// SPDX-License-Identifier: GPL-2.0-only
/*
 * Awinic AW9523B i2c pin controller driver
 * Copyright (c) 2020, AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
 */

#include <linux/bitfield.h>
#include <linux/errno.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/property.h>
#include <linux/regmap.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>

#include <linux/pinctrl/pinconf-generic.h>
#include <linux/pinctrl/pinconf.h>
#include <linux/pinctrl/pinctrl.h>
#include <linux/pinctrl/pinmux.h>

#define AW9523_MAX_FUNCS                2
#define AW9523_NUM_PORTS                2
#define AW9523_PINS_PER_PORT            8

/*
 * HW needs at least 20uS for reset and at least 1-2uS to recover from
 * reset, but we have to account for eventual board quirks, if any:
 * for this reason, keep reset asserted for 50uS and wait for 20uS
 * to recover from the reset.
 */
#define AW9523_HW_RESET_US              50
#define AW9523_HW_RESET_RECOVERY_US     20

/* Port 0: P0_0...P0_7 - Port 1: P1_0...P1_7 */
#define AW9523_PIN_TO_PORT(pin)         (pin >> 3)
#define AW9523_REG_IN_STATE(pin)        (0x00 + AW9523_PIN_TO_PORT(pin))
#define AW9523_REG_OUT_STATE(pin)       (0x02 + AW9523_PIN_TO_PORT(pin))
#define AW9523_REG_CONF_STATE(pin)      (0x04 + AW9523_PIN_TO_PORT(pin))
#define AW9523_REG_INTR_DIS(pin)        (0x06 + AW9523_PIN_TO_PORT(pin))
#define AW9523_REG_CHIPID               0x10
#define AW9523_VAL_EXPECTED_CHIPID      0x23

#define AW9523_REG_GCR                  0x11
#define AW9523_GCR_ISEL_MASK            GENMASK(0, 1)
#define AW9523_GCR_GPOMD_MASK           BIT(4)

#define AW9523_REG_PORT_MODE(pin)       (0x12 + AW9523_PIN_TO_PORT(pin))
#define AW9523_REG_SOFT_RESET           0x7f
#define AW9523_VAL_RESET                0x00

/*
 * struct aw9523_irq - Interrupt controller structure
 * @lock: mutex locking for the irq bus
 * @cached_gpio: stores the previous gpio status for bit comparison
 */
struct aw9523_irq {
        struct mutex lock;
        u16 cached_gpio;
};

/*
 * struct aw9523 - Main driver structure
 * @dev: device handle
 * @regmap: regmap handle for current device
 * @i2c_lock: Mutex lock for i2c operations
 * @reset_gpio: Hardware reset (RSTN) signal GPIO
 * @vio_vreg: VCC regulator (Optional)
 * @pctl: pinctrl handle for current device
 * @gpio: structure holding gpiochip params
 * @irq: Interrupt controller structure
 */
struct aw9523 {
        struct device *dev;
        struct regmap *regmap;
        struct mutex i2c_lock;
        struct gpio_desc *reset_gpio;
        int vio_vreg;
        struct pinctrl_dev *pctl;
        struct gpio_chip gpio;
        struct aw9523_irq *irq;
};

static const struct pinctrl_pin_desc aw9523_pins[] = {
        /* Port 0 */
        PINCTRL_PIN(0, "gpio0"),
        PINCTRL_PIN(1, "gpio1"),
        PINCTRL_PIN(2, "gpio2"),
        PINCTRL_PIN(3, "gpio3"),
        PINCTRL_PIN(4, "gpio4"),
        PINCTRL_PIN(5, "gpio5"),
        PINCTRL_PIN(6, "gpio6"),
        PINCTRL_PIN(7, "gpio7"),

        /* Port 1 */
        PINCTRL_PIN(8, "gpio8"),
        PINCTRL_PIN(9, "gpio9"),
        PINCTRL_PIN(10, "gpio10"),
        PINCTRL_PIN(11, "gpio11"),
        PINCTRL_PIN(12, "gpio12"),
        PINCTRL_PIN(13, "gpio13"),
        PINCTRL_PIN(14, "gpio14"),
        PINCTRL_PIN(15, "gpio15"),
};

static int aw9523_pinctrl_get_groups_count(struct pinctrl_dev *pctldev)
{
        return ARRAY_SIZE(aw9523_pins);
}

static const char *aw9523_pinctrl_get_group_name(struct pinctrl_dev *pctldev,
                                                 unsigned int selector)
{
        return aw9523_pins[selector].name;
}

