// SPDX-License-Identifier: GPL-2.0
/*
 * The Gateworks System Controller (GSC) is a multi-function
 * device designed for use in Gateworks Single Board Computers.
 * The control interface is I2C, with an interrupt. The device supports
 * system functions such as push-button monitoring, multiple ADC's for
 * voltage and temperature monitoring, fan controller and watchdog monitor.
 *
 * Copyright (C) 2020 Gateworks Corporation
 */

#include <linux/device.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/mfd/gsc.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>

#include <linux/unaligned.h>

/*
 * The GSC suffers from an errata where occasionally during
 * ADC cycles the chip can NAK I2C transactions. To ensure we have reliable
 * register access we place retries around register access.
 */
#define I2C_RETRIES     3

int gsc_write(void *context, unsigned int reg, unsigned int val)
{
        struct i2c_client *client = context;
        int retry, ret;

        for (retry = 0; retry < I2C_RETRIES; retry++) {
                ret = i2c_smbus_write_byte_data(client, reg, val);
                /*
                 * -EAGAIN returned when the i2c host controller is busy
                 * -EIO returned when i2c device is busy
                 */
                if (ret != -EAGAIN && ret != -EIO)
                        break;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(gsc_write);

int gsc_read(void *context, unsigned int reg, unsigned int *val)
{
        struct i2c_client *client = context;
        int retry, ret;

        for (retry = 0; retry < I2C_RETRIES; retry++) {
                ret = i2c_smbus_read_byte_data(client, reg);
                /*
                 * -EAGAIN returned when the i2c host controller is busy
                 * -EIO returned when i2c device is busy
                 */
                if (ret != -EAGAIN && ret != -EIO)
                        break;
        }
        *val = ret & 0xff;

        return 0;
}
EXPORT_SYMBOL_GPL(gsc_read);

/*
 * gsc_powerdown - API to use GSC to power down board for a specific time
 *
 * secs - number of seconds to remain powered off
 */
static int gsc_powerdown(struct gsc_dev *gsc, unsigned long secs)
{
        int ret;
        unsigned char regs[4];

        dev_info(&gsc->i2c->dev, "GSC powerdown for %ld seconds\n",
                 secs);

        put_unaligned_le32(secs, regs);
        ret = regmap_bulk_write(gsc->regmap, GSC_TIME_ADD, regs, 4);
        if (ret)
                return ret;

        ret = regmap_update_bits(gsc->regmap, GSC_CTRL_1,
                                 BIT(GSC_CTRL_1_SLEEP_ADD),
                                 BIT(GSC_CTRL_1_SLEEP_ADD));
        if (ret)
                return ret;

        ret = regmap_update_bits(gsc->regmap, GSC_CTRL_1,
                                 BIT(GSC_CTRL_1_SLEEP_ACTIVATE) |
                                 BIT(GSC_CTRL_1_SLEEP_ENABLE),
                                 BIT(GSC_CTRL_1_SLEEP_ACTIVATE) |
                                 BIT(GSC_CTRL_1_SLEEP_ENABLE));


        return ret;
}

static ssize_t gsc_show(struct device *dev, struct device_attribute *attr,
                        char *buf)
{
        struct gsc_dev *gsc = dev_get_drvdata(dev);
        const char *name = attr->attr.name;
        int rz = 0;

        if (strcasecmp(name, "fw_version") == 0)
                rz = sprintf(buf, "%d\n", gsc->fwver);
        else if (strcasecmp(name, "fw_crc") == 0)
                rz = sprintf(buf, "0x%04x\n", gsc->fwcrc);
        else
                dev_err(dev, "invalid command: '%s'\n", name);

        return rz;
}

static ssize_t gsc_store(struct device *dev, struct device_attribute *attr,
                         const char *buf, size_t count)
{
        struct gsc_dev *gsc = dev_get_drvdata(dev);
        const char *name = attr->attr.name;
        long value;

        if (strcasecmp(name, "powerdown") == 0) {
                if (kstrtol(buf, 0, &value) == 0)
                        gsc_powerdown(gsc, value);
        } else {
                dev_err(dev, "invalid command: '%s\n", name);
        }

        return count;
}

static struct device_attribute attr_fwver =
        __ATTR(fw_version, 0440, gsc_show, NULL);
static struct device_attribute attr_fwcrc =
        __ATTR(fw_crc, 0440, gsc_show, NULL);
static struct device_attribute attr_pwrdown =
        __ATTR(powerdown, 0220, NULL, gsc_store);

static struct attribute *gsc_attrs[] = {
        &attr_fwver.attr,
        &attr_fwcrc.attr,
        &attr_pwrdown.attr,
        NULL,
};

static struct attribute_group attr_group = {
        .attrs = gsc_attrs,
};

static const struct of_device_id gsc_of_match[] = {
        { .compatible = "gw,gsc", },
        { }
};
MODULE_DEVICE_TABLE(of, gsc_of_match);

