drivers/i2c/busses/scx200_acb.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
     Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>

     National Semiconductor SCx200 ACCESS.bus support
     Also supports the AMD CS5535 and AMD CS5536

     Based on i2c-keywest.c which is:
         Copyright (c) 2001 Benjamin Herrenschmidt <benh@kernel.crashing.org>
         Copyright (c) 2000 Philip Edelbrock <phil@stimpy.netroedge.com>

 */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/module.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/i2c.h>
 #include <linux/pci.h>
 #include <linux/platform_device.h>
 #include <linux/delay.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/io.h>

 #include <linux/scx200.h>

 MODULE_AUTHOR("Christer Weinigel <wingel@nano-system.com>");
 MODULE_DESCRIPTION("NatSemi SCx200 ACCESS.bus Driver");
 MODULE_ALIAS("platform:cs5535-smb");
 MODULE_LICENSE("GPL");

 #define MAX_DEVICES 4
 static int base[MAX_DEVICES] = { 0x820, 0x840 };
 module_param_hw_array(base, int, ioport, NULL, 0);
 MODULE_PARM_DESC(base, "Base addresses for the ACCESS.bus controllers");

 #define POLL_TIMEOUT	(HZ/5)

 enum scx200_acb_state {
 	state_idle,
 	state_address,
 	state_command,
 	state_repeat_start,
 	state_quick,
 	state_read,
 	state_write,
 };

 static const char *scx200_acb_state_name[] = {
 	"idle",
 	"address",
 	"command",
 	"repeat_start",
 	"quick",
 	"read",
 	"write",
 };

 /* Physical interface */
 struct scx200_acb_iface {
 	struct scx200_acb_iface *next;
 	struct i2c_adapter adapter;
 	unsigned base;
 	struct mutex mutex;

 	/* State machine data */
 	enum scx200_acb_state state;
 	int result;
 	u8 address_byte;
 	u8 command;
 	u8 *ptr;
 	char needs_reset;
 	unsigned len;
 };

 /* Register Definitions */
 #define ACBSDA		(iface->base + 0)
 #define ACBST		(iface->base + 1)
 #define    ACBST_SDAST		0x40 /* SDA Status */
 #define    ACBST_BER		0x20
 #define    ACBST_NEGACK		0x10 /* Negative Acknowledge */
 #define    ACBST_STASTR		0x08 /* Stall After Start */
 #define    ACBST_MASTER		0x02
 #define ACBCST		(iface->base + 2)
 #define    ACBCST_BB		0x02
 #define ACBCTL1		(iface->base + 3)
 #define    ACBCTL1_STASTRE	0x80
 #define    ACBCTL1_NMINTE	0x40
 #define    ACBCTL1_ACK		0x10
 #define    ACBCTL1_STOP		0x02
 #define    ACBCTL1_START	0x01
 #define ACBADDR		(iface->base + 4)
 #define ACBCTL2		(iface->base + 5)
 #define    ACBCTL2_ENABLE	0x01

 /************************************************************************/

 static void scx200_acb_machine(struct scx200_acb_iface *iface, u8 status)
 {
 	const char *errmsg;

 	dev_dbg(&iface->adapter.dev, "state %s, status = 0x%02x\n",
 		scx200_acb_state_name[iface->state], status);

 	if (status & ACBST_BER) {
 		errmsg = "bus error";
 		goto error;
 	}
 	if (!(status & ACBST_MASTER)) {
 		errmsg = "not master";
 		goto error;
 	}
 	if (status & ACBST_NEGACK) {
 		dev_dbg(&iface->adapter.dev, "negative ack in state %s\n",
 			scx200_acb_state_name[iface->state]);

 		iface->state = state_idle;
 		iface->result = -ENXIO;

 		outb(inb(ACBCTL1) | ACBCTL1_STOP, ACBCTL1);
 		outb(ACBST_STASTR | ACBST_NEGACK, ACBST);

