// 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/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_NUM(x)          (0x40 + (x) / 8)
#define KEMPLD_GPIO_LVL_NUM(x)          (0x42 + (x) / 8)
#define KEMPLD_GPIO_EVT_LVL_EDGE        0x46
#define KEMPLD_GPIO_IEN                 0x4A

struct kempld_gpio_data {
        struct gpio_chip                chip;
        struct kempld_device_data       *pld;
};

/*
 * 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, u8 bit, u8 val)
{
        u8 status;

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

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

        kempld_get_mutex(pld);
        status = kempld_read8(pld, reg);
        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_NUM(offset), offset);
}

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, KEMPLD_GPIO_LVL_NUM(offset), offset, value);
        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_NUM(offset), 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, KEMPLD_GPIO_LVL_NUM(offset), offset, value);
        kempld_gpio_bitop(pld, KEMPLD_GPIO_DIR_NUM(offset), 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_NUM(offset), 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 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;

        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->set = kempld_gpio_set;
        chip->ngpio = kempld_gpio_pincount(pld);
        if (chip->ngpio == 0) {
                dev_err(dev, "No GPIO pins detected\n");
                return -ENODEV;
        }

        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");