static int aw9523_pinctrl_get_group_pins(struct pinctrl_dev *pctldev,
                                         unsigned int selector,
                                         const unsigned int **pins,
                                         unsigned int *num_pins)
{
        *pins = &aw9523_pins[selector].number;
        *num_pins = 1;
        return 0;
}

static const struct pinctrl_ops aw9523_pinctrl_ops = {
        .get_groups_count = aw9523_pinctrl_get_groups_count,
        .get_group_pins = aw9523_pinctrl_get_group_pins,
        .get_group_name = aw9523_pinctrl_get_group_name,
        .dt_node_to_map = pinconf_generic_dt_node_to_map_pin,
        .dt_free_map = pinconf_generic_dt_free_map,
};

static const char * const gpio_pwm_groups[] = {
        "gpio0", "gpio1", "gpio2", "gpio3",             /* 0-3 */
        "gpio4", "gpio5", "gpio6", "gpio7",             /* 4-7 */
        "gpio8", "gpio9", "gpio10", "gpio11",           /* 8-11 */
        "gpio12", "gpio13", "gpio14", "gpio15",         /* 11-15 */
};

/* Warning: Do NOT reorder this array */
static const struct pinfunction aw9523_pmx[] = {
        PINCTRL_PINFUNCTION("pwm", gpio_pwm_groups, ARRAY_SIZE(gpio_pwm_groups)),
        PINCTRL_PINFUNCTION("gpio", gpio_pwm_groups, ARRAY_SIZE(gpio_pwm_groups)),
};

static int aw9523_pmx_get_funcs_count(struct pinctrl_dev *pctl)
{
        return ARRAY_SIZE(aw9523_pmx);
}

static const char *aw9523_pmx_get_fname(struct pinctrl_dev *pctl,
                                        unsigned int sel)
{
        return aw9523_pmx[sel].name;
}

static int aw9523_pmx_get_groups(struct pinctrl_dev *pctl, unsigned int sel,
                                 const char * const **groups,
                                 unsigned int * const ngroups)
{
        *groups = aw9523_pmx[sel].groups;
        *ngroups = aw9523_pmx[sel].ngroups;
        return 0;
}

static int aw9523_pmx_set_mux(struct pinctrl_dev *pctl, unsigned int fsel,
                              unsigned int grp)
{
        struct aw9523 *awi = pinctrl_dev_get_drvdata(pctl);
        int ret, pin = aw9523_pins[grp].number % AW9523_PINS_PER_PORT;

        if (fsel >= ARRAY_SIZE(aw9523_pmx))
                return -EINVAL;

        /*
         * This maps directly to the aw9523_pmx array: programming a
         * high bit means "gpio" and a low bit means "pwm".
         */
        mutex_lock(&awi->i2c_lock);
        ret = regmap_update_bits(awi->regmap, AW9523_REG_PORT_MODE(pin),
                                 BIT(pin), (fsel ? BIT(pin) : 0));
        mutex_unlock(&awi->i2c_lock);
        return ret;
}

static const struct pinmux_ops aw9523_pinmux_ops = {
        .get_functions_count    = aw9523_pmx_get_funcs_count,
        .get_function_name      = aw9523_pmx_get_fname,
        .get_function_groups    = aw9523_pmx_get_groups,
        .set_mux                = aw9523_pmx_set_mux,
};

static int aw9523_pcfg_param_to_reg(enum pin_config_param pcp, int pin, u8 *r)
{
        u8 reg;

        switch (pcp) {
        case PIN_CONFIG_BIAS_PULL_PIN_DEFAULT:
        case PIN_CONFIG_BIAS_PULL_DOWN:
        case PIN_CONFIG_BIAS_PULL_UP:
                reg = AW9523_REG_IN_STATE(pin);
                break;
        case PIN_CONFIG_DRIVE_OPEN_DRAIN:
        case PIN_CONFIG_DRIVE_PUSH_PULL:
                reg = AW9523_REG_GCR;
                break;
        case PIN_CONFIG_INPUT_ENABLE:
        case PIN_CONFIG_OUTPUT_ENABLE:
                reg = AW9523_REG_CONF_STATE(pin);
                break;
        case PIN_CONFIG_LEVEL:
                reg = AW9523_REG_OUT_STATE(pin);
                break;
        default:
                return -ENOTSUPP;
        }
        *r = reg;

        return 0;
}

static int aw9523_pconf_get(struct pinctrl_dev *pctldev, unsigned int pin,
                            unsigned long *config)
{
        struct aw9523 *awi = pinctrl_dev_get_drvdata(pctldev);
        enum pin_config_param param = pinconf_to_config_param(*config);
        int regbit = pin % AW9523_PINS_PER_PORT;
        unsigned int val;
        u8 reg;
        int rc;