 		/* Reset the status register */
 		outb(0, ACBST);
 		return;
 	}

 	switch (iface->state) {
 	case state_idle:
 		dev_warn(&iface->adapter.dev, "interrupt in idle state\n");
 		break;

 	case state_address:
 		/* Do a pointer write first */
 		outb(iface->address_byte & ~1, ACBSDA);

 		iface->state = state_command;
 		break;

 	case state_command:
 		outb(iface->command, ACBSDA);

 		if (iface->address_byte & 1)
 			iface->state = state_repeat_start;
 		else
 			iface->state = state_write;
 		break;

 	case state_repeat_start:
 		outb(inb(ACBCTL1) | ACBCTL1_START, ACBCTL1);
 		fallthrough;

 	case state_quick:
 		if (iface->address_byte & 1) {
 			if (iface->len == 1)
 				outb(inb(ACBCTL1) | ACBCTL1_ACK, ACBCTL1);
 			else
 				outb(inb(ACBCTL1) & ~ACBCTL1_ACK, ACBCTL1);
 			outb(iface->address_byte, ACBSDA);

 			iface->state = state_read;
 		} else {
 			outb(iface->address_byte, ACBSDA);

 			iface->state = state_write;
 		}
 		break;

 	case state_read:
 		/* Set ACK if _next_ byte will be the last one */
 		if (iface->len == 2)
 			outb(inb(ACBCTL1) | ACBCTL1_ACK, ACBCTL1);
 		else
 			outb(inb(ACBCTL1) & ~ACBCTL1_ACK, ACBCTL1);

 		if (iface->len == 1) {
 			iface->result = 0;
 			iface->state = state_idle;
 			outb(inb(ACBCTL1) | ACBCTL1_STOP, ACBCTL1);
 		}

 		*iface->ptr++ = inb(ACBSDA);
 		--iface->len;

 		break;

 	case state_write:
 		if (iface->len == 0) {
 			iface->result = 0;
 			iface->state = state_idle;
 			outb(inb(ACBCTL1) | ACBCTL1_STOP, ACBCTL1);
 			break;
 		}

 		outb(*iface->ptr++, ACBSDA);
 		--iface->len;

 		break;
 	}

 	return;

  error:
 	dev_err(&iface->adapter.dev,
 		"%s in state %s (addr=0x%02x, len=%d, status=0x%02x)\n", errmsg,
 		scx200_acb_state_name[iface->state], iface->address_byte,
 		iface->len, status);

 	iface->state = state_idle;
 	iface->result = -EIO;
 	iface->needs_reset = 1;
 }

 static void scx200_acb_poll(struct scx200_acb_iface *iface)
 {
 	u8 status;
 	unsigned long timeout;

 	timeout = jiffies + POLL_TIMEOUT;
 	while (1) {
 		status = inb(ACBST);

 		/* Reset the status register to avoid the hang */
 		outb(0, ACBST);

 		if ((status & (ACBST_SDAST|ACBST_BER|ACBST_NEGACK)) != 0) {
 			scx200_acb_machine(iface, status);
 			return;
 		}
 		if (time_after(jiffies, timeout))
 			break;
 		cpu_relax();
 		cond_resched();
 	}

 	dev_err(&iface->adapter.dev, "timeout in state %s\n",
 		scx200_acb_state_name[iface->state]);

 	iface->state = state_idle;
 	iface->result = -EIO;
 	iface->needs_reset = 1;
 }

 static void scx200_acb_reset(struct scx200_acb_iface *iface)
 {
 	/* Disable the ACCESS.bus device and Configure the SCL
 	   frequency: 16 clock cycles */
 	outb(0x70, ACBCTL2);
 	/* Polling mode */
 	outb(0, ACBCTL1);
 	/* Disable slave address */
 	outb(0, ACBADDR);
 	/* Enable the ACCESS.bus device */
 	outb(inb(ACBCTL2) | ACBCTL2_ENABLE, ACBCTL2);
 	/* Free STALL after START */
 	outb(inb(ACBCTL1) & ~(ACBCTL1_STASTRE | ACBCTL1_NMINTE), ACBCTL1);
 	/* Send a STOP */
 	outb(inb(ACBCTL1) | ACBCTL1_STOP, ACBCTL1);
 	/* Clear BER, NEGACK and STASTR bits */
 	outb(ACBST_BER | ACBST_NEGACK | ACBST_STASTR, ACBST);
 	/* Clear BB bit */
 	outb(inb(ACBCST) | ACBCST_BB, ACBCST);
 }

 static s32 scx200_acb_smbus_xfer(struct i2c_adapter *adapter,
 				 u16 address, unsigned short flags,
 				 char rw, u8 command, int size,
 				 union i2c_smbus_data *data)
 {
 	struct scx200_acb_iface *iface = i2c_get_adapdata(adapter);
 	int len;
 	u8 *buffer;
 	u16 cur_word;
 	int rc;

 	switch (size) {
 	case I2C_SMBUS_QUICK:
 		len = 0;
 		buffer = NULL;
 		break;

 	case I2C_SMBUS_BYTE:
 		len = 1;
 		buffer = rw ? &data->byte : &command;
 		break;

