// SPDX-License-Identifier: GPL-2.0
/*
 * GPIO library for the ACCES IDIO-16 family
 * Copyright (C) 2022 William Breathitt Gray
 */

#define DEFAULT_SYMBOL_NAMESPACE "GPIO_IDIO_16"

#include <linux/bitmap.h>
#include <linux/bits.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/gpio/regmap.h>
#include <linux/module.h>
#include <linux/regmap.h>
#include <linux/types.h>

#include "gpio-idio-16.h"

#define IDIO_16_DAT_BASE 0x0
#define IDIO_16_OUT_BASE IDIO_16_DAT_BASE
#define IDIO_16_IN_BASE (IDIO_16_DAT_BASE + 1)
#define IDIO_16_CLEAR_INTERRUPT 0x1
#define IDIO_16_ENABLE_IRQ 0x2
#define IDIO_16_DEACTIVATE_INPUT_FILTERS 0x3
#define IDIO_16_DISABLE_IRQ IDIO_16_ENABLE_IRQ
#define IDIO_16_INTERRUPT_STATUS 0x6

#define IDIO_16_NGPIO 32
#define IDIO_16_NGPIO_PER_REG 8
#define IDIO_16_REG_STRIDE 4

struct idio_16_data {
        struct regmap *map;
        unsigned int irq_mask;
};

static int idio_16_handle_mask_sync(const int index, const unsigned int mask_buf_def,
                                    const unsigned int mask_buf, void *const irq_drv_data)
{
        struct idio_16_data *const data = irq_drv_data;
        const unsigned int prev_mask = data->irq_mask;
        int err;
        unsigned int val;

        /* exit early if no change since the previous mask */
        if (mask_buf == prev_mask)
                return 0;

        /* remember the current mask for the next mask sync */
        data->irq_mask = mask_buf;

        /* if all previously masked, enable interrupts when unmasking */
        if (prev_mask == mask_buf_def) {
                err = regmap_write(data->map, IDIO_16_CLEAR_INTERRUPT, 0x00);
                if (err)
                        return err;
                return regmap_read(data->map, IDIO_16_ENABLE_IRQ, &val);
        }

        /* if all are currently masked, disable interrupts */
        if (mask_buf == mask_buf_def)
                return regmap_write(data->map, IDIO_16_DISABLE_IRQ, 0x00);

        return 0;
}

static int idio_16_reg_mask_xlate(struct gpio_regmap *const gpio, const unsigned int base,
                                  const unsigned int offset, unsigned int *const reg,
                                  unsigned int *const mask)
{
        unsigned int stride;

        /* Input lines start at GPIO 16 */
        if (offset < 16) {
                stride = offset / IDIO_16_NGPIO_PER_REG;
                *reg = IDIO_16_OUT_BASE + stride * IDIO_16_REG_STRIDE;
        } else {
                stride = (offset - 16) / IDIO_16_NGPIO_PER_REG;
                *reg = IDIO_16_IN_BASE + stride * IDIO_16_REG_STRIDE;
        }

        *mask = BIT(offset % IDIO_16_NGPIO_PER_REG);

        return 0;
}

static const char *idio_16_names[IDIO_16_NGPIO] = {
        "OUT0", "OUT1", "OUT2", "OUT3", "OUT4", "OUT5", "OUT6", "OUT7",
        "OUT8", "OUT9", "OUT10", "OUT11", "OUT12", "OUT13", "OUT14", "OUT15",
        "IIN0", "IIN1", "IIN2", "IIN3", "IIN4", "IIN5", "IIN6", "IIN7",
        "IIN8", "IIN9", "IIN10", "IIN11", "IIN12", "IIN13", "IIN14", "IIN15",
};

/**
 * devm_idio_16_regmap_register - Register an IDIO-16 GPIO device
 * @dev:        device that is registering this IDIO-16 GPIO device
 * @config:     configuration for idio_16_regmap_config
 *
 * Registers an IDIO-16 GPIO device. Returns 0 on success and negative error number on failure.
 */
int devm_idio_16_regmap_register(struct device *const dev,
                                 const struct idio_16_regmap_config *const config)
{
        struct gpio_regmap_config gpio_config = {};
        int err;
        struct idio_16_data *data;
        struct regmap_irq_chip *chip;
        struct regmap_irq_chip_data *chip_data;
        DECLARE_BITMAP(fixed_direction_output, IDIO_16_NGPIO);

        if (!config->parent)
                return -EINVAL;

        if (!config->map)
                return -EINVAL;

        if (!config->regmap_irqs)
                return -EINVAL;

        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;
        data->map = config->map;

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

        chip->name = dev_name(dev);
        chip->status_base = IDIO_16_INTERRUPT_STATUS;
        chip->mask_base = IDIO_16_ENABLE_IRQ;
        chip->ack_base = IDIO_16_CLEAR_INTERRUPT;
        chip->no_status = config->no_status;
        chip->num_regs = 1;
        chip->irqs = config->regmap_irqs;
        chip->num_irqs = config->num_regmap_irqs;
        chip->handle_mask_sync = idio_16_handle_mask_sync;
        chip->irq_drv_data = data;

        /* Disable IRQ to prevent spurious interrupts before we're ready */
        err = regmap_write(data->map, IDIO_16_DISABLE_IRQ, 0x00);
        if (err)
                return err;

        err = devm_regmap_add_irq_chip(dev, data->map, config->irq, 0, 0, chip, &chip_data);
        if (err)
                return dev_err_probe(dev, err, "IRQ registration failed\n");

        if (config->filters) {
                /* Deactivate input filters */
                err = regmap_write(data->map, IDIO_16_DEACTIVATE_INPUT_FILTERS, 0x00);
                if (err)
                        return err;
        }

        gpio_config.parent = config->parent;
        gpio_config.regmap = data->map;
        gpio_config.ngpio = IDIO_16_NGPIO;
        gpio_config.names = idio_16_names;
        gpio_config.reg_dat_base = GPIO_REGMAP_ADDR(IDIO_16_DAT_BASE);
        gpio_config.reg_set_base = GPIO_REGMAP_ADDR(IDIO_16_DAT_BASE);
        gpio_config.ngpio_per_reg = IDIO_16_NGPIO_PER_REG;
        gpio_config.reg_stride = IDIO_16_REG_STRIDE;
        gpio_config.irq_domain = regmap_irq_get_domain(chip_data);
        gpio_config.reg_mask_xlate = idio_16_reg_mask_xlate;

        bitmap_from_u64(fixed_direction_output, GENMASK_U64(15, 0));
        gpio_config.fixed_direction_output = fixed_direction_output;

        return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(dev, &gpio_config));
}
EXPORT_SYMBOL_GPL(devm_idio_16_regmap_register);

MODULE_AUTHOR("William Breathitt Gray");
MODULE_DESCRIPTION("ACCES IDIO-16 GPIO Library");
MODULE_LICENSE("GPL");