        rc = aw9523_pcfg_param_to_reg(param, pin, &reg);
        if (rc)
                return rc;

        mutex_lock(&awi->i2c_lock);
        rc = regmap_read(awi->regmap, reg, &val);
        mutex_unlock(&awi->i2c_lock);
        if (rc)
                return rc;

        switch (param) {
        case PIN_CONFIG_BIAS_PULL_UP:
        case PIN_CONFIG_INPUT_ENABLE:
        case PIN_CONFIG_LEVEL:
                val &= BIT(regbit);
                break;
        case PIN_CONFIG_BIAS_PULL_DOWN:
        case PIN_CONFIG_OUTPUT_ENABLE:
                val &= BIT(regbit);
                val = !val;
                break;
        case PIN_CONFIG_DRIVE_OPEN_DRAIN:
                if (pin >= AW9523_PINS_PER_PORT)
                        val = 0;
                else
                        val = !FIELD_GET(AW9523_GCR_GPOMD_MASK, val);
                break;
        case PIN_CONFIG_DRIVE_PUSH_PULL:
                if (pin >= AW9523_PINS_PER_PORT)
                        val = 1;
                else
                        val = FIELD_GET(AW9523_GCR_GPOMD_MASK, val);
                break;
        default:
                return -ENOTSUPP;
        }
        if (val < 1)
                return -EINVAL;

        *config = pinconf_to_config_packed(param, !!val);

        return rc;
}

static int aw9523_pconf_set(struct pinctrl_dev *pctldev, unsigned int pin,
                            unsigned long *configs, unsigned int num_configs)
{
        struct aw9523 *awi = pinctrl_dev_get_drvdata(pctldev);
        enum pin_config_param param;
        int regbit = pin % AW9523_PINS_PER_PORT;
        u32 arg;
        u8 reg;
        unsigned int mask, val;
        int i, rc;

        guard(mutex)(&awi->i2c_lock);
        for (i = 0; i < num_configs; i++) {
                param = pinconf_to_config_param(configs[i]);
                arg = pinconf_to_config_argument(configs[i]);

                rc = aw9523_pcfg_param_to_reg(param, pin, &reg);
                if (rc)
                        return rc;

                switch (param) {
                case PIN_CONFIG_LEVEL:
                        /* First, enable pin output */
                        rc = regmap_update_bits(awi->regmap,
                                                AW9523_REG_CONF_STATE(pin),
                                                BIT(regbit), 0);
                        if (rc)
                                return rc;

                        /* Then, fall through to config output level */
                        fallthrough;
                case PIN_CONFIG_OUTPUT_ENABLE:
                        arg = !arg;
                        fallthrough;
                case PIN_CONFIG_BIAS_PULL_PIN_DEFAULT:
                case PIN_CONFIG_BIAS_PULL_DOWN:
                case PIN_CONFIG_BIAS_PULL_UP:
                case PIN_CONFIG_INPUT_ENABLE:
                        mask = BIT(regbit);
                        val = arg ? BIT(regbit) : 0;
                        break;
                case PIN_CONFIG_DRIVE_OPEN_DRAIN:
                        /* Open-Drain is supported only on port 0 */
                        if (pin >= AW9523_PINS_PER_PORT)
                                return -ENOTSUPP;

                        mask = AW9523_GCR_GPOMD_MASK;
                        val = 0;
                        break;
                case PIN_CONFIG_DRIVE_PUSH_PULL:
                        /* Port 1 is always Push-Pull */
                        if (pin >= AW9523_PINS_PER_PORT) {
                                mask = 0;
                                val = 0;
                                continue;
                        }
                        mask = AW9523_GCR_GPOMD_MASK;
                        val = AW9523_GCR_GPOMD_MASK;
                        break;
                default:
                        return -ENOTSUPP;
                }

                rc = regmap_update_bits(awi->regmap, reg, mask, val);
                if (rc)
                        return rc;
        }

        return 0;
}

static const struct pinconf_ops aw9523_pinconf_ops = {
        .pin_config_get = aw9523_pconf_get,
        .pin_config_set = aw9523_pconf_set,
        .is_generic = true,
};

