// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Hardware monitoring driver for FSP 3Y-Power PSUs
 *
 * Copyright (c) 2021 Václav Kubernát, CESNET
 *
 * This driver is mostly reverse engineered with the help of a tool called pmbus_peek written by
 * David Brownell (and later adopted by Jan Kundrát). The device has some sort of a timing issue
 * when switching pages, details are explained in the code. The driver support is limited. It
 * exposes only the values, that have been tested to work correctly. Unsupported values either
 * aren't supported by the devices or their encondings are unknown.
 */

#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include "pmbus.h"

#define YM2151_PAGE_12V_LOG     0x00
#define YM2151_PAGE_12V_REAL    0x00
#define YM2151_PAGE_5VSB_LOG    0x01
#define YM2151_PAGE_5VSB_REAL   0x20
#define YH5151E_PAGE_12V_LOG    0x00
#define YH5151E_PAGE_12V_REAL   0x00
#define YH5151E_PAGE_5V_LOG     0x01
#define YH5151E_PAGE_5V_REAL    0x10
#define YH5151E_PAGE_3V3_LOG    0x02
#define YH5151E_PAGE_3V3_REAL   0x11

enum chips {
        ym2151e,
        yh5151e
};

struct fsp3y_data {
        struct pmbus_driver_info info;
        int chip;
        int page;

        bool vout_linear_11;
};

#define to_fsp3y_data(x) container_of(x, struct fsp3y_data, info)

static int page_log_to_page_real(int page_log, enum chips chip)
{
        switch (chip) {
        case ym2151e:
                switch (page_log) {
                case YM2151_PAGE_12V_LOG:
                        return YM2151_PAGE_12V_REAL;
                case YM2151_PAGE_5VSB_LOG:
                        return YM2151_PAGE_5VSB_REAL;
                }
                return -EINVAL;
        case yh5151e:
                switch (page_log) {
                case YH5151E_PAGE_12V_LOG:
                        return YH5151E_PAGE_12V_REAL;
                case YH5151E_PAGE_5V_LOG:
                        return YH5151E_PAGE_5V_REAL;
                case YH5151E_PAGE_3V3_LOG:
                        return YH5151E_PAGE_3V3_REAL;
                }
                return -EINVAL;
        }

        return -EINVAL;
}

static int set_page(struct i2c_client *client, int page_log)
{
        const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
        struct fsp3y_data *data = to_fsp3y_data(info);
        int rv;
        int page_real;

        if (page_log < 0)
                return 0;

        page_real = page_log_to_page_real(page_log, data->chip);
        if (page_real < 0)
                return page_real;

        if (data->page != page_real) {
                rv = i2c_smbus_write_byte_data(client, PMBUS_PAGE, page_real);
                if (rv < 0)
                        return rv;

                data->page = page_real;

                /*
                 * Testing showed that the device has a timing issue. After
                 * setting a page, it takes a while, before the device actually
                 * gives the correct values from the correct page. 20 ms was
                 * tested to be enough to not give wrong values (15 ms wasn't
                 * enough).
                 */
                usleep_range(20000, 30000);
        }

        return 0;
}

static int fsp3y_read_byte_data(struct i2c_client *client, int page, int reg)
{
        const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
        struct fsp3y_data *data = to_fsp3y_data(info);
        int rv;

        /*
         * Inject an exponent for non-compliant YH5151-E.
         */
        if (data->vout_linear_11 && reg == PMBUS_VOUT_MODE)
                return 0x1A;

        rv = set_page(client, page);
        if (rv < 0)
                return rv;

        return i2c_smbus_read_byte_data(client, reg);
}

static int fsp3y_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 fsp3y_data *data = to_fsp3y_data(info);
        int rv;

        /*
         * This masks commands which weren't tested to work correctly. Some of
         * the masked commands return 0xFFFF. These would probably get tagged as
         * invalid by pmbus_core. Other ones do return values which might be
         * useful (that is, they are not 0xFFFF), but their encoding is unknown,
         * and so they are unsupported.
         */
        switch (reg) {
        case PMBUS_READ_FAN_SPEED_1:
        case PMBUS_READ_IIN:
        case PMBUS_READ_IOUT:
        case PMBUS_READ_PIN:
        case PMBUS_READ_POUT:
        case PMBUS_READ_TEMPERATURE_1:
        case PMBUS_READ_TEMPERATURE_2:
        case PMBUS_READ_TEMPERATURE_3:
        case PMBUS_READ_VIN:
        case PMBUS_READ_VOUT:
        case PMBUS_STATUS_WORD:
                break;
        default:
                return -ENXIO;
        }

        rv = set_page(client, page);
        if (rv < 0)
                return rv;

        rv = i2c_smbus_read_word_data(client, reg);
        if (rv < 0)
                return rv;

