// SPDX-License-Identifier: GPL-2.0-only
/*
 * Kontron PLD GPIO driver
 *
 * Copyright (c) 2010-2013 Kontron Europe GmbH
 * Author: Michael Brunner <michael.brunner@kontron.com>
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/gpio/driver.h>
#include <linux/mfd/kempld.h>

#define KEMPLD_GPIO_MAX_NUM             16
#define KEMPLD_GPIO_MASK(x)             (BIT((x) % 8))
#define KEMPLD_GPIO_DIR                 0x40
#define KEMPLD_GPIO_LVL                 0x42
#define KEMPLD_GPIO_STS                 0x44
#define KEMPLD_GPIO_EVT_LVL_EDGE        0x46
#define KEMPLD_GPIO_EVT_LOW_HIGH        0x48
#define KEMPLD_GPIO_IEN                 0x4A
#define KEMPLD_GPIO_OUT_LVL             0x4E

/* The IRQ to use if none was configured in the BIOS */
static unsigned int gpio_irq;
module_param_hw(gpio_irq, uint, irq, 0444);
MODULE_PARM_DESC(gpio_irq, "Set legacy GPIO IRQ (1-15)");

struct kempld_gpio_data {
        struct gpio_chip                chip;
        struct kempld_device_data       *pld;
        u8                              out_lvl_reg;

        struct mutex                    irq_lock;
        u16                             ien;
        u16                             evt_low_high;
        u16                             evt_lvl_edge;
};

/*
 * Set or clear GPIO bit
 * kempld_get_mutex must be called prior to calling this function.
 */
static void kempld_gpio_bitop(struct kempld_device_data *pld,
                              u8 reg, unsigned int bit, bool val)
{
        u8 status;

        status = kempld_read8(pld, reg + (bit / 8));
        if (val)
                status |= KEMPLD_GPIO_MASK(bit);
        else
                status &= ~KEMPLD_GPIO_MASK(bit);
        kempld_write8(pld, reg + (bit / 8), status);
}

static int kempld_gpio_get_bit(struct kempld_device_data *pld,
                               u8 reg, unsigned int bit)
{
        u8 status;

        kempld_get_mutex(pld);
        status = kempld_read8(pld, reg + (bit / 8));
        kempld_release_mutex(pld);

        return !!(status & KEMPLD_GPIO_MASK(bit));
}

static int kempld_gpio_get(struct gpio_chip *chip, unsigned offset)
{
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);
        struct kempld_device_data *pld = gpio->pld;

        return !!kempld_gpio_get_bit(pld, KEMPLD_GPIO_LVL, offset);
}

static int kempld_gpio_get_multiple(struct gpio_chip *chip, unsigned long *mask,
                                    unsigned long *bits)
{
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);
        struct kempld_device_data *pld = gpio->pld;
        u8 reg = KEMPLD_GPIO_LVL;
        unsigned int shift;

        bits[0] &= ~mask[0];

        kempld_get_mutex(pld);

        /* Try to reduce to a single 8 bits access if possible */
        for (shift = 0; shift < gpio->chip.ngpio; shift += 8, reg++) {
                unsigned long msk = (mask[0] >> shift) & 0xff;

                if (!msk)
                        continue;

                bits[0] |= (kempld_read8(pld, reg) & msk) << shift;
        }

        kempld_release_mutex(pld);

        return 0;
}

static int kempld_gpio_set(struct gpio_chip *chip, unsigned int offset,
                           int value)
{
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);
        struct kempld_device_data *pld = gpio->pld;

        kempld_get_mutex(pld);
        kempld_gpio_bitop(pld, gpio->out_lvl_reg, offset, value);
        kempld_release_mutex(pld);

        return 0;
}

static int kempld_gpio_set_multiple(struct gpio_chip *chip,
                                    unsigned long *mask, unsigned long *bits)
{
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);
        struct kempld_device_data *pld = gpio->pld;
        u8 reg = gpio->out_lvl_reg;
        unsigned int shift;

        kempld_get_mutex(pld);

        /* Try to reduce to a single 8 bits access if possible */
        for (shift = 0; shift < gpio->chip.ngpio; shift += 8, reg++) {
                u8 val, msk = mask[0] >> shift;

                if (!msk)
                        continue;

                if (msk != 0xFF)
                        val = kempld_read8(pld, reg) & ~msk;
                else
                        val = 0;

                val |= (bits[0] >> shift) & msk;
                kempld_write8(pld, reg, val);
        }

        kempld_release_mutex(pld);

        return 0;
}

static int kempld_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
{
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);
        struct kempld_device_data *pld = gpio->pld;

        kempld_get_mutex(pld);
        kempld_gpio_bitop(pld, KEMPLD_GPIO_DIR, offset, 0);
        kempld_release_mutex(pld);

        return 0;
}

static int kempld_gpio_direction_output(struct gpio_chip *chip, unsigned offset,
                                        int value)
{
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);
        struct kempld_device_data *pld = gpio->pld;

        kempld_get_mutex(pld);
        kempld_gpio_bitop(pld, gpio->out_lvl_reg, offset, value);
        kempld_gpio_bitop(pld, KEMPLD_GPIO_DIR, offset, 1);
        kempld_release_mutex(pld);

        return 0;
}

static int kempld_gpio_get_direction(struct gpio_chip *chip, unsigned offset)
{
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);
        struct kempld_device_data *pld = gpio->pld;

        if (kempld_gpio_get_bit(pld, KEMPLD_GPIO_DIR, offset))
                return GPIO_LINE_DIRECTION_OUT;

        return GPIO_LINE_DIRECTION_IN;
}

static int kempld_gpio_pincount(struct kempld_device_data *pld)
{
        u16 evt, evt_back;

        kempld_get_mutex(pld);