/*
 * aw9523_get_pin_direction - Get pin direction
 * @regmap: Regmap structure
 * @pin: gpiolib pin number
 * @n:   pin index in port register
 *
 * Return: Pin direction for success or negative number for error
 */
static int aw9523_get_pin_direction(struct regmap *regmap, u8 pin, u8 n)
{
        int ret;

        ret = regmap_test_bits(regmap, AW9523_REG_CONF_STATE(pin), BIT(n));
        if (ret < 0)
                return ret;

        return ret ? GPIO_LINE_DIRECTION_IN : GPIO_LINE_DIRECTION_OUT;
}

/*
 * aw9523_get_port_state - Get input or output state for entire port
 * @regmap: Regmap structure
 * @pin:    gpiolib pin number
 * @regbit: hw pin index, used to retrieve port number
 * @state:  returned port state
 *
 * Return: Zero for success or negative number for error
 */
static int aw9523_get_port_state(struct regmap *regmap, u8 pin, u8 regbit,
                                 unsigned int *state)
{
        u8 reg;
        int dir;

        dir = aw9523_get_pin_direction(regmap, pin, regbit);
        if (dir < 0)
                return dir;

        if (dir == GPIO_LINE_DIRECTION_IN)
                reg = AW9523_REG_IN_STATE(pin);
        else
                reg = AW9523_REG_OUT_STATE(pin);

        return regmap_read(regmap, reg, state);
}

static int aw9523_gpio_irq_type(struct irq_data *d, unsigned int type)
{
        switch (type) {
        case IRQ_TYPE_NONE:
        case IRQ_TYPE_EDGE_BOTH:
                return 0;
        default:
                return -EINVAL;
        };
}

/*
 * aw9523_irq_mask - Mask interrupt
 * @d: irq data
 *
 * Sets which interrupt to mask in the bitmap;
 * The interrupt will be masked when unlocking the irq bus.
 */
static void aw9523_irq_mask(struct irq_data *d)
{
        struct aw9523 *awi = gpiochip_get_data(irq_data_get_irq_chip_data(d));
        irq_hw_number_t hwirq = irqd_to_hwirq(d);
        unsigned int n = hwirq % AW9523_PINS_PER_PORT;

        regmap_update_bits(awi->regmap, AW9523_REG_INTR_DIS(hwirq),
                           BIT(n), BIT(n));
        gpiochip_disable_irq(&awi->gpio, hwirq);
}

/*
 * aw9523_irq_unmask - Unmask interrupt
 * @d: irq data
 *
 * Sets which interrupt to unmask in the bitmap;
 * The interrupt will be masked when unlocking the irq bus.
 */
static void aw9523_irq_unmask(struct irq_data *d)
{
        struct aw9523 *awi = gpiochip_get_data(irq_data_get_irq_chip_data(d));
        irq_hw_number_t hwirq = irqd_to_hwirq(d);
        unsigned int n = hwirq % AW9523_PINS_PER_PORT;

        gpiochip_enable_irq(&awi->gpio, hwirq);
        regmap_update_bits(awi->regmap, AW9523_REG_INTR_DIS(hwirq),
                           BIT(n), 0);
}

static irqreturn_t aw9523_irq_thread_func(int irq, void *dev_id)
{
        struct aw9523 *awi = (struct aw9523 *)dev_id;
        unsigned long n, val = 0;
        unsigned long changed_gpio;
        unsigned int tmp, port_pin, i, ret;

        for (i = 0; i < AW9523_NUM_PORTS; i++) {
                port_pin = i * AW9523_PINS_PER_PORT;
                ret = regmap_read(awi->regmap,
                                  AW9523_REG_IN_STATE(port_pin),
                                  &tmp);
                if (ret)
                        return ret;
                val |= (u8)tmp << (i * 8);
        }

        /* Handle GPIO input release interrupt as well */
        changed_gpio = awi->irq->cached_gpio ^ val;
        awi->irq->cached_gpio = val;

        /*
         * To avoid up to four *slow* i2c reads from any driver hooked
         * up to our interrupts, just check for the irq_find_mapping
         * result: if the interrupt is not mapped, then we don't want
         * to care about it.
         */
        for_each_set_bit(n, &changed_gpio, awi->gpio.ngpio) {
                tmp = irq_find_mapping(awi->gpio.irq.domain, n);
                if (tmp <= 0)
                        continue;
                handle_nested_irq(tmp);
        }

        return IRQ_HANDLED;
}

/*
 * aw9523_irq_bus_lock - Grab lock for interrupt operation
 * @d: irq data
 */
static void aw9523_irq_bus_lock(struct irq_data *d)
{
        struct aw9523 *awi = gpiochip_get_data(irq_data_get_irq_chip_data(d));

        mutex_lock(&awi->irq->lock);
        regcache_cache_only(awi->regmap, true);
}

/*
 * aw9523_irq_bus_sync_unlock - Synchronize state and unlock
 * @d: irq data
 *
 * Writes the interrupt mask bits (found in the bit map) to the
 * hardware, then unlocks the bus.
 */
static void aw9523_irq_bus_sync_unlock(struct irq_data *d)
{
        struct aw9523 *awi = gpiochip_get_data(irq_data_get_irq_chip_data(d));