 	case I2C_SMBUS_BYTE_DATA:
 		len = 1;
 		buffer = &data->byte;
 		break;

 	case I2C_SMBUS_WORD_DATA:
 		len = 2;
 		cur_word = cpu_to_le16(data->word);
 		buffer = (u8 *)&cur_word;
 		break;

 	case I2C_SMBUS_I2C_BLOCK_DATA:
 		len = data->block[0];
 		if (len == 0 || len > I2C_SMBUS_BLOCK_MAX)
 			return -EINVAL;
 		buffer = &data->block[1];
 		break;

 	default:
 		return -EINVAL;
 	}

 	dev_dbg(&adapter->dev,
 		"size=%d, address=0x%x, command=0x%x, len=%d, read=%d\n",
 		size, address, command, len, rw);

 	if (!len && rw == I2C_SMBUS_READ) {
 		dev_dbg(&adapter->dev, "zero length read\n");
 		return -EINVAL;
 	}

 	mutex_lock(&iface->mutex);

 	iface->address_byte = (address << 1) | rw;
 	iface->command = command;
 	iface->ptr = buffer;
 	iface->len = len;
 	iface->result = -EINVAL;
 	iface->needs_reset = 0;

 	outb(inb(ACBCTL1) | ACBCTL1_START, ACBCTL1);

 	if (size == I2C_SMBUS_QUICK || size == I2C_SMBUS_BYTE)
 		iface->state = state_quick;
 	else
 		iface->state = state_address;

 	while (iface->state != state_idle)
 		scx200_acb_poll(iface);

 	if (iface->needs_reset)
 		scx200_acb_reset(iface);

 	rc = iface->result;

 	mutex_unlock(&iface->mutex);

 	if (rc == 0 && size == I2C_SMBUS_WORD_DATA && rw == I2C_SMBUS_READ)
 		data->word = le16_to_cpu(cur_word);

 #ifdef DEBUG
 	dev_dbg(&adapter->dev, "transfer done, result: %d", rc);
 	if (buffer) {
 		int i;
 		printk(" data:");
 		for (i = 0; i < len; ++i)
 			printk(" %02x", buffer[i]);
 	}
 	printk("\n");
 #endif

 	return rc;
 }

 static u32 scx200_acb_func(struct i2c_adapter *adapter)
 {
 	return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
 	       I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
 	       I2C_FUNC_SMBUS_I2C_BLOCK;
 }

 /* For now, we only handle combined mode (smbus) */
 static const struct i2c_algorithm scx200_acb_algorithm = {
 	.smbus_xfer	= scx200_acb_smbus_xfer,
 	.functionality	= scx200_acb_func,
 };

 static struct scx200_acb_iface *scx200_acb_list;
 static DEFINE_MUTEX(scx200_acb_list_mutex);

 static int scx200_acb_probe(struct scx200_acb_iface *iface)
 {
 	u8 val;

 	/* Disable the ACCESS.bus device and Configure the SCL
 	   frequency: 16 clock cycles */
 	outb(0x70, ACBCTL2);

 	if (inb(ACBCTL2) != 0x70) {
 		pr_debug("ACBCTL2 readback failed\n");
 		return -ENXIO;
 	}

 	outb(inb(ACBCTL1) | ACBCTL1_NMINTE, ACBCTL1);

 	val = inb(ACBCTL1);
 	if (val) {
 		pr_debug("disabled, but ACBCTL1=0x%02x\n", val);
 		return -ENXIO;
 	}

 	outb(inb(ACBCTL2) | ACBCTL2_ENABLE, ACBCTL2);

 	outb(inb(ACBCTL1) | ACBCTL1_NMINTE, ACBCTL1);

 	val = inb(ACBCTL1);
 	if ((val & ACBCTL1_NMINTE) != ACBCTL1_NMINTE) {
 		pr_debug("enabled, but NMINTE won't be set, ACBCTL1=0x%02x\n",
 			 val);
 		return -ENXIO;
 	}

 	return 0;
 }

 static struct scx200_acb_iface *scx200_create_iface(const char *text,
 		struct device *dev, int index)
 {
 	struct scx200_acb_iface *iface;
 	struct i2c_adapter *adapter;

 	iface = kzalloc(sizeof(*iface), GFP_KERNEL);
 	if (!iface)
 		return NULL;

 	adapter = &iface->adapter;
 	i2c_set_adapdata(adapter, iface);
 	snprintf(adapter->name, sizeof(adapter->name), "%s ACB%d", text, index);
 	adapter->owner = THIS_MODULE;
 	adapter->algo = &scx200_acb_algorithm;
 	adapter->class = I2C_CLASS_HWMON;
 	adapter->dev.parent = dev;

