// SPDX-License-Identifier: GPL-2.0-only
/*
 * ti_fpc202.c - FPC202 Dual Port Controller driver
 *
 * Copyright (C) 2024 Bootlin
 *
 */

#include <linux/cleanup.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/i2c-atr.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include <linux/module.h>

#define FPC202_NUM_PORTS 2
#define FPC202_ALIASES_PER_PORT 2

/*
 * GPIO: port mapping
 *
 * 0: P0_S0_IN_A
 * 1: P0_S1_IN_A
 * 2: P1_S0_IN_A
 * 3: P1_S1_IN_A
 * 4: P0_S0_IN_B
 * ...
 * 8: P0_S0_IN_C
 * ...
 * 12: P0_S0_OUT_A
 * ...
 * 16: P0_S0_OUT_B
 * ...
 * 19: P1_S1_OUT_B
 *
 */

#define FPC202_GPIO_COUNT 20
#define FPC202_GPIO_P0_S0_IN_B  4
#define FPC202_GPIO_P0_S0_OUT_A 12

#define FPC202_REG_IN_A_INT    0x6
#define FPC202_REG_IN_C_IN_B   0x7
#define FPC202_REG_OUT_A_OUT_B 0x8

#define FPC202_REG_OUT_A_OUT_B_VAL 0xa

#define FPC202_REG_MOD_DEV(port, dev) (0xb4 + ((port) * 4) + (dev))
#define FPC202_REG_AUX_DEV(port, dev) (0xb6 + ((port) * 4) + (dev))

/*
 * The FPC202 doesn't support turning off address translation on a single port.
 * So just set an invalid I2C address as the translation target when no client
 * address is attached.
 */
#define FPC202_REG_DEV_INVALID 0

/* Even aliases are assigned to device 0 and odd aliases to device 1 */
#define fpc202_dev_num_from_alias(alias) ((alias) % 2)

struct fpc202_priv {
        struct i2c_client *client;
        struct i2c_atr *atr;
        struct gpio_desc *en_gpio;
        struct gpio_chip gpio;

        /* Lock REG_MOD/AUX_DEV and addr_caches during attach/detach */
        struct mutex reg_dev_lock;

        /* Cached device addresses for both ports and their devices */
        u8 addr_caches[2][2];

        /* Keep track of which ports were probed */
        DECLARE_BITMAP(probed_ports, FPC202_NUM_PORTS);
};

static void fpc202_fill_alias_table(struct i2c_client *client, u16 *aliases, int port_id)
{
        u16 first_alias;
        int i;

        /*
         * There is a predefined list of aliases for each FPC202 I2C
         * self-address.  This allows daisy-chained FPC202 units to
         * automatically take on different sets of aliases.
         * Each port of an FPC202 unit is assigned two aliases from this list.
         */
        first_alias = 0x10 + 4 * port_id + 8 * ((u16)client->addr - 2);

        for (i = 0; i < FPC202_ALIASES_PER_PORT; i++)
                aliases[i] = first_alias + i;
}

static int fpc202_gpio_get_dir(int offset)
{
        return offset < FPC202_GPIO_P0_S0_OUT_A ? GPIO_LINE_DIRECTION_IN : GPIO_LINE_DIRECTION_OUT;
}

static int fpc202_read(struct fpc202_priv *priv, u8 reg)
{
        int val;

        val = i2c_smbus_read_byte_data(priv->client, reg);
        return val;
}

static int fpc202_write(struct fpc202_priv *priv, u8 reg, u8 value)
{
        return i2c_smbus_write_byte_data(priv->client, reg, value);
}

static void fpc202_set_enable(struct fpc202_priv *priv, int enable)
{
        if (!priv->en_gpio)
                return;

        gpiod_set_value(priv->en_gpio, enable);
}

static int fpc202_gpio_set(struct gpio_chip *chip, unsigned int offset,
                           int value)
{
        struct fpc202_priv *priv = gpiochip_get_data(chip);
        int ret;
        u8 val;

        ret = fpc202_read(priv, FPC202_REG_OUT_A_OUT_B_VAL);
        if (ret < 0) {
                dev_err(&priv->client->dev, "Failed to set GPIO %d value! err %d\n", offset, ret);
                return ret;
        }

        val = (u8)ret;

        if (value)
                val |= BIT(offset - FPC202_GPIO_P0_S0_OUT_A);
        else
                val &= ~BIT(offset - FPC202_GPIO_P0_S0_OUT_A);

        return fpc202_write(priv, FPC202_REG_OUT_A_OUT_B_VAL, val);
}

static int fpc202_gpio_get(struct gpio_chip *chip, unsigned int offset)
{
        struct fpc202_priv *priv = gpiochip_get_data(chip);
        u8 reg, bit;
        int ret;

