, DATAx in doc file;
 - Rename mlxcpld_i2c_curr_transf to mlxcpld_i2c_curr_xfer;
 - Make code in mlxcpld_i2c_lpc_write_buf more readable and
   mlxcpld_i2c_lpc_read_buf, compact and elegant;
 - Fix multiline comments;
v5->v6:
 Comments pointed out by Vladimir:
 - Drop the line with module path from the header;
 - In description of mlxcpld_i2c_priv remove lpc_gen_dec_reg asnd dev_id;
 - In mlxcpld_i2c_priv change type of the filed base_addr to u16 for
   the alignment with in/out and remove unused dev_id;
 - Fix misspelling in comment for mlxcpld_i2c_invalid_len;
 - Remove comment regarding EBUSY return in mlxcpld_i2c_check_busy;
 - Use sizeof of the target storage in allocation in probe routine;
v4->v5:
 Comments pointed out by Vladimir:
 - Remove "default n" from Kconfig;
 - Fix the comments for timeout and pool time;
 - Optimize error flow in mlxcpld_i2c_probe;
v3->v4:
 Comments pointed out by Vladimir:
 - Set default to no in Kconfig;
 - Make mlxcpld_i2c_plat_dev static and add empty line before the
   declaration;
 - In function mlxcpld_i2c_invalid_len remove (msg->len < 0), since len is
   unsigned;
 - Remove unused symbol mlxcpld_i2c_plat_dev;
 - Remove extra spaces in comments to mlxcpld_i2c_check_msg_params;
 - Remove unnecessary round braces in mlxcpld_i2c_set_transf_data;
 - Remove the assignment of 'i' variable in mlxcpld_i2c_wait_for_tc;
 - Add extra line in mlxcpld_i2c_xfer;
 - Move assignment of the adapter's fields retries and nr inside
   mlxcpld_i2c_adapter declaration;
v2->v3:
 Comments pointed out by Vladimir:
 - Use tab symbol as indentation in Kconfig
 - Add the Kconfig section preserving the alphabetical order - added
   within "Other I2C/SMBus bus drivers" after I2C_ELEKTOR (but after this
   sections others are not follow alphabetical);
 - Change license to dual;
 - Replace ADRR with ADDR in macros;
 - Remove unused macros: MLXCPLD_LPCI2C_LPF_DFLT,
   MLXCPLD_LPCI2C_HALF_CYC_100, MLXCPLD_LPCI2C_I2C_HOLD_100,
   MLXCPLD_LPCI2C_HALF_CYC_REG, MLXCPLD_LPCI2C_I2C_HOLD_REG;
 - Fix checkpatch warnings (**/ and the end of comment);
 - Add empty line before structures mlxcpld_i2c_regs,
   mlxcpld_i2c_curr_transf, mlxcpld_i2c_priv;
 - Remove unused structure mlxcpld_i2c_regs;
 - Remove from mlxcpld_i2c_priv the next fields:
   retr_num, poll_time, block_sz, xfer_to; use instead macros
   respectively: MLXCPLD_I2C_RETR_NUM, MLXCPLD_I2C_POLL_TIME,
   MLXCPLD_I2C_DATA_REG_SZ, MLXCPLD_I2C_XFER_TO;
 - In mlxcpld_i2c_invalid_len remove unnecessary else;
 - Optimize mlxcpld_i2c_set_transf_data;
 - mlxcpld_i2c_reset - add empty lines after/before mutex
   lock/unlock;
 - mlxcpld_i2c_wait_for_free - cover case timeout is equal
   MLXCPLD_I2C_XFER_TO;
 - mlxcpld_i2c_wait_for_tc:
   - Do not assign err in declaration (also err is removed);
   - Insert empty line before case MLXCPLD_LPCI2C_ACK_IND;
   - inside case MLXCPLD_LPCI2C_ACK_IND - avoid unnecessary
     indentation;
   - Remove case MLXCPLD_LPCI2C_ERR_IND and remove this macro;
 - Add empty lines in mlxcpld_i2c_xfer before/after mutex_lock/
   mutex_unlock;
 - In mlxcpld_i2c_probe add emtpy line after platform_set_drvdata;
 - Replace platfrom handle pdev in mlxcpld_i2c_priv with the pointer
   to the structure device;
 - Place assignment of base_addr near the others;
 - Enclose e-mail with <>;
 Fixes added by Vadim:
 - Change structure description format according to
   Documentation/kernel-documentation.rst guideline;
 - mlxcpld_i2c_wait_for_tc: return error if status reaches default case;
v1->v2
 Fixes added by Vadim:
 - Put new record in Makefile in alphabetic order;
 - Remove http://www.mellanox.com from MAINTAINERS record;
---
 Documentation/i2c/busses/i2c-mlxcpld |  47 ++++
 MAINTAINERS                          |   8 +
 drivers/i2c/busses/Kconfig           |  11 +
 drivers/i2c/busses/Makefile          |   1 +
 drivers/i2c/busses/i2c-mlxcpld.c     | 504 +++++++++++++++++++++++++++++++++++
 5 files changed, 571 insertions(+)
 create mode 100644 Documentation/i2c/busses/i2c-mlxcpld
 create mode 100644 drivers/i2c/busses/i2c-mlxcpld.c

diff --git a/Documentation/i2c/busses/i2c-mlxcpld b/Documentation/i2c/busses/i2c-mlxcpld
new file mode 100644
index 0000000..4e46c44
--- /dev/null
+++ b/Documentation/i2c/busses/i2c-mlxcpld
@@ -0,0 +1,47 @@
+Driver i2c-mlxcpld
+
+Author: Michael Shych <michaelsh@...lanox.com>
+
+This is the Mellanox I2C controller logic, implemented in Lattice CPLD
+device.