        /* Backup event register as it might be already initialized */
        evt_back = kempld_read16(pld, KEMPLD_GPIO_EVT_LVL_EDGE);
        /* Clear event register */
        kempld_write16(pld, KEMPLD_GPIO_EVT_LVL_EDGE, 0x0000);
        /* Read back event register */
        evt = kempld_read16(pld, KEMPLD_GPIO_EVT_LVL_EDGE);
        /* Restore event register */
        kempld_write16(pld, KEMPLD_GPIO_EVT_LVL_EDGE, evt_back);

        kempld_release_mutex(pld);

        return evt ? __ffs(evt) : 16;
}

static void kempld_irq_mask(struct irq_data *data)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);

        gpio->ien &= ~BIT(irqd_to_hwirq(data));
        gpiochip_disable_irq(chip, irqd_to_hwirq(data));
}

static void kempld_irq_unmask(struct irq_data *data)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);

        gpiochip_enable_irq(chip, irqd_to_hwirq(data));
        gpio->ien |= BIT(irqd_to_hwirq(data));
}

static int kempld_irq_set_type(struct irq_data *data, unsigned int type)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);

        switch (type) {
        case IRQ_TYPE_EDGE_RISING:
                gpio->evt_low_high |= BIT(data->hwirq);
                gpio->evt_lvl_edge |= BIT(data->hwirq);
                break;
        case IRQ_TYPE_EDGE_FALLING:
                gpio->evt_low_high &= ~BIT(data->hwirq);
                gpio->evt_lvl_edge |= BIT(data->hwirq);
                break;
        case IRQ_TYPE_LEVEL_HIGH:
                gpio->evt_low_high |= BIT(data->hwirq);
                gpio->evt_lvl_edge &= ~BIT(data->hwirq);
                break;
        case IRQ_TYPE_LEVEL_LOW:
                gpio->evt_low_high &= ~BIT(data->hwirq);
                gpio->evt_lvl_edge &= ~BIT(data->hwirq);
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static void kempld_irq_bus_lock(struct irq_data *data)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);

        mutex_lock(&gpio->irq_lock);
}

static void kempld_irq_bus_sync_unlock(struct irq_data *data)
{
        struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
        struct kempld_gpio_data *gpio = gpiochip_get_data(chip);
        struct kempld_device_data *pld = gpio->pld;

        kempld_get_mutex(pld);
        kempld_write16(pld, KEMPLD_GPIO_EVT_LVL_EDGE, gpio->evt_lvl_edge);
        kempld_write16(pld, KEMPLD_GPIO_EVT_LOW_HIGH, gpio->evt_low_high);
        kempld_write16(pld, KEMPLD_GPIO_IEN, gpio->ien);
        kempld_release_mutex(pld);

        mutex_unlock(&gpio->irq_lock);
}

static const struct irq_chip kempld_irqchip = {
        .name                   = "kempld-gpio",
        .irq_mask               = kempld_irq_mask,
        .irq_unmask             = kempld_irq_unmask,
        .irq_set_type           = kempld_irq_set_type,
        .irq_bus_lock           = kempld_irq_bus_lock,
        .irq_bus_sync_unlock    = kempld_irq_bus_sync_unlock,
        .flags                  = IRQCHIP_IMMUTABLE,
        GPIOCHIP_IRQ_RESOURCE_HELPERS,
};

static irqreturn_t kempld_gpio_irq_handler(int irq, void *data)
{
        struct kempld_gpio_data *gpio = data;
        struct gpio_chip *chip = &gpio->chip;
        unsigned int pin, child_irq;
        unsigned long status;

        kempld_get_mutex(gpio->pld);

        status = kempld_read16(gpio->pld, KEMPLD_GPIO_STS);
        if (status)
                kempld_write16(gpio->pld, KEMPLD_GPIO_STS, status);

        kempld_release_mutex(gpio->pld);

        status &= gpio->ien;
        if (!status)
                return IRQ_NONE;

        for_each_set_bit(pin, &status, chip->ngpio) {
                child_irq = irq_find_mapping(chip->irq.domain, pin);
                handle_nested_irq(child_irq);
        }

        return IRQ_HANDLED;
}

static int kempld_gpio_irq_init(struct device *dev,
                                struct kempld_gpio_data *gpio)
{
        struct kempld_device_data *pld = gpio->pld;
        struct gpio_chip *chip = &gpio->chip;
        struct gpio_irq_chip *girq;
        unsigned int irq;
        int ret;