 	mutex_init(&iface->mutex);

 	return iface;
 }

 static int scx200_acb_create(struct scx200_acb_iface *iface)
 {
 	struct i2c_adapter *adapter;
 	int rc;

 	adapter = &iface->adapter;

 	rc = scx200_acb_probe(iface);
 	if (rc) {
 		pr_warn("probe failed\n");
 		return rc;
 	}

 	scx200_acb_reset(iface);

 	if (i2c_add_adapter(adapter) < 0) {
 		pr_err("failed to register\n");
 		return -ENODEV;
 	}

 	if (!adapter->dev.parent) {
 		/* If there's no dev, we're tracking (ISA) ifaces manually */
 		mutex_lock(&scx200_acb_list_mutex);
 		iface->next = scx200_acb_list;
 		scx200_acb_list = iface;
 		mutex_unlock(&scx200_acb_list_mutex);
 	}

 	return 0;
 }

 static struct scx200_acb_iface *scx200_create_dev(const char *text,
 		unsigned long base, int index, struct device *dev)
 {
 	struct scx200_acb_iface *iface;
 	int rc;

 	iface = scx200_create_iface(text, dev, index);

 	if (iface == NULL)
 		return NULL;

 	if (!request_region(base, 8, iface->adapter.name)) {
 		pr_err("can't allocate io 0x%lx-0x%lx\n", base, base + 8 - 1);
 		goto errout_free;
 	}

 	iface->base = base;
 	rc = scx200_acb_create(iface);

 	if (rc == 0)
 		return iface;

 	release_region(base, 8);
  errout_free:
 	kfree(iface);
 	return NULL;
 }

 static int scx200_probe(struct platform_device *pdev)
 {
 	struct scx200_acb_iface *iface;
 	struct resource *res;

 	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
 	if (!res) {
 		dev_err(&pdev->dev, "can't fetch device resource info\n");
 		return -ENODEV;
 	}

 	iface = scx200_create_dev("CS5535", res->start, 0, &pdev->dev);
 	if (!iface)
 		return -EIO;

 	dev_info(&pdev->dev, "SCx200 device '%s' registered\n",
 			iface->adapter.name);
 	platform_set_drvdata(pdev, iface);

 	return 0;
 }

 static void scx200_cleanup_iface(struct scx200_acb_iface *iface)
 {
 	i2c_del_adapter(&iface->adapter);
 	release_region(iface->base, 8);
 	kfree(iface);
 }

 static void scx200_remove(struct platform_device *pdev)
 {
 	struct scx200_acb_iface *iface;

 	iface = platform_get_drvdata(pdev);
 	scx200_cleanup_iface(iface);
 }

 static struct platform_driver scx200_pci_driver = {
 	.driver = {
 		.name = "cs5535-smb",
 	},
 	.probe = scx200_probe,
 	.remove_new = scx200_remove,
 };

 static const struct pci_device_id scx200_isa[] = {
 	{ PCI_DEVICE(PCI_VENDOR_ID_NS, PCI_DEVICE_ID_NS_SCx200_BRIDGE) },
 	{ PCI_DEVICE(PCI_VENDOR_ID_NS, PCI_DEVICE_ID_NS_SC1100_BRIDGE) },
 	{ 0, }
 };

 static __init void scx200_scan_isa(void)
 {
 	int i;

 	if (!pci_dev_present(scx200_isa))
 		return;

 	for (i = 0; i < MAX_DEVICES; ++i) {
 		if (base[i] == 0)
 			continue;

 		/* XXX: should we care about failures? */
 		scx200_create_dev("SCx200", base[i], i, NULL);
 	}
 }

 static int __init scx200_acb_init(void)
 {
 	pr_debug("NatSemi SCx200 ACCESS.bus Driver\n");

 	/* First scan for ISA-based devices */
 	scx200_scan_isa();	/* XXX: should we care about errors? */

 	/* If at least one bus was created, init must succeed */
 	if (scx200_acb_list)
 		return 0;

 	/* No ISA devices; register the platform driver for PCI-based devices */
 	return platform_driver_register(&scx200_pci_driver);
 }

 static void __exit scx200_acb_cleanup(void)
 {
 	struct scx200_acb_iface *iface;

 	platform_driver_unregister(&scx200_pci_driver);

 	mutex_lock(&scx200_acb_list_mutex);
 	while ((iface = scx200_acb_list) != NULL) {
 		scx200_acb_list = iface->next;
 		mutex_unlock(&scx200_acb_list_mutex);

 		scx200_cleanup_iface(iface);

 		mutex_lock(&scx200_acb_list_mutex);
 	}
 	mutex_unlock(&scx200_acb_list_mutex);
 }

 module_init(scx200_acb_init);
 module_exit(scx200_acb_cleanup);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>

