/*
 * 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.
 *
 * The ATXP1 can reside on I2C addresses 0x37 or 0x4e. The chip is
 * not auto-detected by the driver and must be instantiated explicitly.
 * See Documentation/i2c/instantiating-devices for more information.
 */

#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

struct atxp1_data {
        struct i2c_client *client;
        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 atxp1_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->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 = atxp1_update_device(dev);
        struct i2c_client *client = data->client;
        int vid, cvid;
        unsigned long vcore;
        int err;

        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 vid;
        }

        /*
         * 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 = atxp1_update_device(dev);
        struct i2c_client *client = data->client;
        unsigned long value;
        int err;

        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 = data->client;
        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_attrs[] = {
        &dev_attr_gpio1.attr,
        &dev_attr_gpio2.attr,
        &dev_attr_cpu0_vid.attr,
        NULL
};
ATTRIBUTE_GROUPS(atxp1);

static int atxp1_probe(struct i2c_client *client,
                       const struct i2c_device_id *id)
{
        struct device *dev = &client->dev;
        struct atxp1_data *data;
        struct device *hwmon_dev;

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

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

        data->client = client;
        mutex_init(&data->update_lock);

        hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
                                                           data,
                                                           atxp1_groups);
        if (IS_ERR(hwmon_dev))
                return PTR_ERR(hwmon_dev);

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

        return 0;
};

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,
        .id_table       = atxp1_id,
};

module_i2c_driver(atxp1_driver);