        /* Get the IRQ configured by the BIOS in the PLD */
        kempld_get_mutex(pld);
        irq = kempld_read8(pld, KEMPLD_IRQ_GPIO);
        kempld_release_mutex(pld);

        if (irq == 0xff) {
                dev_info(dev, "GPIO controller has no IRQ support\n");
                return 0;
        }

        /* Allow overriding the IRQ with the module parameter */
        if (gpio_irq > 0) {
                dev_warn(dev, "Forcing IRQ to %d\n", gpio_irq);
                irq &= ~KEMPLD_IRQ_GPIO_MASK;
                irq |= gpio_irq & KEMPLD_IRQ_GPIO_MASK;
        }

        if (!(irq & KEMPLD_IRQ_GPIO_MASK)) {
                dev_warn(dev, "No IRQ configured\n");
                return 0;
        }

        /* Get the current config, disable all child interrupts, clear them
         * and set the parent IRQ
         */
        kempld_get_mutex(pld);
        gpio->evt_low_high = kempld_read16(pld, KEMPLD_GPIO_EVT_LOW_HIGH);
        gpio->evt_lvl_edge = kempld_read16(pld, KEMPLD_GPIO_EVT_LVL_EDGE);
        kempld_write16(pld, KEMPLD_GPIO_IEN, 0);
        kempld_write16(pld, KEMPLD_GPIO_STS, 0xFFFF);
        kempld_write16(pld, KEMPLD_IRQ_GPIO, irq);
        kempld_release_mutex(pld);

        girq = &chip->irq;
        gpio_irq_chip_set_chip(girq, &kempld_irqchip);

        girq->parent_handler = NULL;
        girq->num_parents = 0;
        girq->parents = NULL;
        girq->default_type = IRQ_TYPE_NONE;
        girq->handler = handle_simple_irq;
        girq->threaded = true;

        mutex_init(&gpio->irq_lock);

        ret = devm_request_threaded_irq(dev, irq & KEMPLD_IRQ_GPIO_MASK,
                                        NULL, kempld_gpio_irq_handler,
                                        IRQF_ONESHOT, chip->label,
                                        gpio);
        if (ret) {
                dev_err(dev, "failed to request irq %d\n", irq);
                return ret;
        }

        return 0;
}

static int kempld_gpio_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct kempld_device_data *pld = dev_get_drvdata(dev->parent);
        struct kempld_platform_data *pdata = dev_get_platdata(pld->dev);
        struct kempld_gpio_data *gpio;
        struct gpio_chip *chip;
        int ret;

        if (pld->info.spec_major < 2) {
                dev_err(dev,
                        "Driver only supports GPIO devices compatible to PLD spec. rev. 2.0 or higher\n");
                return -ENODEV;
        }

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

        /* Starting with version 2.8 there is a dedicated register for the
         * output state, earlier versions share the register used to read
         * the line level.
         */
        if (pld->info.spec_major > 2 || pld->info.spec_minor >= 8)
                gpio->out_lvl_reg = KEMPLD_GPIO_OUT_LVL;
        else
                gpio->out_lvl_reg = KEMPLD_GPIO_LVL;

        gpio->pld = pld;

        platform_set_drvdata(pdev, gpio);

        chip = &gpio->chip;
        chip->label = "gpio-kempld";
        chip->owner = THIS_MODULE;
        chip->parent = dev;
        chip->can_sleep = true;
        if (pdata && pdata->gpio_base)
                chip->base = pdata->gpio_base;
        else
                chip->base = -1;
        chip->direction_input = kempld_gpio_direction_input;
        chip->direction_output = kempld_gpio_direction_output;
        chip->get_direction = kempld_gpio_get_direction;
        chip->get = kempld_gpio_get;
        chip->get_multiple = kempld_gpio_get_multiple;
        chip->set = kempld_gpio_set;
        chip->set_multiple = kempld_gpio_set_multiple;
        chip->ngpio = kempld_gpio_pincount(pld);
        if (chip->ngpio == 0) {
                dev_err(dev, "No GPIO pins detected\n");
                return -ENODEV;
        }

        ret = kempld_gpio_irq_init(dev, gpio);
        if (ret)
                return ret;

        ret = devm_gpiochip_add_data(dev, chip, gpio);
        if (ret) {
                dev_err(dev, "Could not register GPIO chip\n");
                return ret;
        }

        dev_info(dev, "GPIO functionality initialized with %d pins\n",
                 chip->ngpio);

        return 0;
}

static struct platform_driver kempld_gpio_driver = {
        .driver = {
                .name = "kempld-gpio",
        },
        .probe          = kempld_gpio_probe,
};

module_platform_driver(kempld_gpio_driver);

MODULE_DESCRIPTION("KEM PLD GPIO Driver");
MODULE_AUTHOR("Michael Brunner <michael.brunner@kontron.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:kempld-gpio");