	National Semiconductor SCx200 ACCESS.bus support
	Also supports the AMD CS5535 and AMD CS5536

	Based on i2c-keywest.c which is:
	Copyright (c) 2001 Benjamin Herrenschmidt <benh@kernel.crashing.org>
	Copyright (c) 2000 Philip Edelbrock <phil@stimpy.netroedge.com>

	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/module.h>
	#include <linux/errno.h>
	#include <linux/kernel.h>
	#include <linux/init.h>
	#include <linux/i2c.h>
	#include <linux/pci.h>
	#include <linux/platform_device.h>
	#include <linux/delay.h>
	#include <linux/mutex.h>
	#include <linux/slab.h>
	#include <linux/io.h>

	#include <linux/scx200.h>

	MODULE_AUTHOR("Christer Weinigel <wingel@nano-system.com>");
	MODULE_DESCRIPTION("NatSemi SCx200 ACCESS.bus Driver");
	MODULE_ALIAS("platform:cs5535-smb");
	MODULE_LICENSE("GPL");

	#define MAX_DEVICES 4
	static int base[MAX_DEVICES] = { 0x820, 0x840 };
	module_param_hw_array(base, int, ioport, NULL, 0);
	MODULE_PARM_DESC(base, "Base addresses for the ACCESS.bus controllers");

	#define POLL_TIMEOUT (HZ/5)

	enum scx200_acb_state {
	state_idle,
	state_address,
	state_command,
	state_repeat_start,
	state_quick,
	state_read,
	state_write,
	};

	static const char *scx200_acb_state_name[] = {
	"idle",
	"address",
	"command",
	"repeat_start",
	"quick",
	"read",
	"write",
	};

	/* Physical interface */
	struct scx200_acb_iface {
	struct scx200_acb_iface *next;
	struct i2c_adapter adapter;
	unsigned base;
	struct mutex mutex;

	/* State machine data */
	enum scx200_acb_state state;
	int result;
	u8 address_byte;
	u8 command;
	u8 *ptr;
	char needs_reset;
	unsigned len;
	};

	/* Register Definitions */
	#define ACBSDA (iface->base + 0)
	#define ACBST (iface->base + 1)
	#define ACBST_SDAST 0x40 /* SDA Status */
	#define ACBST_BER 0x20
	#define ACBST_NEGACK 0x10 /* Negative Acknowledge */
	#define ACBST_STASTR 0x08 /* Stall After Start */
	#define ACBST_MASTER 0x02
	#define ACBCST (iface->base + 2)
	#define ACBCST_BB 0x02
	#define ACBCTL1 (iface->base + 3)
	#define ACBCTL1_STASTRE 0x80
	#define ACBCTL1_NMINTE 0x40
	#define ACBCTL1_ACK 0x10
	#define ACBCTL1_STOP 0x02
	#define ACBCTL1_START 0x01
	#define ACBADDR (iface->base + 4)
	#define ACBCTL2 (iface->base + 5)
	#define ACBCTL2_ENABLE 0x01

	/************************************************************************/

	static void scx200_acb_machine(struct scx200_acb_iface *iface, u8 status)
	{
	const char *errmsg;

	dev_dbg(&iface->adapter.dev, "state %s, status = 0x%02x\n",
	scx200_acb_state_name[iface->state], status);

	if (status & ACBST_BER) {
	errmsg = "bus error";
	goto error;
	}
	if (!(status & ACBST_MASTER)) {
	errmsg = "not master";
	goto error;
	}
	if (status & ACBST_NEGACK) {
	dev_dbg(&iface->adapter.dev, "negative ack in state %s\n",
	scx200_acb_state_name[iface->state]);

	iface->state = state_idle;
	iface->result = -ENXIO;

	outb(inb(ACBCTL1) \| ACBCTL1_STOP, ACBCTL1);
	outb(ACBST_STASTR \| ACBST_NEGACK, ACBST);

