/*
    atxp1.c - kernel module for setting CPU VID and general purpose
                     I/Os using the Attansic ATXP1 chip.

    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.

    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.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/i2c-sensor.h>
#include <linux/i2c-vid.h>

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("System voltages control via Attansic ATXP1");
MODULE_VERSION("0.6.2");
MODULE_AUTHOR("Sebastian Witt <se.witt@gmx.net>");

#define ATXP1_VID	0x00
#define ATXP1_CVID	0x01
#define ATXP1_GPIO1	0x06
#define ATXP1_GPIO2	0x0a
#define ATXP1_VIDENA	0x20
#define ATXP1_VIDMASK	0x1f
#define ATXP1_GPIO1MASK	0x0f

static unsigned short normal_i2c[] = { 0x37, 0x4e, I2C_CLIENT_END };
static unsigned int normal_isa[] = { I2C_CLIENT_ISA_END };

SENSORS_INSMOD_1(atxp1);

static int atxp1_attach_adapter(struct i2c_adapter * adapter);
static int atxp1_detach_client(struct i2c_client * client);
static struct atxp1_data * atxp1_update_device(struct device *dev);
static int atxp1_detect(struct i2c_adapter *adapter, int address, int kind);

static struct i2c_driver atxp1_driver = {
	.owner		= THIS_MODULE,
	.name		= "atxp1",
	.flags		= I2C_DF_NOTIFY,
	.attach_adapter = atxp1_attach_adapter,
	.detach_client	= atxp1_detach_client,
};

struct atxp1_data {
	struct i2c_client client;
	struct semaphore update_lock;
	unsigned long last_updated;
	u8 valid;
	struct {
		u8 vid;		/* VID output register */
		u8 cpu_vid; /* VID input from CPU */
		u8 gpio1;   /* General purpose I/O register 1 */
		u8 gpio2;   /* General purpose I/O register 2 */
	} reg;
	u8 vrm;			/* Detected CPU VRM */
};

static struct atxp1_data * atxp1_update_device(struct device *dev)
{
	struct i2c_client *client;
	struct atxp1_data *data;

	client = to_i2c_client(dev);
	data = i2c_get_clientdata(client);

	down(&data->update_lock);

	if ((jiffies - data->last_updated > HZ) ||
	    (jiffies < data->last_updated) ||
	    !data->valid) {

		/* Update local register data */
		data->reg.vid = i2c_smbus_read_byte_data(client, ATXP1_VID);
		data->reg.cpu_vid = i2c_smbus_read_byte_data(client, ATXP1_CVID);
		data->reg.gpio1 = i2c_smbus_read_byte_data(client, ATXP1_GPIO1);
		data->reg.gpio2 = i2c_smbus_read_byte_data(client, ATXP1_GPIO2);

		data->valid = 1;
	}

	up(&data->update_lock);

	return(data);
}

/* sys file functions for cpu0_vid */
static ssize_t atxp1_showvcore(struct device *dev, char *buf)
{
	int size;
	struct atxp1_data *data;

	data = atxp1_update_device(dev);

	size = sprintf(buf, "%d\n", vid_from_reg(data->reg.vid & ATXP1_VIDMASK, data->vrm));

	return size;
}

static ssize_t atxp1_storevcore(struct device *dev, const char* buf, size_t count)
{
	struct atxp1_data *data;
	struct i2c_client *client;
	char vid;
	char cvid;
	unsigned int vcore;

	client = to_i2c_client(dev);
	data = atxp1_update_device(dev);

	vcore = simple_strtoul(buf, NULL, 10);
	vcore /= 25;
	vcore *= 25;

	/* Calculate VID */
	vid = vid_to_reg(vcore, data->vrm);

	if (vid < 0) {
		dev_err(dev, "VID calculation failed.\n");
		return -1;
	}

	/* If output enabled, use control register value. Otherwise original CPU VID */
	if (data->reg.vid & ATXP1_VIDENA)
		cvid = data->reg.vid & ATXP1_VIDMASK;
	else
		cvid = data->reg.cpu_vid;

	/* Nothing changed, aborting */
	if (vid == cvid)
		return count;

	dev_info(dev, "Setting VCore to %d mV (0x%02x)\n", vcore, vid);

	/* Write every 25 mV step to increase stability */
	if (cvid > vid) {
		for (; cvid >= vid; cvid--) {
        		i2c_smbus_write_byte_data(client, ATXP1_VID, cvid | ATXP1_VIDENA);
		}
	}
	else {
		for (; cvid <= vid; cvid++) {
        		i2c_smbus_write_byte_data(client, ATXP1_VID, cvid | ATXP1_VIDENA);
		}
	}

	data->valid = 0;

	return count;
}

/* CPU core reference voltage
    unit: millivolt
*/
static DEVICE_ATTR(cpu0_vid, S_IRUGO | S_IWUSR, atxp1_showvcore, atxp1_storevcore);