        regcache_cache_only(awi->regmap, false);
        regcache_sync(awi->regmap);
        mutex_unlock(&awi->irq->lock);
}

static int aw9523_gpio_get_direction(struct gpio_chip *chip,
                                     unsigned int offset)
{
        struct aw9523 *awi = gpiochip_get_data(chip);
        u8 regbit = offset % AW9523_PINS_PER_PORT;
        int ret;

        mutex_lock(&awi->i2c_lock);
        ret = aw9523_get_pin_direction(awi->regmap, offset, regbit);
        mutex_unlock(&awi->i2c_lock);

        return ret;
}

static int aw9523_gpio_get(struct gpio_chip *chip, unsigned int offset)
{
        struct aw9523 *awi = gpiochip_get_data(chip);
        u8 regbit = offset % AW9523_PINS_PER_PORT;
        unsigned int val;
        int ret;

        mutex_lock(&awi->i2c_lock);
        ret = aw9523_get_port_state(awi->regmap, offset, regbit, &val);
        mutex_unlock(&awi->i2c_lock);
        if (ret)
                return ret;

        return !!(val & BIT(regbit));
}

/**
 * _aw9523_gpio_get_multiple - Get I/O state for an entire port
 * @awi: Controller data
 * @regbit: hw pin index, used to retrieve port number
 * @state: returned port I/O state
 * @mask: lines to read values for
 *
 * Return: Zero for success or negative number for error
 */
static int _aw9523_gpio_get_multiple(struct aw9523 *awi, u8 regbit,
                                     u8 *state, u8 mask)
{
        u32 dir_in, val;
        u8 m;
        int ret;

        /* Registers are 8-bits wide */
        ret = regmap_read(awi->regmap, AW9523_REG_CONF_STATE(regbit), &dir_in);
        if (ret)
                return ret;
        *state = 0;

        m = mask & dir_in;
        if (m) {
                ret = regmap_read(awi->regmap, AW9523_REG_IN_STATE(regbit),
                                  &val);
                if (ret)
                        return ret;
                *state |= (u8)val & m;
        }

        m = mask & ~dir_in;
        if (m) {
                ret = regmap_read(awi->regmap, AW9523_REG_OUT_STATE(regbit),
                                  &val);
                if (ret)
                        return ret;
                *state |= (u8)val & m;
        }

        return 0;
}

static int aw9523_gpio_get_multiple(struct gpio_chip *chip,
                                    unsigned long *mask,
                                    unsigned long *bits)
{
        struct aw9523 *awi = gpiochip_get_data(chip);
        u8 m, state = 0;
        int ret;

        guard(mutex)(&awi->i2c_lock);

        /* Port 0 (gpio 0-7) */
        m = *mask;
        if (m) {
                ret = _aw9523_gpio_get_multiple(awi, 0, &state, m);
                if (ret)
                        return ret;
        }
        *bits = state;

        /* Port 1 (gpio 8-15) */
        m = *mask >> 8;
        if (m) {
                ret = _aw9523_gpio_get_multiple(awi, AW9523_PINS_PER_PORT,
                                                &state, m);
                if (ret)
                        return ret;

                *bits |= (state << 8);
        }

        return 0;
}

static int aw9523_gpio_set_multiple(struct gpio_chip *chip,
                                    unsigned long *mask,
                                    unsigned long *bits)
{
        struct aw9523 *awi = gpiochip_get_data(chip);
        u8 mask_lo, mask_hi, bits_lo, bits_hi;
        unsigned int reg;
        int ret;

        mask_lo = *mask;
        mask_hi = *mask >> 8;
        bits_lo = *bits;
        bits_hi = *bits >> 8;

        guard(mutex)(&awi->i2c_lock);
        if (mask_hi) {
                reg = AW9523_REG_OUT_STATE(AW9523_PINS_PER_PORT);
                ret = regmap_write_bits(awi->regmap, reg, mask_hi, bits_hi);
                if (ret)
                        return ret;
        }
        if (mask_lo) {
                reg = AW9523_REG_OUT_STATE(0);
                ret = regmap_write_bits(awi->regmap, reg, mask_lo, bits_lo);
                if (ret)
                        return ret;
        }

        return 0;
}

static int aw9523_gpio_set(struct gpio_chip *chip, unsigned int offset,
                           int value)
{
        struct aw9523 *awi = gpiochip_get_data(chip);
        u8 regbit = offset % AW9523_PINS_PER_PORT;
        int ret;

        mutex_lock(&awi->i2c_lock);
        ret = regmap_update_bits(awi->regmap, AW9523_REG_OUT_STATE(offset),
                                 BIT(regbit), value ? BIT(regbit) : 0);
        mutex_unlock(&awi->i2c_lock);

