/*
   * Copyright (C) 2006-2007 PA Semi, Inc
   *
   * SMBus host driver for PA Semi PWRficient
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   */
  
  #include <linux/module.h>
  #include <linux/pci.h>
  #include <linux/kernel.h>
  #include <linux/stddef.h>
  #include <linux/sched.h>
  #include <linux/i2c.h>
  #include <linux/delay.h>
  #include <linux/slab.h>
  #include <linux/io.h>
  
  static struct pci_driver pasemi_smb_driver;
  
  struct pasemi_smbus {
  	struct pci_dev		*dev;
  	struct i2c_adapter	 adapter;
  	unsigned long		 base;
  	int			 size;
  };
  
  /* Register offsets */
  #define REG_MTXFIFO	0x00
  #define REG_MRXFIFO	0x04
  #define REG_SMSTA	0x14
  #define REG_CTL		0x1c
  
  /* Register defs */
  #define MTXFIFO_READ	0x00000400
  #define MTXFIFO_STOP	0x00000200
  #define MTXFIFO_START	0x00000100
  #define MTXFIFO_DATA_M	0x000000ff
  
  #define MRXFIFO_EMPTY	0x00000100
  #define MRXFIFO_DATA_M	0x000000ff
  
  #define SMSTA_XEN	0x08000000
  #define SMSTA_MTN	0x00200000
  
  #define CTL_MRR		0x00000400
  #define CTL_MTR		0x00000200
  #define CTL_CLK_M	0x000000ff
  
  #define CLK_100K_DIV	84
  #define CLK_400K_DIV	21
  
  static inline void reg_write(struct pasemi_smbus *smbus, int reg, int val)
  {
  	dev_dbg(&smbus->dev->dev, "smbus write reg %lx val %08x
  ",
  		smbus->base + reg, val);
  	outl(val, smbus->base + reg);
  }
  
  static inline int reg_read(struct pasemi_smbus *smbus, int reg)
  {
  	int ret;
  	ret = inl(smbus->base + reg);
  	dev_dbg(&smbus->dev->dev, "smbus read reg %lx val %08x
  ",
  		smbus->base + reg, ret);
  	return ret;
  }
  
  #define TXFIFO_WR(smbus, reg)	reg_write((smbus), REG_MTXFIFO, (reg))
  #define RXFIFO_RD(smbus)	reg_read((smbus), REG_MRXFIFO)
  
  static void pasemi_smb_clear(struct pasemi_smbus *smbus)
  {
  	unsigned int status;
  
  	status = reg_read(smbus, REG_SMSTA);
  	reg_write(smbus, REG_SMSTA, status);
  }
  
  static int pasemi_smb_waitready(struct pasemi_smbus *smbus)
  {
  	int timeout = 10;
  	unsigned int status;
  
  	status = reg_read(smbus, REG_SMSTA);
  
  	while (!(status & SMSTA_XEN) && timeout--) {
  		msleep(1);
  		status = reg_read(smbus, REG_SMSTA);
  	}
  
  	/* Got NACK? */
  	if (status & SMSTA_MTN)
  		return -ENXIO;
  
  	if (timeout < 0) {
  		dev_warn(&smbus->dev->dev, "Timeout, status 0x%08x
  ", status);
  		reg_write(smbus, REG_SMSTA, status);
  		return -ETIME;
  	}
  
  	/* Clear XEN */
  	reg_write(smbus, REG_SMSTA, SMSTA_XEN);
  
  	return 0;
  }
  
  static int pasemi_i2c_xfer_msg(struct i2c_adapter *adapter,
  			       struct i2c_msg *msg, int stop)
  {
  	struct pasemi_smbus *smbus = adapter->algo_data;
  	int read, i, err;
  	u32 rd;
  
  	read = msg->flags & I2C_M_RD ? 1 : 0;
  