	/* Reset the status register */
	outb(0, ACBST);
	return;
	}

	switch (iface->state) {
	case state_idle:
	dev_warn(&iface->adapter.dev, "interrupt in idle state\n");
	break;

	case state_address:
	/* Do a pointer write first */
	outb(iface->address_byte & ~1, ACBSDA);

	iface->state = state_command;
	break;

	case state_command:
	outb(iface->command, ACBSDA);

	if (iface->address_byte & 1)
	iface->state = state_repeat_start;
	else
	iface->state = state_write;
	break;

	case state_repeat_start:
	outb(inb(ACBCTL1) \| ACBCTL1_START, ACBCTL1);
	fallthrough;

	case state_quick:
	if (iface->address_byte & 1) {
	if (iface->len == 1)
	outb(inb(ACBCTL1) \| ACBCTL1_ACK, ACBCTL1);
	else
	outb(inb(ACBCTL1) & ~ACBCTL1_ACK, ACBCTL1);
	outb(iface->address_byte, ACBSDA);

	iface->state = state_read;
	} else {
	outb(iface->address_byte, ACBSDA);

	iface->state = state_write;
	}
	break;

	case state_read:
	/* Set ACK if _next_ byte will be the last one */
	if (iface->len == 2)
	outb(inb(ACBCTL1) \| ACBCTL1_ACK, ACBCTL1);
	else
	outb(inb(ACBCTL1) & ~ACBCTL1_ACK, ACBCTL1);

	if (iface->len == 1) {
	iface->result = 0;
	iface->state = state_idle;
	outb(inb(ACBCTL1) \| ACBCTL1_STOP, ACBCTL1);
	}

	*iface->ptr++ = inb(ACBSDA);
	--iface->len;

	break;

	case state_write:
	if (iface->len == 0) {
	iface->result = 0;
	iface->state = state_idle;
	outb(inb(ACBCTL1) \| ACBCTL1_STOP, ACBCTL1);
	break;
	}

	outb(*iface->ptr++, ACBSDA);
	--iface->len;

	break;
	}

	return;

	error:
	dev_err(&iface->adapter.dev,
	"%s in state %s (addr=0x%02x, len=%d, status=0x%02x)\n", errmsg,
	scx200_acb_state_name[iface->state], iface->address_byte,
	iface->len, status);

	iface->state = state_idle;
	iface->result = -EIO;
	iface->needs_reset = 1;
	}

	static void scx200_acb_poll(struct scx200_acb_iface *iface)
	{
	u8 status;
	unsigned long timeout;

	timeout = jiffies + POLL_TIMEOUT;
	while (1) {
	status = inb(ACBST);

	/* Reset the status register to avoid the hang */
	outb(0, ACBST);

	if ((status & (ACBST_SDAST\|ACBST_BER\|ACBST_NEGACK)) != 0) {
	scx200_acb_machine(iface, status);
	return;
	}
	if (time_after(jiffies, timeout))
	break;
	cpu_relax();
	cond_resched();
	}

	dev_err(&iface->adapter.dev, "timeout in state %s\n",
	scx200_acb_state_name[iface->state]);

	iface->state = state_idle;
	iface->result = -EIO;
	iface->needs_reset = 1;
	}

	static void scx200_acb_reset(struct scx200_acb_iface *iface)
	{
	/* Disable the ACCESS.bus device and Configure the SCL
	frequency: 16 clock cycles */
	outb(0x70, ACBCTL2);
	/* Polling mode */
	outb(0, ACBCTL1);
	/* Disable slave address */
	outb(0, ACBADDR);
	/* Enable the ACCESS.bus device */
	outb(inb(ACBCTL2) \| ACBCTL2_ENABLE, ACBCTL2);
	/* Free STALL after START */
	outb(inb(ACBCTL1) & ~(ACBCTL1_STASTRE \| ACBCTL1_NMINTE), ACBCTL1);
	/* Send a STOP */
	outb(inb(ACBCTL1) \| ACBCTL1_STOP, ACBCTL1);
	/* Clear BER, NEGACK and STASTR bits */
	outb(ACBST_BER \| ACBST_NEGACK \| ACBST_STASTR, ACBST);
	/* Clear BB bit */
	outb(inb(ACBCST) \| ACBCST_BB, ACBCST);
	}

	static s32 scx200_acb_smbus_xfer(struct i2c_adapter *adapter,
	u16 address, unsigned short flags,
	char rw, u8 command, int size,
	union i2c_smbus_data *data)
	{
	struct scx200_acb_iface *iface = i2c_get_adapdata(adapter);
	int len;
	u8 *buffer;
	u16 cur_word;
	int rc;

	switch (size) {
	case I2C_SMBUS_QUICK:
	len = 0;
	buffer = NULL;
	break;

	case I2C_SMBUS_BYTE:
	len = 1;
	buffer = rw ? &data->byte : &command;
	break;

	case I2C_SMBUS_BYTE_DATA:
	len = 1;
	buffer = &data->byte;
	break;

