/*
 * 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/jiffies.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-vid.h>
#include <linux/err.h>
#include <linux/mutex.h>
#include <linux/sysfs.h>
#include <linux/slab.h>

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("System voltages control via Attansic ATXP1");
MODULE_VERSION("0.6.3");
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 const unsigned short normal_i2c[] = { 0x37, 0x4e, I2C_CLIENT_END };

static int atxp1_probe(struct i2c_client *client,
                       const struct i2c_device_id *id);
static int atxp1_remove(struct i2c_client *client);
static struct atxp1_data *atxp1_update_device(struct device *dev);
static int atxp1_detect(struct i2c_client *client, struct i2c_board_info *info);

static const struct i2c_device_id atxp1_id[] = {
        { "atxp1", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, atxp1_id);

static struct i2c_driver atxp1_driver = {
        .class          = I2C_CLASS_HWMON,
        .driver = {
                .name   = "atxp1",
        },
        .probe          = atxp1_probe,
        .remove         = atxp1_remove,
        .id_table       = atxp1_id,
        .detect         = atxp1_detect,
        .address_list   = normal_i2c,
};

struct atxp1_data {
        struct device *hwmon_dev;
        struct mutex 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);

        mutex_lock(&data->update_lock);

        if (time_after(jiffies, data->last_updated + HZ) || !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;
        }

        mutex_unlock(&data->update_lock);

        return data;
}

/* sys file functions for cpu0_vid */
static ssize_t atxp1_showvcore(struct device *dev,
                               struct device_attribute *attr, 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,
                                struct device_attribute *attr,
                                const char *buf, size_t count)
{
        struct atxp1_data *data;
        struct i2c_client *client;
        int vid, cvid;
        unsigned long vcore;
        int err;

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

        err = kstrtoul(buf, 10, &vcore);
        if (err)
                return err;

        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_dbg(dev, "Setting VCore to %d mV (0x%02x)\n", (int)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,
                               struct device_attribute *attr, 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,
                                struct device_attribute *attr, const char *buf,
                                size_t count)
{
        struct atxp1_data *data;
        struct i2c_client *client;
        unsigned long value;
        int err;

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

        err = kstrtoul(buf, 16, &value);
        if (err)
                return err;

        value &= ATXP1_GPIO1MASK;

        if (value != (data->reg.gpio1 & ATXP1_GPIO1MASK)) {
                dev_info(dev, "Writing 0x%x to GPIO1.\n", (unsigned int)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,
                               struct device_attribute *attr, 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,
                                struct device_attribute *attr,
                                const char *buf, size_t count)
{
        struct atxp1_data *data = atxp1_update_device(dev);
        struct i2c_client *client = to_i2c_client(dev);
        unsigned long value;
        int err;

        err = kstrtoul(buf, 16, &value);
        if (err)
                return err;
        value &= 0xff;

        if (value != data->reg.gpio2) {
                dev_info(dev, "Writing 0x%x to GPIO1.\n", (unsigned int)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 struct attribute *atxp1_attributes[] = {
        &dev_attr_gpio1.attr,
        &dev_attr_gpio2.attr,
        &dev_attr_cpu0_vid.attr,
        NULL
};

static const struct attribute_group atxp1_group = {
        .attrs = atxp1_attributes,
};


/* Return 0 if detection is successful, -ENODEV otherwise */
static int atxp1_detect(struct i2c_client *new_client,
                        struct i2c_board_info *info)
{
        struct i2c_adapter *adapter = new_client->adapter;

        u8 temp;

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
                return -ENODEV;

        /* 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)))
                return -ENODEV;

        /*
         * 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)))
                return -ENODEV;

        /* Get VRM */
        temp = vid_which_vrm();

        if ((temp != 90) && (temp != 91)) {
                dev_err(&adapter->dev, "atxp1: Not supporting VRM %d.%d\n",
                                temp / 10, temp % 10);
                return -ENODEV;
        }

        strlcpy(info->type, "atxp1", I2C_NAME_SIZE);

        return 0;
}

static int atxp1_probe(struct i2c_client *new_client,
                       const struct i2c_device_id *id)
{
        struct atxp1_data *data;
        int err;

        data = devm_kzalloc(&new_client->dev, sizeof(struct atxp1_data),
                            GFP_KERNEL);
        if (!data)
                return -ENOMEM;

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

        i2c_set_clientdata(new_client, data);
        data->valid = 0;

        mutex_init(&data->update_lock);

        /* Register sysfs hooks */
        err = sysfs_create_group(&new_client->dev.kobj, &atxp1_group);
        if (err)
                return err;

        data->hwmon_dev = hwmon_device_register(&new_client->dev);
        if (IS_ERR(data->hwmon_dev)) {
                err = PTR_ERR(data->hwmon_dev);
                goto exit_remove_files;
        }

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

        return 0;

exit_remove_files:
        sysfs_remove_group(&new_client->dev.kobj, &atxp1_group);
        return err;
};

static int atxp1_remove(struct i2c_client *client)
{
        struct atxp1_data *data = i2c_get_clientdata(client);

        hwmon_device_unregister(data->hwmon_dev);
        sysfs_remove_group(&client->dev.kobj, &atxp1_group);

        return 0;
};

module_i2c_driver(atxp1_driver);