// SPDX-License-Identifier: GPL-2.0-only
/*
 * GPIO driver for the WinSystems WS16C48
 * Copyright (C) 2016 William Breathitt Gray
 */
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/gpio/driver.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/irqdesc.h>
#include <linux/isa.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/spinlock.h>

#define WS16C48_EXTENT 16
#define MAX_NUM_WS16C48 max_num_isa_dev(WS16C48_EXTENT)

static unsigned int base[MAX_NUM_WS16C48];
static unsigned int num_ws16c48;
module_param_hw_array(base, uint, ioport, &num_ws16c48, 0);
MODULE_PARM_DESC(base, "WinSystems WS16C48 base addresses");

static unsigned int irq[MAX_NUM_WS16C48];
module_param_hw_array(irq, uint, irq, NULL, 0);
MODULE_PARM_DESC(irq, "WinSystems WS16C48 interrupt line numbers");

/**
 * struct ws16c48_gpio - GPIO device private data structure
 * @chip:       instance of the gpio_chip
 * @io_state:   bit I/O state (whether bit is set to input or output)
 * @out_state:  output bits state
 * @lock:       synchronization lock to prevent I/O race conditions
 * @irq_mask:   I/O bits affected by interrupts
 * @flow_mask:  IRQ flow type mask for the respective I/O bits
 * @base:       base port address of the GPIO device
 */
struct ws16c48_gpio {
        struct gpio_chip chip;
        unsigned char io_state[6];
        unsigned char out_state[6];
        raw_spinlock_t lock;
        unsigned long irq_mask;
        unsigned long flow_mask;
        unsigned base;
};

static int ws16c48_gpio_get_direction(struct gpio_chip *chip, unsigned offset)
{
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        const unsigned port = offset / 8;
        const unsigned mask = BIT(offset % 8);

        if (ws16c48gpio->io_state[port] & mask)
                return GPIO_LINE_DIRECTION_IN;

        return GPIO_LINE_DIRECTION_OUT;
}

static int ws16c48_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
{
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        const unsigned port = offset / 8;
        const unsigned mask = BIT(offset % 8);
        unsigned long flags;

        raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);

        ws16c48gpio->io_state[port] |= mask;
        ws16c48gpio->out_state[port] &= ~mask;
        outb(ws16c48gpio->out_state[port], ws16c48gpio->base + port);

        raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);

        return 0;
}

static int ws16c48_gpio_direction_output(struct gpio_chip *chip,
        unsigned offset, int value)
{
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        const unsigned port = offset / 8;
        const unsigned mask = BIT(offset % 8);
        unsigned long flags;

        raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);

        ws16c48gpio->io_state[port] &= ~mask;
        if (value)
                ws16c48gpio->out_state[port] |= mask;
        else
                ws16c48gpio->out_state[port] &= ~mask;
        outb(ws16c48gpio->out_state[port], ws16c48gpio->base + port);

        raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);

        return 0;
}

static int ws16c48_gpio_get(struct gpio_chip *chip, unsigned offset)
{
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        const unsigned port = offset / 8;
        const unsigned mask = BIT(offset % 8);
        unsigned long flags;
        unsigned port_state;

        raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);

        /* ensure that GPIO is set for input */
        if (!(ws16c48gpio->io_state[port] & mask)) {
                raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
                return -EINVAL;
        }

        port_state = inb(ws16c48gpio->base + port);

        raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);

        return !!(port_state & mask);
}

static int ws16c48_gpio_get_multiple(struct gpio_chip *chip,
        unsigned long *mask, unsigned long *bits)
{
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        unsigned long offset;
        unsigned long gpio_mask;
        unsigned int port_addr;
        unsigned long port_state;

        /* clear bits array to a clean slate */
        bitmap_zero(bits, chip->ngpio);

        for_each_set_clump8(offset, gpio_mask, mask, chip->ngpio) {
                port_addr = ws16c48gpio->base + offset / 8;
                port_state = inb(port_addr) & gpio_mask;

                bitmap_set_value8(bits, port_state, offset);
        }

        return 0;
}

static void ws16c48_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
{
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        const unsigned port = offset / 8;
        const unsigned mask = BIT(offset % 8);
        unsigned long flags;

        raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);

        /* ensure that GPIO is set for output */
        if (ws16c48gpio->io_state[port] & mask) {
                raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
                return;
        }

        if (value)
                ws16c48gpio->out_state[port] |= mask;
        else
                ws16c48gpio->out_state[port] &= ~mask;
        outb(ws16c48gpio->out_state[port], ws16c48gpio->base + port);

        raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
}

static void ws16c48_gpio_set_multiple(struct gpio_chip *chip,
        unsigned long *mask, unsigned long *bits)
{
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        unsigned long offset;
        unsigned long gpio_mask;
        size_t index;
        unsigned int port_addr;
        unsigned long bitmask;
        unsigned long flags;

        for_each_set_clump8(offset, gpio_mask, mask, chip->ngpio) {
                index = offset / 8;
                port_addr = ws16c48gpio->base + index;