        /*
         * Handle YH-5151E non-compliant linear11 vout voltage.
         */
        if (data->vout_linear_11 && reg == PMBUS_READ_VOUT)
                rv = sign_extend32(rv, 10) & 0xffff;

        return rv;
}

static struct pmbus_driver_info fsp3y_info[] = {
        [ym2151e] = {
                .pages = 2,
                .func[YM2151_PAGE_12V_LOG] =
                        PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
                        PMBUS_HAVE_PIN | PMBUS_HAVE_POUT  |
                        PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2 |
                        PMBUS_HAVE_VIN | PMBUS_HAVE_IIN |
                        PMBUS_HAVE_FAN12,
                .func[YM2151_PAGE_5VSB_LOG] =
                        PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT,
                        PMBUS_HAVE_IIN,
                .read_word_data = fsp3y_read_word_data,
                .read_byte_data = fsp3y_read_byte_data,
        },
        [yh5151e] = {
                .pages = 3,
                .func[YH5151E_PAGE_12V_LOG] =
                        PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
                        PMBUS_HAVE_POUT  |
                        PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2 | PMBUS_HAVE_TEMP3,
                .func[YH5151E_PAGE_5V_LOG] =
                        PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
                        PMBUS_HAVE_POUT,
                .func[YH5151E_PAGE_3V3_LOG] =
                        PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
                        PMBUS_HAVE_POUT,
                .read_word_data = fsp3y_read_word_data,
                .read_byte_data = fsp3y_read_byte_data,
        }
};

static int fsp3y_detect(struct i2c_client *client)
{
        int rv;
        u8 buf[I2C_SMBUS_BLOCK_MAX + 1];

        rv = i2c_smbus_read_block_data(client, PMBUS_MFR_MODEL, buf);
        if (rv < 0)
                return rv;

        buf[rv] = '\0';

        if (rv == 8) {
                if (!strcmp(buf, "YM-2151E"))
                        return ym2151e;
                else if (!strcmp(buf, "YH-5151E"))
                        return yh5151e;
        }

        dev_err(&client->dev, "Unsupported model %.*s\n", rv, buf);
        return -ENODEV;
}

static const struct i2c_device_id fsp3y_id[] = {
        {"ym2151e", ym2151e},
        {"yh5151e", yh5151e},
        { }
};

static int fsp3y_probe(struct i2c_client *client)
{
        struct fsp3y_data *data;
        const struct i2c_device_id *id;
        int rv;

        data = devm_kzalloc(&client->dev, sizeof(struct fsp3y_data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->chip = fsp3y_detect(client);
        if (data->chip < 0)
                return data->chip;

        id = i2c_match_id(fsp3y_id, client);
        if (data->chip != id->driver_data)
                dev_warn(&client->dev, "Device mismatch: Configured %s (%d), detected %d\n",
                         id->name, (int)id->driver_data, data->chip);

        rv = i2c_smbus_read_byte_data(client, PMBUS_PAGE);
        if (rv < 0)
                return rv;
        data->page = rv;

        data->info = fsp3y_info[data->chip];

        /*
         * YH-5151E sometimes reports vout in linear11 and sometimes in
         * linear16. This depends on the exact individual piece of hardware. One
         * YH-5151E can use linear16 and another might use linear11 instead.
         *
         * The format can be recognized by reading VOUT_MODE - if it doesn't
         * report a valid exponent, then vout uses linear11. Otherwise, the
         * device is compliant and uses linear16.
         */
        data->vout_linear_11 = false;
        if (data->chip == yh5151e) {
                rv = i2c_smbus_read_byte_data(client, PMBUS_VOUT_MODE);
                if (rv < 0)
                        return rv;

                if (rv == 0xFF)
                        data->vout_linear_11 = true;
        }

        return pmbus_do_probe(client, &data->info);
}

MODULE_DEVICE_TABLE(i2c, fsp3y_id);

static struct i2c_driver fsp3y_driver = {
        .driver = {
                   .name = "fsp3y",
                   },
        .probe_new = fsp3y_probe,
        .id_table = fsp3y_id
};

module_i2c_driver(fsp3y_driver);

MODULE_AUTHOR("Václav Kubernát");
MODULE_DESCRIPTION("PMBus driver for FSP/3Y-Power power supplies");
MODULE_LICENSE("GPL");
MODULE_IMPORT_NS(PMBUS);