// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Hardware monitoring driver for Maxim MAX15301
 *
 * Copyright (c) 2021 Flextronics International Sweden AB
 *
 * Even though the specification does not specifically mention it,
 * extensive empirical testing has revealed that auto-detection of
 * limit-registers will fail in a random fashion unless the delay
 * parameter is set to above about 80us. The default delay is set
 * to 100us to include some safety margin.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/ktime.h>
#include <linux/delay.h>
#include <linux/pmbus.h>
#include "pmbus.h"

static const struct i2c_device_id max15301_id[] = {
        {"bmr461", 0},
        {"max15301", 0},
        {}
};
MODULE_DEVICE_TABLE(i2c, max15301_id);

struct max15301_data {
        int id;
        ktime_t access;         /* Chip access time */
        int delay;              /* Delay between chip accesses in us */
        struct pmbus_driver_info info;
};

#define to_max15301_data(x)  container_of(x, struct max15301_data, info)

#define MAX15301_WAIT_TIME              100     /* us   */

static ushort delay = MAX15301_WAIT_TIME;
module_param(delay, ushort, 0644);
MODULE_PARM_DESC(delay, "Delay between chip accesses in us");

static struct max15301_data max15301_data = {
        .info = {
                .pages = 1,
                .func[0] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT
                        | PMBUS_HAVE_VIN | PMBUS_HAVE_STATUS_INPUT
                        | PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2
                        | PMBUS_HAVE_STATUS_TEMP
                        | PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT,
        }
};

/* This chip needs a delay between accesses */
static inline void max15301_wait(const struct max15301_data *data)
{
        if (data->delay) {
                s64 delta = ktime_us_delta(ktime_get(), data->access);

                if (delta < data->delay)
                        udelay(data->delay - delta);
        }
}

static int max15301_read_word_data(struct i2c_client *client, int page,
                                   int phase, int reg)
{
        const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
        struct max15301_data *data = to_max15301_data(info);
        int ret;

        if (page > 0)
                return -ENXIO;

        if (reg >= PMBUS_VIRT_BASE)
                return -ENXIO;

        max15301_wait(data);
        ret = pmbus_read_word_data(client, page, phase, reg);
        data->access = ktime_get();

        return ret;
}

static int max15301_read_byte_data(struct i2c_client *client, int page, int reg)
{
        const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
        struct max15301_data *data = to_max15301_data(info);
        int ret;

        if (page > 0)
                return -ENXIO;

        max15301_wait(data);
        ret = pmbus_read_byte_data(client, page, reg);
        data->access = ktime_get();

        return ret;
}

static int max15301_write_word_data(struct i2c_client *client, int page, int reg,
                                    u16 word)
{
        const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
        struct max15301_data *data = to_max15301_data(info);
        int ret;

        if (page > 0)
                return -ENXIO;

        if (reg >= PMBUS_VIRT_BASE)
                return -ENXIO;

        max15301_wait(data);
        ret = pmbus_write_word_data(client, page, reg, word);
        data->access = ktime_get();

        return ret;
}

static int max15301_write_byte(struct i2c_client *client, int page, u8 value)
{
        const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
        struct max15301_data *data = to_max15301_data(info);
        int ret;

        if (page > 0)
                return -ENXIO;

        max15301_wait(data);
        ret = pmbus_write_byte(client, page, value);
        data->access = ktime_get();

        return ret;
}

static int max15301_probe(struct i2c_client *client)
{
        int status;
        u8 device_id[I2C_SMBUS_BLOCK_MAX + 1];
        const struct i2c_device_id *mid;
        struct pmbus_driver_info *info = &max15301_data.info;

        if (!i2c_check_functionality(client->adapter,
                                     I2C_FUNC_SMBUS_READ_BYTE_DATA
                                     | I2C_FUNC_SMBUS_BLOCK_DATA))
                return -ENODEV;

        status = i2c_smbus_read_block_data(client, PMBUS_IC_DEVICE_ID, device_id);
        if (status < 0) {
                dev_err(&client->dev, "Failed to read Device Id\n");
                return status;
        }
        for (mid = max15301_id; mid->name[0]; mid++) {
                if (!strncasecmp(mid->name, device_id, strlen(mid->name)))
                        break;
        }
        if (!mid->name[0]) {
                dev_err(&client->dev, "Unsupported device\n");
                return -ENODEV;
        }

        max15301_data.delay = delay;

        info->read_byte_data = max15301_read_byte_data;
        info->read_word_data = max15301_read_word_data;
        info->write_byte = max15301_write_byte;
        info->write_word_data = max15301_write_word_data;

        return pmbus_do_probe(client, info);
}

static struct i2c_driver max15301_driver = {
        .driver = {
                   .name = "max15301",
                   },
        .probe_new = max15301_probe,
        .id_table = max15301_id,
};

module_i2c_driver(max15301_driver);

MODULE_AUTHOR("Erik Rosen <erik.rosen@metormote.com>");
MODULE_DESCRIPTION("PMBus driver for Maxim MAX15301");
MODULE_LICENSE("GPL");
MODULE_IMPORT_NS(PMBUS);