        if (offset < FPC202_GPIO_P0_S0_IN_B) {
                reg = FPC202_REG_IN_A_INT;
                bit = BIT(4 + offset);
        } else if (offset < FPC202_GPIO_P0_S0_OUT_A) {
                reg = FPC202_REG_IN_C_IN_B;
                bit = BIT(offset - FPC202_GPIO_P0_S0_IN_B);
        } else {
                reg = FPC202_REG_OUT_A_OUT_B_VAL;
                bit = BIT(offset - FPC202_GPIO_P0_S0_OUT_A);
        }

        ret = fpc202_read(priv, reg);
        if (ret < 0)
                return ret;

        return !!(((u8)ret) & bit);
}

static int fpc202_gpio_direction_input(struct gpio_chip *chip, unsigned int offset)
{
        if (fpc202_gpio_get_dir(offset) == GPIO_LINE_DIRECTION_OUT)
                return -EINVAL;

        return 0;
}

static int fpc202_gpio_direction_output(struct gpio_chip *chip, unsigned int offset,
                                        int value)
{
        struct fpc202_priv *priv = gpiochip_get_data(chip);
        int ret;
        u8 val;

        if (fpc202_gpio_get_dir(offset) == GPIO_LINE_DIRECTION_IN)
                return -EINVAL;

        fpc202_gpio_set(chip, offset, value);

        ret = fpc202_read(priv, FPC202_REG_OUT_A_OUT_B);
        if (ret < 0)
                return ret;

        val = (u8)ret | BIT(offset - FPC202_GPIO_P0_S0_OUT_A);

        return fpc202_write(priv, FPC202_REG_OUT_A_OUT_B, val);
}

/*
 * Set the translation table entry associated with a port and device number.
 *
 * Each downstream port of the FPC202 has two fixed aliases corresponding to
 * device numbers 0 and 1. If one of these aliases is found in an incoming I2C
 * transfer, it will be translated to the address given by the corresponding
 * translation table entry.
 */
static int fpc202_write_dev_addr(struct fpc202_priv *priv, u32 port_id, int dev_num, u16 addr)
{
        int ret, reg_mod, reg_aux;
        u8 val;

        guard(mutex)(&priv->reg_dev_lock);

        reg_mod = FPC202_REG_MOD_DEV(port_id, dev_num);
        reg_aux = FPC202_REG_AUX_DEV(port_id, dev_num);
        val = addr & 0x7f;

        ret = fpc202_write(priv, reg_mod, val);
        if (ret)
                return ret;

        /*
         * The FPC202 datasheet is unclear about the role of the AUX registers.
         * Empirically, writing to them as well seems to be necessary for
         * address translation to function properly.
         */
        ret = fpc202_write(priv, reg_aux, val);

        priv->addr_caches[port_id][dev_num] = val;

        return ret;
}

static int fpc202_attach_addr(struct i2c_atr *atr, u32 chan_id,
                              u16 addr, u16 alias)
{
        struct fpc202_priv *priv = i2c_atr_get_driver_data(atr);

        dev_dbg(&priv->client->dev, "attaching address 0x%02x to alias 0x%02x\n", addr, alias);

        return fpc202_write_dev_addr(priv, chan_id, fpc202_dev_num_from_alias(alias), addr);
}

static void fpc202_detach_addr(struct i2c_atr *atr, u32 chan_id,
                               u16 addr)
{
        struct fpc202_priv *priv = i2c_atr_get_driver_data(atr);
        int dev_num, reg_mod, val;

        for (dev_num = 0; dev_num < 2; dev_num++) {
                reg_mod = FPC202_REG_MOD_DEV(chan_id, dev_num);

                mutex_lock(&priv->reg_dev_lock);

                val = priv->addr_caches[chan_id][dev_num];

                mutex_unlock(&priv->reg_dev_lock);

                if (val < 0) {
                        dev_err(&priv->client->dev, "failed to read register 0x%x while detaching address 0x%02x\n",
                                reg_mod, addr);
                        return;
                }

                if (val == (addr & 0x7f)) {
                        fpc202_write_dev_addr(priv, chan_id, dev_num, FPC202_REG_DEV_INVALID);
                        return;
                }
        }
}

static const struct i2c_atr_ops fpc202_atr_ops = {
        .attach_addr = fpc202_attach_addr,
        .detach_addr = fpc202_detach_addr,
};

static int fpc202_probe_port(struct fpc202_priv *priv, struct device_node *i2c_handle, int port_id)
{
        u16 aliases[FPC202_ALIASES_PER_PORT] = { };
        struct device *dev = &priv->client->dev;
        struct i2c_atr_adap_desc desc = { };
        int ret = 0;

        desc.chan_id = port_id;
        desc.parent = dev;
        desc.bus_handle = of_fwnode_handle(i2c_handle);
        desc.num_aliases = FPC202_ALIASES_PER_PORT;

        fpc202_fill_alias_table(priv->client, aliases, port_id);
        desc.aliases = aliases;