                /* mask out GPIO configured for input */
                gpio_mask &= ~ws16c48gpio->io_state[index];
                bitmask = bitmap_get_value8(bits, offset) & gpio_mask;

                raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);

                /* update output state data and set device gpio register */
                ws16c48gpio->out_state[index] &= ~gpio_mask;
                ws16c48gpio->out_state[index] |= bitmask;
                outb(ws16c48gpio->out_state[index], port_addr);

                raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
        }
}

static void ws16c48_irq_ack(struct irq_data *data)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        const unsigned long offset = irqd_to_hwirq(data);
        const unsigned port = offset / 8;
        const unsigned mask = BIT(offset % 8);
        unsigned long flags;
        unsigned port_state;

        /* only the first 3 ports support interrupts */
        if (port > 2)
                return;

        raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);

        port_state = ws16c48gpio->irq_mask >> (8*port);

        outb(0x80, ws16c48gpio->base + 7);
        outb(port_state & ~mask, ws16c48gpio->base + 8 + port);
        outb(port_state | mask, ws16c48gpio->base + 8 + port);
        outb(0xC0, ws16c48gpio->base + 7);

        raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
}

static void ws16c48_irq_mask(struct irq_data *data)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        const unsigned long offset = irqd_to_hwirq(data);
        const unsigned long mask = BIT(offset);
        const unsigned port = offset / 8;
        unsigned long flags;

        /* only the first 3 ports support interrupts */
        if (port > 2)
                return;

        raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);

        ws16c48gpio->irq_mask &= ~mask;

        outb(0x80, ws16c48gpio->base + 7);
        outb(ws16c48gpio->irq_mask >> (8*port), ws16c48gpio->base + 8 + port);
        outb(0xC0, ws16c48gpio->base + 7);

        raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
}

static void ws16c48_irq_unmask(struct irq_data *data)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        const unsigned long offset = irqd_to_hwirq(data);
        const unsigned long mask = BIT(offset);
        const unsigned port = offset / 8;
        unsigned long flags;

        /* only the first 3 ports support interrupts */
        if (port > 2)
                return;

        raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);

        ws16c48gpio->irq_mask |= mask;

        outb(0x80, ws16c48gpio->base + 7);
        outb(ws16c48gpio->irq_mask >> (8*port), ws16c48gpio->base + 8 + port);
        outb(0xC0, ws16c48gpio->base + 7);

        raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
}

static int ws16c48_irq_set_type(struct irq_data *data, unsigned flow_type)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
        struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
        const unsigned long offset = irqd_to_hwirq(data);
        const unsigned long mask = BIT(offset);
        const unsigned port = offset / 8;
        unsigned long flags;

        /* only the first 3 ports support interrupts */
        if (port > 2)
                return -EINVAL;

        raw_spin_lock_irqsave(&ws16c48gpio->lock, flags);

        switch (flow_type) {
        case IRQ_TYPE_NONE:
                break;
        case IRQ_TYPE_EDGE_RISING:
                ws16c48gpio->flow_mask |= mask;
                break;
        case IRQ_TYPE_EDGE_FALLING:
                ws16c48gpio->flow_mask &= ~mask;
                break;
        default:
                raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
                return -EINVAL;
        }

        outb(0x40, ws16c48gpio->base + 7);
        outb(ws16c48gpio->flow_mask >> (8*port), ws16c48gpio->base + 8 + port);
        outb(0xC0, ws16c48gpio->base + 7);

        raw_spin_unlock_irqrestore(&ws16c48gpio->lock, flags);

        return 0;
}

static struct irq_chip ws16c48_irqchip = {
        .name = "ws16c48",
        .irq_ack = ws16c48_irq_ack,
        .irq_mask = ws16c48_irq_mask,
        .irq_unmask = ws16c48_irq_unmask,
        .irq_set_type = ws16c48_irq_set_type
};

static irqreturn_t ws16c48_irq_handler(int irq, void *dev_id)
{
        struct ws16c48_gpio *const ws16c48gpio = dev_id;
        struct gpio_chip *const chip = &ws16c48gpio->chip;
        unsigned long int_pending;
        unsigned long port;
        unsigned long int_id;
        unsigned long gpio;

        int_pending = inb(ws16c48gpio->base + 6) & 0x7;
        if (!int_pending)
                return IRQ_NONE;