	case I2C_SMBUS_WORD_DATA:
	len = 2;
	cur_word = cpu_to_le16(data->word);
	buffer = (u8 *)&cur_word;
	break;

	case I2C_SMBUS_I2C_BLOCK_DATA:
	len = data->block[0];
	if (len == 0 \|\| len > I2C_SMBUS_BLOCK_MAX)
	return -EINVAL;
	buffer = &data->block[1];
	break;

	default:
	return -EINVAL;
	}

	dev_dbg(&adapter->dev,
	"size=%d, address=0x%x, command=0x%x, len=%d, read=%d\n",
	size, address, command, len, rw);

	if (!len && rw == I2C_SMBUS_READ) {
	dev_dbg(&adapter->dev, "zero length read\n");
	return -EINVAL;
	}

	mutex_lock(&iface->mutex);

	iface->address_byte = (address << 1) \| rw;
	iface->command = command;
	iface->ptr = buffer;
	iface->len = len;
	iface->result = -EINVAL;
	iface->needs_reset = 0;

	outb(inb(ACBCTL1) \| ACBCTL1_START, ACBCTL1);

	if (size == I2C_SMBUS_QUICK \|\| size == I2C_SMBUS_BYTE)
	iface->state = state_quick;
	else
	iface->state = state_address;

	while (iface->state != state_idle)
	scx200_acb_poll(iface);

	if (iface->needs_reset)
	scx200_acb_reset(iface);

	rc = iface->result;

	mutex_unlock(&iface->mutex);

	if (rc == 0 && size == I2C_SMBUS_WORD_DATA && rw == I2C_SMBUS_READ)
	data->word = le16_to_cpu(cur_word);

	#ifdef DEBUG
	dev_dbg(&adapter->dev, "transfer done, result: %d", rc);
	if (buffer) {
	int i;
	printk(" data:");
	for (i = 0; i < len; ++i)
	printk(" %02x", buffer[i]);
	}
	printk("\n");
	#endif

	return rc;
	}

	static u32 scx200_acb_func(struct i2c_adapter *adapter)
	{
	return I2C_FUNC_SMBUS_QUICK \| I2C_FUNC_SMBUS_BYTE \|
	I2C_FUNC_SMBUS_BYTE_DATA \| I2C_FUNC_SMBUS_WORD_DATA \|
	I2C_FUNC_SMBUS_I2C_BLOCK;
	}

	/* For now, we only handle combined mode (smbus) */
	static const struct i2c_algorithm scx200_acb_algorithm = {
	.smbus_xfer = scx200_acb_smbus_xfer,
	.functionality = scx200_acb_func,
	};

	static struct scx200_acb_iface *scx200_acb_list;
	static DEFINE_MUTEX(scx200_acb_list_mutex);

	static int scx200_acb_probe(struct scx200_acb_iface *iface)
	{
	u8 val;

	/* Disable the ACCESS.bus device and Configure the SCL
	frequency: 16 clock cycles */
	outb(0x70, ACBCTL2);

	if (inb(ACBCTL2) != 0x70) {
	pr_debug("ACBCTL2 readback failed\n");
	return -ENXIO;
	}

	outb(inb(ACBCTL1) \| ACBCTL1_NMINTE, ACBCTL1);

	val = inb(ACBCTL1);
	if (val) {
	pr_debug("disabled, but ACBCTL1=0x%02x\n", val);
	return -ENXIO;
	}

	outb(inb(ACBCTL2) \| ACBCTL2_ENABLE, ACBCTL2);

	outb(inb(ACBCTL1) \| ACBCTL1_NMINTE, ACBCTL1);

	val = inb(ACBCTL1);
	if ((val & ACBCTL1_NMINTE) != ACBCTL1_NMINTE) {
	pr_debug("enabled, but NMINTE won't be set, ACBCTL1=0x%02x\n",
	val);
	return -ENXIO;
	}

	return 0;
	}

	static struct scx200_acb_iface scx200_create_iface(const char text,
	struct device *dev, int index)
	{
	struct scx200_acb_iface *iface;
	struct i2c_adapter *adapter;

	iface = kzalloc(sizeof(*iface), GFP_KERNEL);
	if (!iface)
	return NULL;

	adapter = &iface->adapter;
	i2c_set_adapdata(adapter, iface);
	snprintf(adapter->name, sizeof(adapter->name), "%s ACB%d", text, index);
	adapter->owner = THIS_MODULE;
	adapter->algo = &scx200_acb_algorithm;
	adapter->class = I2C_CLASS_HWMON;
	adapter->dev.parent = dev;