+Device supports:
+ - Master mode.
+ - One physical bus.
+ - Polling mode.
+
+This controller is equipped within the next Mellanox systems:
+"msx6710", "msx6720", "msb7700", "msn2700", "msx1410", "msn2410", "msb7800",
+"msn2740", "msn2100".
+
+The next transaction types are supported:
+ - Receive Byte/Block.
+ - Send Byte/Block.
+ - Read Byte/Block.
+ - Write Byte/Block.
+
+Registers:
+CTRL		0x1 - control reg.
+			Resets all the registers.
+HALF_CYC	0x4 - cycle reg.
+			Configure the width of I2C SCL half clock cycle (in 4 LPC_CLK
+			units).
+I2C_HOLD	0x5 - hold reg.
+			OE (output enable) is delayed by value set to this register
+			(in LPC_CLK units)
+CMD			0x6 - command reg.
+			Bit 0, 0 = write, 1 = read.
+			Bits [7:1] - the 7bit Address of the I2C device.
+			It should be written last as it triggers an I2C transaction.
+NUM_DATA	0x7 - data size reg.
+			Number of data bytes to write in read transaction
+NUM_ADDR	0x8 - address reg.
+			Number of address bytes to write in read transaction.
+STATUS		0x9 - status reg.
+			Bit 0 - transaction is completed.
+			Bit 4 - ACK/NACK.
+DATAx		0xa - 0x54  - 68 bytes data buffer regs.
+			For write transaction address is specified in four first bytes
+			(DATA1 - DATA4), data starting from DATA4.
+			For read transactions address is sent in a separate transaction and
+			specified in the four first bytes (DATA0 - DATA3). Data is read
+			starting from DATA0.
diff --git a/MAINTAINERS b/MAINTAINERS
index 411e3b8..26d05f8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7881,6 +7881,14 @@ W:	http://www.mellanox.com
 Q:	http://patchwork.ozlabs.org/project/netdev/list/
 F:	drivers/net/ethernet/mellanox/mlxsw/
 
+MELLANOX MLXCPLD I2C DRIVER
+M:	Vadim Pasternak <vadimp@...lanox.com>
+M:	Michael Shych <michaelsh@...lanox.com>
+L:	linux-i2c@...r.kernel.org
+S:	Supported
+F:	drivers/i2c/busses/i2c-mlxcpld.c
+F:	Documentation/i2c/busses/i2c-mlxcpld
+
 MELLANOX MLXCPLD LED DRIVER
 M:	Vadim Pasternak <vadimp@...lanox.com>
 L:	linux-leds@...r.kernel.org
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index d252276..6399cea 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -1150,6 +1150,17 @@ config I2C_ELEKTOR
 	  This support is also available as a module.  If so, the module
 	  will be called i2c-elektor.
 
+config I2C_MLXCPLD
+	tristate "Mellanox I2C driver"
+	depends on X86_64
+	help
+	  This exposes the Mellanox platform I2C busses to the linux I2C layer
+	  for X86 based systems.
+	  Controller is implemented as CPLD logic.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called as i2c-mlxcpld.