  	TXFIFO_WR(smbus, MTXFIFO_START | (msg->addr << 1) | read);
  
  	if (read) {
  		TXFIFO_WR(smbus, msg->len | MTXFIFO_READ |
  				 (stop ? MTXFIFO_STOP : 0));
  
  		err = pasemi_smb_waitready(smbus);
  		if (err)
  			goto reset_out;
  
  		for (i = 0; i < msg->len; i++) {
  			rd = RXFIFO_RD(smbus);
  			if (rd & MRXFIFO_EMPTY) {
  				err = -ENODATA;
  				goto reset_out;
  			}
  			msg->buf[i] = rd & MRXFIFO_DATA_M;
  		}
  	} else {
  		for (i = 0; i < msg->len - 1; i++)
  			TXFIFO_WR(smbus, msg->buf[i]);
  
  		TXFIFO_WR(smbus, msg->buf[msg->len-1] |
  			  (stop ? MTXFIFO_STOP : 0));
  	}
  
  	return 0;
  
   reset_out:
  	reg_write(smbus, REG_CTL, (CTL_MTR | CTL_MRR |
  		  (CLK_100K_DIV & CTL_CLK_M)));
  	return err;
  }
  
  static int pasemi_i2c_xfer(struct i2c_adapter *adapter,
  			   struct i2c_msg *msgs, int num)
  {
  	struct pasemi_smbus *smbus = adapter->algo_data;
  	int ret, i;
  
  	pasemi_smb_clear(smbus);
  
  	ret = 0;
  
  	for (i = 0; i < num && !ret; i++)
  		ret = pasemi_i2c_xfer_msg(adapter, &msgs[i], (i == (num - 1)));
  
  	return ret ? ret : num;
  }
  
  static int pasemi_smb_xfer(struct i2c_adapter *adapter,
  		u16 addr, unsigned short flags, char read_write, u8 command,
  		int size, union i2c_smbus_data *data)
  {
  	struct pasemi_smbus *smbus = adapter->algo_data;
  	unsigned int rd;
  	int read_flag, err;
  	int len = 0, i;
  
  	/* All our ops take 8-bit shifted addresses */
  	addr <<= 1;
  	read_flag = read_write == I2C_SMBUS_READ;
  
  	pasemi_smb_clear(smbus);
  