	mutex_init(&iface->mutex);

	return iface;
	}

	static int scx200_acb_create(struct scx200_acb_iface *iface)
	{
	struct i2c_adapter *adapter;
	int rc;

	adapter = &iface->adapter;

	rc = scx200_acb_probe(iface);
	if (rc) {
	pr_warn("probe failed\n");
	return rc;
	}

	scx200_acb_reset(iface);

	if (i2c_add_adapter(adapter) < 0) {
	pr_err("failed to register\n");
	return -ENODEV;
	}

	if (!adapter->dev.parent) {
	/* If there's no dev, we're tracking (ISA) ifaces manually */
	mutex_lock(&scx200_acb_list_mutex);
	iface->next = scx200_acb_list;
	scx200_acb_list = iface;
	mutex_unlock(&scx200_acb_list_mutex);
	}

	return 0;
	}

	static struct scx200_acb_iface scx200_create_dev(const char text,
	unsigned long base, int index, struct device *dev)
	{
	struct scx200_acb_iface *iface;
	int rc;

	iface = scx200_create_iface(text, dev, index);

	if (iface == NULL)
	return NULL;

	if (!request_region(base, 8, iface->adapter.name)) {
	pr_err("can't allocate io 0x%lx-0x%lx\n", base, base + 8 - 1);
	goto errout_free;
	}

	iface->base = base;
	rc = scx200_acb_create(iface);

	if (rc == 0)
	return iface;

	release_region(base, 8);
	errout_free:
	kfree(iface);
	return NULL;
	}

	static int scx200_probe(struct platform_device *pdev)
	{
	struct scx200_acb_iface *iface;
	struct resource *res;

	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
	if (!res) {
	dev_err(&pdev->dev, "can't fetch device resource info\n");
	return -ENODEV;
	}

	iface = scx200_create_dev("CS5535", res->start, 0, &pdev->dev);
	if (!iface)
	return -EIO;

	dev_info(&pdev->dev, "SCx200 device '%s' registered\n",
	iface->adapter.name);
	platform_set_drvdata(pdev, iface);

	return 0;
	}

	static void scx200_cleanup_iface(struct scx200_acb_iface *iface)
	{
	i2c_del_adapter(&iface->adapter);
	release_region(iface->base, 8);
	kfree(iface);
	}

	static void scx200_remove(struct platform_device *pdev)
	{
	struct scx200_acb_iface *iface;

	iface = platform_get_drvdata(pdev);
	scx200_cleanup_iface(iface);
	}

	static struct platform_driver scx200_pci_driver = {
	.driver = {
	.name = "cs5535-smb",
	},
	.probe = scx200_probe,
	.remove_new = scx200_remove,
	};

	static const struct pci_device_id scx200_isa[] = {
	{ PCI_DEVICE(PCI_VENDOR_ID_NS, PCI_DEVICE_ID_NS_SCx200_BRIDGE) },
	{ PCI_DEVICE(PCI_VENDOR_ID_NS, PCI_DEVICE_ID_NS_SC1100_BRIDGE) },
	{ 0, }
	};

	static __init void scx200_scan_isa(void)
	{
	int i;

	if (!pci_dev_present(scx200_isa))
	return;

	for (i = 0; i < MAX_DEVICES; ++i) {
	if (base[i] == 0)
	continue;

	/* XXX: should we care about failures? */
	scx200_create_dev("SCx200", base[i], i, NULL);
	}
	}

	static int __init scx200_acb_init(void)
	{
	pr_debug("NatSemi SCx200 ACCESS.bus Driver\n");

	/* First scan for ISA-based devices */
	scx200_scan_isa(); /* XXX: should we care about errors? */

	/* If at least one bus was created, init must succeed */
	if (scx200_acb_list)
	return 0;

	/* No ISA devices; register the platform driver for PCI-based devices */
	return platform_driver_register(&scx200_pci_driver);
	}

	static void __exit scx200_acb_cleanup(void)
	{
	struct scx200_acb_iface *iface;

	platform_driver_unregister(&scx200_pci_driver);

	mutex_lock(&scx200_acb_list_mutex);
	while ((iface = scx200_acb_list) != NULL) {
	scx200_acb_list = iface->next;
	mutex_unlock(&scx200_acb_list_mutex);

	scx200_cleanup_iface(iface);

	mutex_lock(&scx200_acb_list_mutex);
	}
	mutex_unlock(&scx200_acb_list_mutex);
	}

	module_init(scx200_acb_init);
	module_exit(scx200_acb_cleanup);