+
 config I2C_PCA_ISA
 	tristate "PCA9564/PCA9665 on an ISA bus"
 	depends on ISA
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 29764cc..645bf08 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -116,6 +116,7 @@ obj-$(CONFIG_I2C_BCM_KONA)	+= i2c-bcm-kona.o
 obj-$(CONFIG_I2C_BRCMSTB)	+= i2c-brcmstb.o
 obj-$(CONFIG_I2C_CROS_EC_TUNNEL)	+= i2c-cros-ec-tunnel.o
 obj-$(CONFIG_I2C_ELEKTOR)	+= i2c-elektor.o
+obj-$(CONFIG_I2C_MLXCPLD)	+= i2c-mlxcpld.o
 obj-$(CONFIG_I2C_OPAL)		+= i2c-opal.o
 obj-$(CONFIG_I2C_PCA_ISA)	+= i2c-pca-isa.o
 obj-$(CONFIG_I2C_SIBYTE)	+= i2c-sibyte.o
diff --git a/drivers/i2c/busses/i2c-mlxcpld.c b/drivers/i2c/busses/i2c-mlxcpld.c
new file mode 100644
index 0000000..d271e6a
--- /dev/null
+++ b/drivers/i2c/busses/i2c-mlxcpld.c
@@ -0,0 +1,504 @@
+/*
+ * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2016 Michael Shych <michaels@...lanox.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/delay.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+/* General defines */
+#define MLXPLAT_CPLD_LPC_I2C_BASE_ADDR	0x2000
+#define MLXCPLD_I2C_DEVICE_NAME		"i2c_mlxcpld"
+#define MLXCPLD_I2C_VALID_FLAG		(I2C_M_RECV_LEN | I2C_M_RD)
+#define MLXCPLD_I2C_BUS_NUM		1
+#define MLXCPLD_I2C_DATA_REG_SZ		36
+#define MLXCPLD_I2C_MAX_ADDR_LEN	4
+#define MLXCPLD_I2C_RETR_NUM		2
+#define MLXCPLD_I2C_XFER_TO		500000 /* usec */
+#define MLXCPLD_I2C_POLL_TIME		2000   /* usec */
+
+/* LPC I2C registers */
+#define MLXCPLD_LPCI2C_LPF_REG		0x0
+#define MLXCPLD_LPCI2C_CTRL_REG		0x1
+#define MLXCPLD_LPCI2C_HALF_CYC_REG	0x4
+#define MLXCPLD_LPCI2C_I2C_HOLD_REG	0x5
+#define MLXCPLD_LPCI2C_CMD_REG		0x6
+#define MLXCPLD_LPCI2C_NUM_DAT_REG	0x7
+#define MLXCPLD_LPCI2C_NUM_ADDR_REG	0x8
+#define MLXCPLD_LPCI2C_STATUS_REG	0x9
+#define MLXCPLD_LPCI2C_DATA_REG		0xa
+
+/* LPC I2C masks and parametres */
+#define MLXCPLD_LPCI2C_RST_SEL_MASK	0x1
+#define MLXCPLD_LPCI2C_TRANS_END	0x1
+#define MLXCPLD_LPCI2C_STATUS_NACK	0x10
+#define MLXCPLD_LPCI2C_NO_IND		0
+#define MLXCPLD_LPCI2C_ACK_IND		1
+#define MLXCPLD_LPCI2C_NACK_IND		2
+
+struct  mlxcpld_i2c_curr_xfer {
+	u8 cmd;
+	u8 addr_width;
+	u8 data_len;
+	u8 msg_num;
+	struct i2c_msg *msg;
+};
+
+struct mlxcpld_i2c_priv {
+	struct i2c_adapter adap;
+	u32 base_addr;
+	struct mutex lock;
+	struct  mlxcpld_i2c_curr_xfer xfer;
+	struct device *dev;
+};
+
+static void mlxcpld_i2c_lpc_write_buf(u8 *data, u8 len, u32 addr)
+{
+	int i;
+
+	for (i = 0; i < len - len % 4; i += 4)
+		outl(*(u32 *)(data + i), addr + i);
+	for (; i < len; ++i)
+		outb(*(data + i), addr + i);
+}
+
+static void mlxcpld_i2c_lpc_read_buf(u8 *data, u8 len, u32 addr)
+{
+	int i;
+
+	for (i = 0; i < len - len % 4; i += 4)
+		*(u32 *)(data + i) = inl(addr + i);
+	for (; i < len; ++i)
+		*(data + i) = inb(addr + i);
+}
+
+static void mlxcpld_i2c_read_comm(struct mlxcpld_i2c_priv *priv, u8 offs,