        return ret;
}


static int aw9523_direction_input(struct gpio_chip *chip, unsigned int offset)
{
        struct aw9523 *awi = gpiochip_get_data(chip);
        u8 regbit = offset % AW9523_PINS_PER_PORT;
        int ret;

        mutex_lock(&awi->i2c_lock);
        ret = regmap_update_bits(awi->regmap, AW9523_REG_CONF_STATE(offset),
                                 BIT(regbit), BIT(regbit));
        mutex_unlock(&awi->i2c_lock);

        return ret;
}

static int aw9523_direction_output(struct gpio_chip *chip,
                                   unsigned int offset, int value)
{
        struct aw9523 *awi = gpiochip_get_data(chip);
        u8 regbit = offset % AW9523_PINS_PER_PORT;
        int ret;

        guard(mutex)(&awi->i2c_lock);
        ret = regmap_update_bits(awi->regmap, AW9523_REG_OUT_STATE(offset),
                                 BIT(regbit), value ? BIT(regbit) : 0);
        if (ret)
                return ret;

        ret = regmap_update_bits(awi->regmap, AW9523_REG_CONF_STATE(offset),
                                 BIT(regbit), 0);

        return ret;
}

static int aw9523_drive_reset_gpio(struct aw9523 *awi)
{
        unsigned int chip_id;
        int ret;

        /*
         * If the chip is already configured for any reason, then we
         * will probably succeed in sending the soft reset signal to
         * the hardware through I2C: this operation takes less time
         * compared to a full HW reset and it gives the same results.
         */
        ret = regmap_write(awi->regmap, AW9523_REG_SOFT_RESET, 0);
        if (ret == 0)
                goto done;

        dev_dbg(awi->dev, "Cannot execute soft reset: trying hard reset\n");
        ret = gpiod_direction_output(awi->reset_gpio, 0);
        if (ret)
                return ret;

        /* The reset pulse has to be longer than 20uS due to deglitch */
        usleep_range(AW9523_HW_RESET_US, AW9523_HW_RESET_US + 1);

        ret = gpiod_direction_output(awi->reset_gpio, 1);
        if (ret)
                return ret;
done:
        /* The HW needs at least 1uS to reliably recover after reset */
        usleep_range(AW9523_HW_RESET_RECOVERY_US,
                     AW9523_HW_RESET_RECOVERY_US + 1);

        /* Check the ChipID */
        ret = regmap_read(awi->regmap, AW9523_REG_CHIPID, &chip_id);
        if (ret) {
                dev_err(awi->dev, "Cannot read Chip ID: %d\n", ret);
                return ret;
        }
        if (chip_id != AW9523_VAL_EXPECTED_CHIPID) {
                dev_err(awi->dev, "Bad ChipID; read 0x%x, expected 0x%x\n",
                        chip_id, AW9523_VAL_EXPECTED_CHIPID);
                return -EINVAL;
        }

        return 0;
}

static int aw9523_hw_reset(struct aw9523 *awi)
{
        int ret, max_retries = 2;

        /* Sometimes the chip needs more than one reset cycle */
        do {
                ret = aw9523_drive_reset_gpio(awi);
                if (ret == 0)
                        break;
                max_retries--;
        } while (max_retries);

        return ret;
}

static int aw9523_init_gpiochip(struct aw9523 *awi, unsigned int npins)
{
        struct device *dev = awi->dev;
        struct gpio_chip *gc = &awi->gpio;

        gc->label = devm_kstrdup(dev, dev_name(dev), GFP_KERNEL);
        if (!gc->label)
                return -ENOMEM;

        gc->base = -1;
        gc->ngpio = npins;
        gc->get_direction = aw9523_gpio_get_direction;
        gc->direction_input = aw9523_direction_input;
        gc->direction_output = aw9523_direction_output;
        gc->get = aw9523_gpio_get;
        gc->get_multiple = aw9523_gpio_get_multiple;
        gc->set = aw9523_gpio_set;
        gc->set_multiple = aw9523_gpio_set_multiple;
        gc->set_config = gpiochip_generic_config;
        gc->parent = dev;
        gc->owner = THIS_MODULE;
        gc->can_sleep = true;

        return 0;
}

static const struct irq_chip aw9523_irq_chip = {
        .name = "aw9523",
        .irq_mask = aw9523_irq_mask,
        .irq_unmask = aw9523_irq_unmask,
        .irq_bus_lock = aw9523_irq_bus_lock,
        .irq_bus_sync_unlock = aw9523_irq_bus_sync_unlock,
        .irq_set_type = aw9523_gpio_irq_type,
        .flags = IRQCHIP_IMMUTABLE,
        GPIOCHIP_IRQ_RESOURCE_HELPERS,
};