  	switch (size) {
  	case I2C_SMBUS_QUICK:
  		TXFIFO_WR(smbus, addr | read_flag | MTXFIFO_START |
  			  MTXFIFO_STOP);
  		break;
  	case I2C_SMBUS_BYTE:
  		TXFIFO_WR(smbus, addr | read_flag | MTXFIFO_START);
  		if (read_write)
  			TXFIFO_WR(smbus, 1 | MTXFIFO_STOP | MTXFIFO_READ);
  		else
  			TXFIFO_WR(smbus, MTXFIFO_STOP | command);
  		break;
  	case I2C_SMBUS_BYTE_DATA:
  		TXFIFO_WR(smbus, addr | MTXFIFO_START);
  		TXFIFO_WR(smbus, command);
  		if (read_write) {
  			TXFIFO_WR(smbus, addr | I2C_SMBUS_READ | MTXFIFO_START);
  			TXFIFO_WR(smbus, 1 | MTXFIFO_READ | MTXFIFO_STOP);
  		} else {
  			TXFIFO_WR(smbus, MTXFIFO_STOP | data->byte);
  		}
  		break;
  	case I2C_SMBUS_WORD_DATA:
  		TXFIFO_WR(smbus, addr | MTXFIFO_START);
  		TXFIFO_WR(smbus, command);
  		if (read_write) {
  			TXFIFO_WR(smbus, addr | I2C_SMBUS_READ | MTXFIFO_START);
  			TXFIFO_WR(smbus, 2 | MTXFIFO_READ | MTXFIFO_STOP);
  		} else {
  			TXFIFO_WR(smbus, data->word & MTXFIFO_DATA_M);
  			TXFIFO_WR(smbus, MTXFIFO_STOP | (data->word >> 8));
  		}
  		break;
  	case I2C_SMBUS_BLOCK_DATA:
  		TXFIFO_WR(smbus, addr | MTXFIFO_START);
  		TXFIFO_WR(smbus, command);
  		if (read_write) {
  			TXFIFO_WR(smbus, addr | I2C_SMBUS_READ | MTXFIFO_START);
  			TXFIFO_WR(smbus, 1 | MTXFIFO_READ);
  			rd = RXFIFO_RD(smbus);
  			len = min_t(u8, (rd & MRXFIFO_DATA_M),
  				    I2C_SMBUS_BLOCK_MAX);
  			TXFIFO_WR(smbus, len | MTXFIFO_READ |
  					 MTXFIFO_STOP);
  		} else {
  			len = min_t(u8, data->block[0], I2C_SMBUS_BLOCK_MAX);
  			TXFIFO_WR(smbus, len);
  			for (i = 1; i < len; i++)
  				TXFIFO_WR(smbus, data->block[i]);
  			TXFIFO_WR(smbus, data->block[len] | MTXFIFO_STOP);
  		}
  		break;
  	case I2C_SMBUS_PROC_CALL:
  		read_write = I2C_SMBUS_READ;
  		TXFIFO_WR(smbus, addr | MTXFIFO_START);
  		TXFIFO_WR(smbus, command);
  		TXFIFO_WR(smbus, data->word & MTXFIFO_DATA_M);
  		TXFIFO_WR(smbus, (data->word >> 8) & MTXFIFO_DATA_M);
  		TXFIFO_WR(smbus, addr | I2C_SMBUS_READ | MTXFIFO_START);
  		TXFIFO_WR(smbus, 2 | MTXFIFO_STOP | MTXFIFO_READ);
  		break;
  	case I2C_SMBUS_BLOCK_PROC_CALL:
  		len = min_t(u8, data->block[0], I2C_SMBUS_BLOCK_MAX - 1);
  		read_write = I2C_SMBUS_READ;
  		TXFIFO_WR(smbus, addr | MTXFIFO_START);
  		TXFIFO_WR(smbus, command);
  		TXFIFO_WR(smbus, len);
  		for (i = 1; i <= len; i++)
  			TXFIFO_WR(smbus, data->block[i]);
  		TXFIFO_WR(smbus, addr | I2C_SMBUS_READ);
  		TXFIFO_WR(smbus, MTXFIFO_READ | 1);
  		rd = RXFIFO_RD(smbus);
  		len = min_t(u8, (rd & MRXFIFO_DATA_M),
  			    I2C_SMBUS_BLOCK_MAX - len);
  		TXFIFO_WR(smbus, len | MTXFIFO_READ | MTXFIFO_STOP);
  		break;
  
  	default:
  		dev_warn(&adapter->dev, "Unsupported transaction %d
  ", size);
  		return -EINVAL;
  	}
  
  	err = pasemi_smb_waitready(smbus);
  	if (err)
  		goto reset_out;
  
  	if (read_write == I2C_SMBUS_WRITE)
  		return 0;
  
  	switch (size) {
  	case I2C_SMBUS_BYTE:
  	case I2C_SMBUS_BYTE_DATA:
  		rd = RXFIFO_RD(smbus);
  		if (rd & MRXFIFO_EMPTY) {
  			err = -ENODATA;
  			goto reset_out;
  		}
  		data->byte = rd & MRXFIFO_DATA_M;
  		break;
  	case I2C_SMBUS_WORD_DATA:
  	case I2C_SMBUS_PROC_CALL:
  		rd = RXFIFO_RD(smbus);
  		if (rd & MRXFIFO_EMPTY) {
  			err = -ENODATA;
  			goto reset_out;
  		}
  		data->word = rd & MRXFIFO_DATA_M;
  		rd = RXFIFO_RD(smbus);
  		if (rd & MRXFIFO_EMPTY) {
  			err = -ENODATA;
  			goto reset_out;
  		}
  		data->word |= (rd & MRXFIFO_DATA_M) << 8;
  		break;
  	case I2C_SMBUS_BLOCK_DATA:
  	case I2C_SMBUS_BLOCK_PROC_CALL:
  		data->block[0] = len;
  		for (i = 1; i <= len; i ++) {
  			rd = RXFIFO_RD(smbus);
  			if (rd & MRXFIFO_EMPTY) {
  				err = -ENODATA;
  				goto reset_out;
  			}
  			data->block[i] = rd & MRXFIFO_DATA_M;
  		}
  		break;
  	}
  