+				  u8 *data, u8 datalen)
+{
+	u32 addr = priv->base_addr + offs;
+
+	switch (datalen) {
+	case 1:
+		*(data) = inb(addr);
+		break;
+	case 2:
+		*((u16 *)data) = inw(addr);
+		break;
+	case 3:
+		*((u16 *)data) = inw(addr);
+		*(data + 2) = inb(addr + 2);
+		break;
+	case 4:
+		*((u32 *)data) = inl(addr);
+		break;
+	default:
+		mlxcpld_i2c_lpc_read_buf(data, datalen, addr);
+		break;
+	}
+}
+
+static void mlxcpld_i2c_write_comm(struct mlxcpld_i2c_priv *priv, u8 offs,
+				   u8 *data, u8 datalen)
+{
+	u32 addr = priv->base_addr + offs;
+
+	switch (datalen) {
+	case 1:
+		outb(*(data), addr);
+		break;
+	case 2:
+		outw(*((u16 *)data), addr);
+		break;
+	case 3:
+		outw(*((u16 *)data), addr);
+		outb(*(data + 2), addr + 2);
+		break;
+	case 4:
+		outl(*((u32 *)data), addr);
+		break;
+	default:
+		mlxcpld_i2c_lpc_write_buf(data, datalen, addr);
+		break;
+	}
+}
+
+/*
+ * Check validity of received i2c messages parameters.
+ * Returns 0 if OK, other - in case of invalid parameters.
+ */
+static int mlxcpld_i2c_check_msg_params(struct mlxcpld_i2c_priv *priv,
+					struct i2c_msg *msgs, int num)
+{
+	int i;
+
+	if (!num) {
+		dev_err(priv->dev, "Incorrect 0 num of messages\n");
+		return -EINVAL;
+	}
+
+	if (unlikely(msgs[0].addr > 0x7f)) {
+		dev_err(priv->dev, "Invalid address 0x%03x\n",
+			msgs[0].addr);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < num; ++i) {
+		if (unlikely(!msgs[i].buf)) {
+			dev_err(priv->dev, "Invalid buf in msg[%d]\n",
+				i);
+			return -EINVAL;
+		}
+		if (unlikely(msgs[0].addr != msgs[i].addr)) {
+			dev_err(priv->dev, "Invalid addr in msg[%d]\n",
+				i);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Check if transfer is completed and status of operation.
+ * Returns 0 - transfer completed (both ACK or NACK),
+ * negative - transfer isn't finished.
+ */
+static int mlxcpld_i2c_check_status(struct mlxcpld_i2c_priv *priv, int *status)
+{
+	u8 val;
+
+	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_STATUS_REG, &val, 1);
+
+	if (val & MLXCPLD_LPCI2C_TRANS_END) {
+		if (val & MLXCPLD_LPCI2C_STATUS_NACK)
+			/*
+			 * The slave is unable to accept the data. No such
+			 * slave, command not understood, or unable to accept
+			 * any more data.
+			 */
+			*status = MLXCPLD_LPCI2C_NACK_IND;
+		else
+			*status = MLXCPLD_LPCI2C_ACK_IND;
+		return 0;
+	}
+	*status = MLXCPLD_LPCI2C_NO_IND;
+
+	return -EIO;
+}
+
+static void mlxcpld_i2c_set_transf_data(struct mlxcpld_i2c_priv *priv,
+					struct i2c_msg *msgs, int num,
+					u8 comm_len)
+{
+	priv->xfer.msg = msgs;
+	priv->xfer.msg_num = num;
+
+	/*
+	 * All upper layers currently are never use transfer with more than
+	 * 2 messages. Actually, it's also not so relevant in Mellanox systems
+	 * because of HW limitation. Max size of transfer is not more than 32
+	 * bytes in the current x86 LPCI2C bridge.