static int aw9523_init_irq(struct aw9523 *awi, int irq)
{
        struct device *dev = awi->dev;
        struct gpio_irq_chip *girq;
        int ret;

        if (!device_property_read_bool(dev, "interrupt-controller"))
                return 0;

        awi->irq = devm_kzalloc(dev, sizeof(*awi->irq), GFP_KERNEL);
        if (!awi->irq)
                return -ENOMEM;

        mutex_init(&awi->irq->lock);

        ret = devm_request_threaded_irq(dev, irq, NULL, aw9523_irq_thread_func,
                                        IRQF_ONESHOT, dev_name(dev), awi);
        if (ret)
                return dev_err_probe(dev, ret, "Failed to request irq %d\n", irq);

        girq = &awi->gpio.irq;
        gpio_irq_chip_set_chip(girq, &aw9523_irq_chip);
        girq->parent_handler = NULL;
        girq->num_parents = 0;
        girq->parents = NULL;
        girq->default_type = IRQ_TYPE_EDGE_BOTH;
        girq->handler = handle_simple_irq;
        girq->threaded = true;

        return 0;
}

static bool aw9523_is_reg_hole(unsigned int reg)
{
        return (reg > AW9523_REG_PORT_MODE(AW9523_PINS_PER_PORT) &&
                reg < AW9523_REG_SOFT_RESET) ||
               (reg > AW9523_REG_INTR_DIS(AW9523_PINS_PER_PORT) &&
                reg < AW9523_REG_CHIPID);
}

static bool aw9523_readable_reg(struct device *dev, unsigned int reg)
{
        /* All available registers (minus holes) can be read */
        return !aw9523_is_reg_hole(reg);
}

static bool aw9523_volatile_reg(struct device *dev, unsigned int reg)
{
        return aw9523_is_reg_hole(reg) ||
               reg == AW9523_REG_IN_STATE(0) ||
               reg == AW9523_REG_IN_STATE(AW9523_PINS_PER_PORT) ||
               reg == AW9523_REG_CHIPID ||
               reg == AW9523_REG_SOFT_RESET;
}

static bool aw9523_writeable_reg(struct device *dev, unsigned int reg)
{
        return !aw9523_is_reg_hole(reg) && reg != AW9523_REG_CHIPID;
}

static bool aw9523_precious_reg(struct device *dev, unsigned int reg)
{
        /* Reading AW9523_REG_IN_STATE clears interrupt status */
        return aw9523_is_reg_hole(reg) ||
               reg == AW9523_REG_IN_STATE(0) ||
               reg == AW9523_REG_IN_STATE(AW9523_PINS_PER_PORT);
}

static const struct regmap_config aw9523_regmap = {
        .reg_bits = 8,
        .val_bits = 8,
        .reg_stride = 1,

        .precious_reg = aw9523_precious_reg,
        .readable_reg = aw9523_readable_reg,
        .volatile_reg = aw9523_volatile_reg,
        .writeable_reg = aw9523_writeable_reg,

        .cache_type = REGCACHE_FLAT,
        .disable_locking = true,

        .num_reg_defaults_raw = AW9523_REG_SOFT_RESET,
};

static int aw9523_hw_init(struct aw9523 *awi)
{
        u8 p1_pin = AW9523_PINS_PER_PORT;
        unsigned int val;
        int ret;

        /* No register caching during initialization */
        regcache_cache_bypass(awi->regmap, true);

        /* Bring up the chip */
        ret = aw9523_hw_reset(awi);
        if (ret) {
                dev_err(awi->dev, "HW Reset failed: %d\n", ret);
                return ret;
        }

        /*
         * This is the expected chip and it is running: it's time to
         * set a safe default configuration in case the user doesn't
         * configure (all of the available) pins in this chip.
         * P.S.: The writes order doesn't matter.
         */

        /* Set all pins as GPIO */
        ret = regmap_write(awi->regmap, AW9523_REG_PORT_MODE(0), U8_MAX);
        if (ret)
                return ret;
        ret = regmap_write(awi->regmap, AW9523_REG_PORT_MODE(p1_pin), U8_MAX);
        if (ret)
                return ret;

        /* Set Open-Drain mode on Port 0 (Port 1 is always P-P) */
        ret = regmap_write(awi->regmap, AW9523_REG_GCR, 0);
        if (ret)
                return ret;