        ret = i2c_atr_add_adapter(priv->atr, &desc);
        if (ret)
                return ret;

        set_bit(port_id, priv->probed_ports);

        ret = fpc202_write_dev_addr(priv, port_id, 0, FPC202_REG_DEV_INVALID);
        if (ret)
                return ret;

        return fpc202_write_dev_addr(priv, port_id, 1, FPC202_REG_DEV_INVALID);
}

static void fpc202_remove_port(struct fpc202_priv *priv, int port_id)
{
        i2c_atr_del_adapter(priv->atr, port_id);
        clear_bit(port_id, priv->probed_ports);
}

static int fpc202_probe(struct i2c_client *client)
{
        struct device *dev = &client->dev;
        struct fpc202_priv *priv;
        int ret, port_id;

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

        mutex_init(&priv->reg_dev_lock);

        priv->client = client;
        i2c_set_clientdata(client, priv);

        priv->en_gpio = devm_gpiod_get_optional(dev, "enable", GPIOD_OUT_HIGH);
        if (IS_ERR(priv->en_gpio)) {
                ret = PTR_ERR(priv->en_gpio);
                dev_err(dev, "failed to fetch enable GPIO! err %d\n", ret);
                goto destroy_mutex;
        }

        priv->gpio.label = "gpio-fpc202";
        priv->gpio.base = -1;
        priv->gpio.direction_input = fpc202_gpio_direction_input;
        priv->gpio.direction_output = fpc202_gpio_direction_output;
        priv->gpio.set = fpc202_gpio_set;
        priv->gpio.get = fpc202_gpio_get;
        priv->gpio.ngpio = FPC202_GPIO_COUNT;
        priv->gpio.parent = dev;
        priv->gpio.owner = THIS_MODULE;

        ret = gpiochip_add_data(&priv->gpio, priv);
        if (ret) {
                priv->gpio.parent = NULL;
                dev_err(dev, "failed to add gpiochip err %d\n", ret);
                goto disable_gpio;
        }

        priv->atr = i2c_atr_new(client->adapter, dev, &fpc202_atr_ops, 2, 0);
        if (IS_ERR(priv->atr)) {
                ret = PTR_ERR(priv->atr);
                dev_err(dev, "failed to create i2c atr err %d\n", ret);
                goto disable_gpio;
        }

        i2c_atr_set_driver_data(priv->atr, priv);

        bitmap_zero(priv->probed_ports, FPC202_NUM_PORTS);

        for_each_child_of_node_scoped(dev->of_node, i2c_handle) {
                ret = of_property_read_u32(i2c_handle, "reg", &port_id);
                if (ret) {
                        if (ret == -EINVAL)
                                continue;

                        dev_err(dev, "failed to read 'reg' property of child node, err %d\n", ret);
                        goto unregister_chans;
                }

                if (port_id > FPC202_NUM_PORTS) {
                        dev_err(dev, "port ID %d is out of range!\n", port_id);
                        ret = -EINVAL;
                        goto unregister_chans;
                }

                ret = fpc202_probe_port(priv, i2c_handle, port_id);
                if (ret) {
                        dev_err(dev, "Failed to probe port %d, err %d\n", port_id, ret);
                        goto unregister_chans;
                }
        }

        goto out;

unregister_chans:
        for_each_set_bit(port_id, priv->probed_ports, FPC202_NUM_PORTS)
                fpc202_remove_port(priv, port_id);

        i2c_atr_delete(priv->atr);
disable_gpio:
        fpc202_set_enable(priv, 0);
        gpiochip_remove(&priv->gpio);
destroy_mutex:
        mutex_destroy(&priv->reg_dev_lock);
out:
        return ret;
}

static void fpc202_remove(struct i2c_client *client)
{
        struct fpc202_priv *priv = i2c_get_clientdata(client);
        int port_id;

        for_each_set_bit(port_id, priv->probed_ports, FPC202_NUM_PORTS)
                fpc202_remove_port(priv, port_id);

        mutex_destroy(&priv->reg_dev_lock);

        i2c_atr_delete(priv->atr);

        fpc202_set_enable(priv, 0);
        gpiochip_remove(&priv->gpio);
}

static const struct of_device_id fpc202_of_match[] = {
        { .compatible = "ti,fpc202" },
        {}
};
MODULE_DEVICE_TABLE(of, fpc202_of_match);

static struct i2c_driver fpc202_driver = {
        .driver = {
                .name = "fpc202",
                .of_match_table = fpc202_of_match,
        },
        .probe = fpc202_probe,
        .remove = fpc202_remove,
};

module_i2c_driver(fpc202_driver);

MODULE_AUTHOR("Romain Gantois <romain.gantois@bootlin.com>");
MODULE_DESCRIPTION("TI FPC202 Dual Port Controller driver");
MODULE_LICENSE("GPL");
MODULE_IMPORT_NS("I2C_ATR");