/* sys file functions for GPIO1 */
static ssize_t atxp1_showgpio1(struct device *dev, char *buf)
{
	int size;
	struct atxp1_data *data;

	data = atxp1_update_device(dev);

	size = sprintf(buf, "0x%02x\n", data->reg.gpio1 & ATXP1_GPIO1MASK);

	return size;
}

static ssize_t atxp1_storegpio1(struct device *dev, const char* buf, size_t count)
{
	struct atxp1_data *data;
	struct i2c_client *client;
	unsigned int value;

	client = to_i2c_client(dev);
	data = atxp1_update_device(dev);

	value = simple_strtoul(buf, NULL, 16);

	value &= ATXP1_GPIO1MASK;

	if (value != (data->reg.gpio1 & ATXP1_GPIO1MASK)) {
		dev_info(dev, "Writing 0x%x to GPIO1.\n", value);

		i2c_smbus_write_byte_data(client, ATXP1_GPIO1, value);

		data->valid = 0;
	}

	return count;
}

/* GPIO1 data register
    unit: Four bit as hex (e.g. 0x0f)
*/
static DEVICE_ATTR(gpio1, S_IRUGO | S_IWUSR, atxp1_showgpio1, atxp1_storegpio1);

/* sys file functions for GPIO2 */
static ssize_t atxp1_showgpio2(struct device *dev, char *buf)
{
	int size;
	struct atxp1_data *data;

	data = atxp1_update_device(dev);

	size = sprintf(buf, "0x%02x\n", data->reg.gpio2);

	return size;
}

static ssize_t atxp1_storegpio2(struct device *dev, const char* buf, size_t count)
{
	struct atxp1_data *data;
	struct i2c_client *client;
	unsigned int value;

	client = to_i2c_client(dev);
	data = atxp1_update_device(dev);

	value = simple_strtoul(buf, NULL, 16) & 0xff;

	if (value != data->reg.gpio2) {
		dev_info(dev, "Writing 0x%x to GPIO1.\n", value);

		i2c_smbus_write_byte_data(client, ATXP1_GPIO2, value);

		data->valid = 0;
	}

	return count;
}

/* GPIO2 data register
    unit: Eight bit as hex (e.g. 0xff)
*/
static DEVICE_ATTR(gpio2, S_IRUGO | S_IWUSR, atxp1_showgpio2, atxp1_storegpio2);


static int atxp1_attach_adapter(struct i2c_adapter *adapter)
{
	return i2c_detect(adapter, &addr_data, &atxp1_detect);
};

static int atxp1_detect(struct i2c_adapter *adapter, int address, int kind)
{
	struct i2c_client * new_client;
	struct atxp1_data * data;
	int err = 0;
	u8 temp;

	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
		goto exit;

	if (!(data = kmalloc(sizeof(struct atxp1_data), GFP_KERNEL))) {
		err = -ENOMEM;
		goto exit;
	}

	memset(data, 0, sizeof(struct atxp1_data));
	new_client = &data->client;
	i2c_set_clientdata(new_client, data);

	new_client->addr = address;
	new_client->adapter = adapter;
	new_client->driver = &atxp1_driver;
	new_client->flags = 0;

	/* Detect ATXP1, checking if vendor ID registers are all zero */
	if (!((i2c_smbus_read_byte_data(new_client, 0x3e) == 0) &&
	     (i2c_smbus_read_byte_data(new_client, 0x3f) == 0) &&
	     (i2c_smbus_read_byte_data(new_client, 0xfe) == 0) &&
	     (i2c_smbus_read_byte_data(new_client, 0xff) == 0) )) {

		/* No vendor ID, now checking if registers 0x10,0x11 (non-existent)
		 * showing the same as register 0x00 */
		temp = i2c_smbus_read_byte_data(new_client, 0x00);

		if (!((i2c_smbus_read_byte_data(new_client, 0x10) == temp) &&
			 (i2c_smbus_read_byte_data(new_client, 0x11) == temp) ))
			goto exit_free;
	}

	/* Get VRM */
	data->vrm = i2c_which_vrm();

	if ((data->vrm != 90) && (data->vrm != 91)) {
		dev_err(&new_client->dev, "Not supporting VRM %d.%d\n",
				data->vrm / 10, data->vrm % 10);
		goto exit_free;
	}

	strncpy(new_client->name, "atxp1", I2C_NAME_SIZE);

	data->valid = 0;

	init_MUTEX(&data->update_lock);

	err = i2c_attach_client(new_client);

	if (err)
	{
		dev_err(&new_client->dev, "Attach client error.\n");
		goto exit_free;
	}

	device_create_file(&new_client->dev, &dev_attr_gpio1);
	device_create_file(&new_client->dev, &dev_attr_gpio2);
	device_create_file(&new_client->dev, &dev_attr_cpu0_vid);

	dev_info(&new_client->dev, "Using VRM: %d.%d\n",
			 data->vrm / 10, data->vrm % 10);

	return 0;

exit_free:
	kfree(data);
exit:
	return err;
};

static int atxp1_detach_client(struct i2c_client * client)
{
	int err;

	err = i2c_detach_client(client);

	if (err)
		dev_err(&client->dev, "Failed to detach client.\n");
	else
		kfree(i2c_get_clientdata(client));

	return err;
};

static int __init atxp1_init(void)
{
	return i2c_add_driver(&atxp1_driver);
};

static void __exit atxp1_exit(void)
{
	i2c_del_driver(&atxp1_driver);
};

module_init(atxp1_init);
module_exit(atxp1_exit);