+	 */
+	priv->xfer.cmd = msgs[num - 1].flags & I2C_M_RD;
+
+	if (priv->xfer.cmd == I2C_M_RD && comm_len != msgs[0].len) {
+		priv->xfer.addr_width = msgs[0].len;
+		priv->xfer.data_len = comm_len - priv->xfer.addr_width;
+	} else {
+		priv->xfer.addr_width = 0;
+		priv->xfer.data_len = comm_len;
+	}
+}
+
+/* Reset CPLD LPCI2C block */
+static void mlxcpld_i2c_reset(struct mlxcpld_i2c_priv *priv)
+{
+	u8 val;
+
+	mutex_lock(&priv->lock);
+
+	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_CTRL_REG, &val, 1);
+	val &= ~MLXCPLD_LPCI2C_RST_SEL_MASK;
+	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_CTRL_REG, &val, 1);
+
+	mutex_unlock(&priv->lock);
+}
+
+/* Make sure the CPLD is ready to start transmitting. */
+static int mlxcpld_i2c_check_busy(struct mlxcpld_i2c_priv *priv)
+{
+	u8 val;
+
+	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_STATUS_REG, &val, 1);
+
+	if (val & MLXCPLD_LPCI2C_TRANS_END)
+		return 0;
+
+	return -EIO;
+}
+
+static int mlxcpld_i2c_wait_for_free(struct mlxcpld_i2c_priv *priv)
+{
+	int timeout = 0;
+
+	do {
+		if (!mlxcpld_i2c_check_busy(priv))
+			break;
+		usleep_range(MLXCPLD_I2C_POLL_TIME / 2, MLXCPLD_I2C_POLL_TIME);
+		timeout += MLXCPLD_I2C_POLL_TIME;
+	} while (timeout <= MLXCPLD_I2C_XFER_TO);
+
+	if (timeout > MLXCPLD_I2C_XFER_TO)
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+/*
+ * Wait for master transfer to complete.
+ * It puts current process to sleep until we get interrupt or timeout expires.
+ * Returns the number of transferred or read bytes or error (<0).
+ */
+static int mlxcpld_i2c_wait_for_tc(struct mlxcpld_i2c_priv *priv)
+{
+	int status, i, timeout = 0;
+	u8 datalen;
+
+	do {
+		usleep_range(MLXCPLD_I2C_POLL_TIME / 2, MLXCPLD_I2C_POLL_TIME);
+		if (!mlxcpld_i2c_check_status(priv, &status))
+			break;
+		timeout += MLXCPLD_I2C_POLL_TIME;
+	} while (status == 0 && timeout < MLXCPLD_I2C_XFER_TO);
+
+	switch (status) {
+	case MLXCPLD_LPCI2C_NO_IND:
+		return -ETIMEDOUT;
+
+	case MLXCPLD_LPCI2C_ACK_IND:
+		if (priv->xfer.cmd != I2C_M_RD)
+			return (priv->xfer.addr_width + priv->xfer.data_len);
+
+		if (priv->xfer.msg_num == 1)
+			i = 0;
+		else
+			i = 1;
+
+		if (!priv->xfer.msg[i].buf)
+			return -EINVAL;
+
+		/*
+		 * Actual read data len will be always the same as
+		 * requested len. 0xff (line pull-up) will be returned
+		 * if slave has no data to return. Thus don't read
+		 * MLXCPLD_LPCI2C_NUM_DAT_REG reg from CPLD.
+		 */
+		datalen = priv->xfer.data_len;
+
+		mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_DATA_REG,
+				      priv->xfer.msg[i].buf, datalen);
+
+		return datalen;
+
+	case MLXCPLD_LPCI2C_NACK_IND:
+		return -ENXIO;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static void mlxcpld_i2c_xfer_msg(struct mlxcpld_i2c_priv *priv)
+{
+	int i, len = 0;
+	u8 cmd;
+
+	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_NUM_DAT_REG,
+			       &priv->xfer.data_len, 1);
+	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_NUM_ADDR_REG,
+			       &priv->xfer.addr_width, 1);
+
+	for (i = 0; i < priv->xfer.msg_num; i++) {
+		if ((priv->xfer.msg[i].flags & I2C_M_RD) != I2C_M_RD) {
+			/* Don't write to CPLD buffer in read transaction */
+			mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_DATA_REG +
+					       len, priv->xfer.msg[i].buf,
+					       priv->xfer.msg[i].len);
+			len += priv->xfer.msg[i].len;
+		}
+	}
+
+	/*
+	 * Set target slave address with command for master transfer.
+	 * It should be latest executed function before CPLD transaction.
+	 */
+	cmd = (priv->xfer.msg[0].addr << 1) | priv->xfer.cmd;
+	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_CMD_REG, &cmd, 1);
+}
+
+/*
+ * Generic lpc-i2c transfer.
+ * Returns the number of processed messages or error (<0).