        /* loop until all pending interrupts are handled */
        do {
                for_each_set_bit(port, &int_pending, 3) {
                        int_id = inb(ws16c48gpio->base + 8 + port);
                        for_each_set_bit(gpio, &int_id, 8)
                                generic_handle_irq(irq_find_mapping(
                                        chip->irq.domain, gpio + 8*port));
                }

                int_pending = inb(ws16c48gpio->base + 6) & 0x7;
        } while (int_pending);

        return IRQ_HANDLED;
}

#define WS16C48_NGPIO 48
static const char *ws16c48_names[WS16C48_NGPIO] = {
        "Port 0 Bit 0", "Port 0 Bit 1", "Port 0 Bit 2", "Port 0 Bit 3",
        "Port 0 Bit 4", "Port 0 Bit 5", "Port 0 Bit 6", "Port 0 Bit 7",
        "Port 1 Bit 0", "Port 1 Bit 1", "Port 1 Bit 2", "Port 1 Bit 3",
        "Port 1 Bit 4", "Port 1 Bit 5", "Port 1 Bit 6", "Port 1 Bit 7",
        "Port 2 Bit 0", "Port 2 Bit 1", "Port 2 Bit 2", "Port 2 Bit 3",
        "Port 2 Bit 4", "Port 2 Bit 5", "Port 2 Bit 6", "Port 2 Bit 7",
        "Port 3 Bit 0", "Port 3 Bit 1", "Port 3 Bit 2", "Port 3 Bit 3",
        "Port 3 Bit 4", "Port 3 Bit 5", "Port 3 Bit 6", "Port 3 Bit 7",
        "Port 4 Bit 0", "Port 4 Bit 1", "Port 4 Bit 2", "Port 4 Bit 3",
        "Port 4 Bit 4", "Port 4 Bit 5", "Port 4 Bit 6", "Port 4 Bit 7",
        "Port 5 Bit 0", "Port 5 Bit 1", "Port 5 Bit 2", "Port 5 Bit 3",
        "Port 5 Bit 4", "Port 5 Bit 5", "Port 5 Bit 6", "Port 5 Bit 7"
};

static int ws16c48_probe(struct device *dev, unsigned int id)
{
        struct ws16c48_gpio *ws16c48gpio;
        const char *const name = dev_name(dev);
        int err;

        ws16c48gpio = devm_kzalloc(dev, sizeof(*ws16c48gpio), GFP_KERNEL);
        if (!ws16c48gpio)
                return -ENOMEM;

        if (!devm_request_region(dev, base[id], WS16C48_EXTENT, name)) {
                dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
                        base[id], base[id] + WS16C48_EXTENT);
                return -EBUSY;
        }

        ws16c48gpio->chip.label = name;
        ws16c48gpio->chip.parent = dev;
        ws16c48gpio->chip.owner = THIS_MODULE;
        ws16c48gpio->chip.base = -1;
        ws16c48gpio->chip.ngpio = WS16C48_NGPIO;
        ws16c48gpio->chip.names = ws16c48_names;
        ws16c48gpio->chip.get_direction = ws16c48_gpio_get_direction;
        ws16c48gpio->chip.direction_input = ws16c48_gpio_direction_input;
        ws16c48gpio->chip.direction_output = ws16c48_gpio_direction_output;
        ws16c48gpio->chip.get = ws16c48_gpio_get;
        ws16c48gpio->chip.get_multiple = ws16c48_gpio_get_multiple;
        ws16c48gpio->chip.set = ws16c48_gpio_set;
        ws16c48gpio->chip.set_multiple = ws16c48_gpio_set_multiple;
        ws16c48gpio->base = base[id];

        raw_spin_lock_init(&ws16c48gpio->lock);

        err = devm_gpiochip_add_data(dev, &ws16c48gpio->chip, ws16c48gpio);
        if (err) {
                dev_err(dev, "GPIO registering failed (%d)\n", err);
                return err;
        }

        /* Disable IRQ by default */
        outb(0x80, base[id] + 7);
        outb(0, base[id] + 8);
        outb(0, base[id] + 9);
        outb(0, base[id] + 10);
        outb(0xC0, base[id] + 7);

        err = gpiochip_irqchip_add(&ws16c48gpio->chip, &ws16c48_irqchip, 0,
                handle_edge_irq, IRQ_TYPE_NONE);
        if (err) {
                dev_err(dev, "Could not add irqchip (%d)\n", err);
                return err;
        }

        err = devm_request_irq(dev, irq[id], ws16c48_irq_handler, IRQF_SHARED,
                name, ws16c48gpio);
        if (err) {
                dev_err(dev, "IRQ handler registering failed (%d)\n", err);
                return err;
        }

        return 0;
}

static struct isa_driver ws16c48_driver = {
        .probe = ws16c48_probe,
        .driver = {
                .name = "ws16c48"
        },
};

module_isa_driver(ws16c48_driver, num_ws16c48);

MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
MODULE_DESCRIPTION("WinSystems WS16C48 GPIO driver");
MODULE_LICENSE("GPL v2");