        /* Set all pins as inputs */
        ret = regmap_write(awi->regmap, AW9523_REG_CONF_STATE(0), U8_MAX);
        if (ret)
                return ret;
        ret = regmap_write(awi->regmap, AW9523_REG_CONF_STATE(p1_pin), U8_MAX);
        if (ret)
                return ret;

        /* Disable all interrupts to avoid unreasoned wakeups */
        ret = regmap_write(awi->regmap, AW9523_REG_INTR_DIS(0), U8_MAX);
        if (ret)
                return ret;
        ret = regmap_write(awi->regmap, AW9523_REG_INTR_DIS(p1_pin), U8_MAX);
        if (ret)
                return ret;

        /* Clear setup-generated interrupts by performing a port state read */
        ret = aw9523_get_port_state(awi->regmap, 0, 0, &val);
        if (ret)
                return ret;
        ret = aw9523_get_port_state(awi->regmap, p1_pin, 0, &val);
        if (ret)
                return ret;

        /* Everything went fine: activate and reinitialize register cache */
        regcache_cache_bypass(awi->regmap, false);
        return regmap_reinit_cache(awi->regmap, &aw9523_regmap);
}

static int aw9523_probe(struct i2c_client *client)
{
        struct device *dev = &client->dev;
        struct pinctrl_desc *pdesc;
        struct aw9523 *awi;
        int ret;

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

        i2c_set_clientdata(client, awi);

        awi->dev = dev;
        awi->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
        if (IS_ERR(awi->reset_gpio))
                return PTR_ERR(awi->reset_gpio);
        gpiod_set_consumer_name(awi->reset_gpio, "aw9523 reset");

        awi->regmap = devm_regmap_init_i2c(client, &aw9523_regmap);
        if (IS_ERR(awi->regmap))
                return PTR_ERR(awi->regmap);

        awi->vio_vreg = devm_regulator_get_enable_optional(dev, "vio");
        if (awi->vio_vreg && awi->vio_vreg != -ENODEV)
                return awi->vio_vreg;

        ret = devm_mutex_init(dev, &awi->i2c_lock);
        if (ret)
                return ret;

        lockdep_set_subclass(&awi->i2c_lock, i2c_adapter_depth(client->adapter));

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

        ret = aw9523_hw_init(awi);
        if (ret)
                return ret;

        pdesc->name = dev_name(dev);
        pdesc->owner = THIS_MODULE;
        pdesc->pctlops = &aw9523_pinctrl_ops;
        pdesc->pmxops  = &aw9523_pinmux_ops;
        pdesc->confops = &aw9523_pinconf_ops;
        pdesc->pins = aw9523_pins;
        pdesc->npins = ARRAY_SIZE(aw9523_pins);

        ret = aw9523_init_gpiochip(awi, pdesc->npins);
        if (ret)
                return ret;

        if (client->irq) {
                ret = aw9523_init_irq(awi, client->irq);
                if (ret)
                        return ret;
        }

        awi->pctl = devm_pinctrl_register(dev, pdesc, awi);
        if (IS_ERR(awi->pctl))
                return dev_err_probe(dev, PTR_ERR(awi->pctl),
                                     "Cannot register pinctrl");

        return devm_gpiochip_add_data(dev, &awi->gpio, awi);
}

static void aw9523_remove(struct i2c_client *client)
{
        struct aw9523 *awi = i2c_get_clientdata(client);

        /*
         * If the chip VIO is connected to a regulator that we can turn
         * off, life is easy... otherwise, reinitialize the chip and
         * set the pins to hardware defaults before removing the driver
         * to leave it in a clean, safe and predictable state.
         */
        if (awi->vio_vreg == -ENODEV) {
                mutex_lock(&awi->i2c_lock);
                aw9523_hw_init(awi);
                mutex_unlock(&awi->i2c_lock);
        }
}

static const struct i2c_device_id aw9523_i2c_id_table[] = {
        { .name = "aw9523_i2c" },
        { }
};
MODULE_DEVICE_TABLE(i2c, aw9523_i2c_id_table);

static const struct of_device_id of_aw9523_i2c_match[] = {
        { .compatible = "awinic,aw9523-pinctrl", },
        { }
};
MODULE_DEVICE_TABLE(of, of_aw9523_i2c_match);

static struct i2c_driver aw9523_driver = {
        .driver = {
                .name = "aw9523-pinctrl",
                .of_match_table = of_aw9523_i2c_match,
        },
        .probe = aw9523_probe,
        .remove = aw9523_remove,
        .id_table = aw9523_i2c_id_table,
};
module_i2c_driver(aw9523_driver);

MODULE_DESCRIPTION("Awinic AW9523 I2C GPIO Expander driver");
MODULE_AUTHOR("AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>");
MODULE_LICENSE("GPL v2");