static const struct regmap_bus gsc_regmap_bus = {
        .reg_read = gsc_read,
        .reg_write = gsc_write,
};

static const struct regmap_config gsc_regmap_config = {
        .reg_bits = 8,
        .val_bits = 8,
        .cache_type = REGCACHE_NONE,
        .max_register = GSC_WP,
};

static const struct regmap_irq gsc_irqs[] = {
        REGMAP_IRQ_REG(GSC_IRQ_PB, 0, BIT(GSC_IRQ_PB)),
        REGMAP_IRQ_REG(GSC_IRQ_KEY_ERASED, 0, BIT(GSC_IRQ_KEY_ERASED)),
        REGMAP_IRQ_REG(GSC_IRQ_EEPROM_WP, 0, BIT(GSC_IRQ_EEPROM_WP)),
        REGMAP_IRQ_REG(GSC_IRQ_RESV, 0, BIT(GSC_IRQ_RESV)),
        REGMAP_IRQ_REG(GSC_IRQ_GPIO, 0, BIT(GSC_IRQ_GPIO)),
        REGMAP_IRQ_REG(GSC_IRQ_TAMPER, 0, BIT(GSC_IRQ_TAMPER)),
        REGMAP_IRQ_REG(GSC_IRQ_WDT_TIMEOUT, 0, BIT(GSC_IRQ_WDT_TIMEOUT)),
        REGMAP_IRQ_REG(GSC_IRQ_SWITCH_HOLD, 0, BIT(GSC_IRQ_SWITCH_HOLD)),
};

static const struct regmap_irq_chip gsc_irq_chip = {
        .name = "gateworks-gsc",
        .irqs = gsc_irqs,
        .num_irqs = ARRAY_SIZE(gsc_irqs),
        .num_regs = 1,
        .status_base = GSC_IRQ_STATUS,
        .unmask_base = GSC_IRQ_ENABLE,
        .ack_base = GSC_IRQ_STATUS,
        .ack_invert = true,
};

static int gsc_probe(struct i2c_client *client)
{
        struct device *dev = &client->dev;
        struct gsc_dev *gsc;
        struct regmap_irq_chip_data *irq_data;
        int ret;
        unsigned int reg;

        gsc = devm_kzalloc(dev, sizeof(*gsc), GFP_KERNEL);
        if (!gsc)
                return -ENOMEM;

        gsc->dev = &client->dev;
        gsc->i2c = client;
        i2c_set_clientdata(client, gsc);

        gsc->regmap = devm_regmap_init(dev, &gsc_regmap_bus, client,
                                       &gsc_regmap_config);
        if (IS_ERR(gsc->regmap))
                return PTR_ERR(gsc->regmap);

        if (regmap_read(gsc->regmap, GSC_FW_VER, &reg))
                return -EIO;
        gsc->fwver = reg;

        regmap_read(gsc->regmap, GSC_FW_CRC, &reg);
        gsc->fwcrc = reg;
        regmap_read(gsc->regmap, GSC_FW_CRC + 1, &reg);
        gsc->fwcrc |= reg << 8;

        gsc->i2c_hwmon = devm_i2c_new_dummy_device(dev, client->adapter,
                                                   GSC_HWMON);
        if (IS_ERR(gsc->i2c_hwmon)) {
                dev_err(dev, "Failed to allocate I2C device for HWMON\n");
                return PTR_ERR(gsc->i2c_hwmon);
        }

        ret = devm_regmap_add_irq_chip(dev, gsc->regmap, client->irq,
                                       IRQF_ONESHOT | IRQF_SHARED |
                                       IRQF_TRIGGER_LOW, 0,
                                       &gsc_irq_chip, &irq_data);
        if (ret)
                return ret;

        dev_info(dev, "Gateworks System Controller v%d: fw 0x%04x\n",
                 gsc->fwver, gsc->fwcrc);

        ret = sysfs_create_group(&dev->kobj, &attr_group);
        if (ret)
                dev_err(dev, "failed to create sysfs attrs\n");

        ret = devm_of_platform_populate(dev);
        if (ret) {
                sysfs_remove_group(&dev->kobj, &attr_group);
                return ret;
        }

        return 0;
}

static void gsc_remove(struct i2c_client *client)
{
        sysfs_remove_group(&client->dev.kobj, &attr_group);
}

static struct i2c_driver gsc_driver = {
        .driver = {
                .name   = "gateworks-gsc",
                .of_match_table = gsc_of_match,
        },
        .probe          = gsc_probe,
        .remove         = gsc_remove,
};
module_i2c_driver(gsc_driver);

MODULE_AUTHOR("Tim Harvey <tharvey@gateworks.com>");
MODULE_DESCRIPTION("I2C Core interface for GSC");
MODULE_LICENSE("GPL v2");