+ */
+static int mlxcpld_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+			    int num)
+{
+	struct mlxcpld_i2c_priv *priv = i2c_get_adapdata(adap);
+	u8 comm_len = 0;
+	int i, err;
+
+	err = mlxcpld_i2c_check_msg_params(priv, msgs, num);
+	if (err) {
+		dev_err(priv->dev, "Incorrect message\n");
+		return err;
+	}
+
+	for (i = 0; i < num; ++i)
+		comm_len += msgs[i].len;
+
+	/* Check bus state */
+	if (mlxcpld_i2c_wait_for_free(priv)) {
+		dev_err(priv->dev, "LPCI2C bridge is busy\n");
+
+		/*
+		 * Usually it means something serious has happened.
+		 * We can not have unfinished previous transfer
+		 * so it doesn't make any sense to try to stop it.
+		 * Probably we were not able to recover from the
+		 * previous error.
+		 * The only reasonable thing - is soft reset.
+		 */
+		mlxcpld_i2c_reset(priv);
+		if (mlxcpld_i2c_check_busy(priv)) {
+			dev_err(priv->dev, "LPCI2C bridge is busy after reset\n");
+			return -EIO;
+		}
+	}
+
+	mlxcpld_i2c_set_transf_data(priv, msgs, num, comm_len);
+
+	mutex_lock(&priv->lock);
+
+	/* Do real transfer. Can't fail */
+	mlxcpld_i2c_xfer_msg(priv);
+
+	/* Wait for transaction complete */
+	err = mlxcpld_i2c_wait_for_tc(priv);
+
+	mutex_unlock(&priv->lock);
+
+	return err < 0 ? err : num;
+}
+
+static u32 mlxcpld_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_SMBUS_BLOCK_DATA;
+}
+
+static const struct i2c_algorithm mlxcpld_i2c_algo = {
+	.master_xfer	= mlxcpld_i2c_xfer,
+	.functionality	= mlxcpld_i2c_func
+};
+
+static struct i2c_adapter_quirks mlxcpld_i2c_quirks = {
+	.flags = I2C_AQ_COMB_WRITE_THEN_READ,
+	.max_read_len = MLXCPLD_I2C_DATA_REG_SZ - MLXCPLD_I2C_MAX_ADDR_LEN,
+	.max_write_len = MLXCPLD_I2C_DATA_REG_SZ,
+	.max_comb_1st_msg_len = 4,
+};
+
+static struct i2c_adapter mlxcpld_i2c_adapter = {
+	.owner          = THIS_MODULE,
+	.name           = "i2c-mlxcpld",
+	.class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
+	.algo           = &mlxcpld_i2c_algo,
+	.quirks		= &mlxcpld_i2c_quirks,
+	.retries	= MLXCPLD_I2C_RETR_NUM,
+	.nr		= MLXCPLD_I2C_BUS_NUM,
+};
+
+static int mlxcpld_i2c_probe(struct platform_device *pdev)
+{
+	struct mlxcpld_i2c_priv *priv;
+	int err;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	mutex_init(&priv->lock);
+	platform_set_drvdata(pdev, priv);
+
+	priv->dev = &pdev->dev;
+
+	/* Register with i2c layer */
+	mlxcpld_i2c_adapter.timeout = usecs_to_jiffies(MLXCPLD_I2C_XFER_TO);
+	priv->adap = mlxcpld_i2c_adapter;
+	priv->adap.dev.parent = &pdev->dev;
+	priv->base_addr = MLXPLAT_CPLD_LPC_I2C_BASE_ADDR;
+	i2c_set_adapdata(&priv->adap, priv);
+
+	err = i2c_add_numbered_adapter(&priv->adap);
+	if (err)
+		mutex_destroy(&priv->lock);
+
+	return err;
+}
+
+static int mlxcpld_i2c_remove(struct platform_device *pdev)
+{
+	struct mlxcpld_i2c_priv *priv = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&priv->adap);
+	mutex_destroy(&priv->lock);
+
+	return 0;
+}
+
+static struct platform_driver mlxcpld_i2c_driver = {
+	.probe		= mlxcpld_i2c_probe,
+	.remove		= mlxcpld_i2c_remove,
+	.driver = {
+		.name = MLXCPLD_I2C_DEVICE_NAME,
+	},
+};
+
+module_platform_driver(mlxcpld_i2c_driver);
+
+MODULE_AUTHOR("Michael Shych <michaels@...lanox.com>");
+MODULE_DESCRIPTION("Mellanox I2C-CPLD controller driver");
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS("platform:i2c-mlxcpld");
-- 
2.1.4

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