  	return 0;
  
   reset_out:
  	reg_write(smbus, REG_CTL, (CTL_MTR | CTL_MRR |
  		  (CLK_100K_DIV & CTL_CLK_M)));
  	return err;
  }
  
  static u32 pasemi_smb_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_BLOCK_DATA | I2C_FUNC_SMBUS_PROC_CALL |
  	       I2C_FUNC_SMBUS_BLOCK_PROC_CALL | I2C_FUNC_I2C;
  }
  
  static const struct i2c_algorithm smbus_algorithm = {
  	.master_xfer	= pasemi_i2c_xfer,
  	.smbus_xfer	= pasemi_smb_xfer,
  	.functionality	= pasemi_smb_func,
  };
  
  static int pasemi_smb_probe(struct pci_dev *dev,
  				      const struct pci_device_id *id)
  {
  	struct pasemi_smbus *smbus;
  	int error;
  
  	if (!(pci_resource_flags(dev, 0) & IORESOURCE_IO))
  		return -ENODEV;
  
  	smbus = kzalloc(sizeof(struct pasemi_smbus), GFP_KERNEL);
  	if (!smbus)
  		return -ENOMEM;
  
  	smbus->dev = dev;
  	smbus->base = pci_resource_start(dev, 0);
  	smbus->size = pci_resource_len(dev, 0);
  
  	if (!request_region(smbus->base, smbus->size,
  			    pasemi_smb_driver.name)) {
  		error = -EBUSY;
  		goto out_kfree;
  	}
  
  	smbus->adapter.owner = THIS_MODULE;
  	snprintf(smbus->adapter.name, sizeof(smbus->adapter.name),
  		 "PA Semi SMBus adapter at 0x%lx", smbus->base);
  	smbus->adapter.class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
  	smbus->adapter.algo = &smbus_algorithm;
  	smbus->adapter.algo_data = smbus;
  	smbus->adapter.nr = PCI_FUNC(dev->devfn);
  
  	/* set up the sysfs linkage to our parent device */
  	smbus->adapter.dev.parent = &dev->dev;
  
  	reg_write(smbus, REG_CTL, (CTL_MTR | CTL_MRR |
  		  (CLK_100K_DIV & CTL_CLK_M)));
  
  	error = i2c_add_numbered_adapter(&smbus->adapter);
  	if (error)
  		goto out_release_region;
  
  	pci_set_drvdata(dev, smbus);
  
  	return 0;
  
   out_release_region:
  	release_region(smbus->base, smbus->size);
   out_kfree:
  	kfree(smbus);
  	return error;
  }
  
  static void pasemi_smb_remove(struct pci_dev *dev)
  {
  	struct pasemi_smbus *smbus = pci_get_drvdata(dev);
  
  	i2c_del_adapter(&smbus->adapter);
  	release_region(smbus->base, smbus->size);
  	kfree(smbus);
  }
  
  static const struct pci_device_id pasemi_smb_ids[] = {
  	{ PCI_DEVICE(0x1959, 0xa003) },
  	{ 0, }
  };
  
  MODULE_DEVICE_TABLE(pci, pasemi_smb_ids);
  
  static struct pci_driver pasemi_smb_driver = {
  	.name		= "i2c-pasemi",
  	.id_table	= pasemi_smb_ids,
  	.probe		= pasemi_smb_probe,
  	.remove		= pasemi_smb_remove,
  };
  
  module_pci_driver(pasemi_smb_driver);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR ("Olof Johansson <olof@lixom.net>");
  MODULE_DESCRIPTION("PA Semi PWRficient SMBus driver");