// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2019 Bootlin
 * Author: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
 */

#include <linux/err.h>
#include <linux/gpio/driver.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>
#include <linux/mfd/syscon.h>

#define LOGICVC_CTRL_REG                0x40
#define LOGICVC_CTRL_GPIO_SHIFT         11
#define LOGICVC_CTRL_GPIO_BITS          5

#define LOGICVC_POWER_CTRL_REG          0x78
#define LOGICVC_POWER_CTRL_GPIO_SHIFT   0
#define LOGICVC_POWER_CTRL_GPIO_BITS    4

struct logicvc_gpio {
        struct gpio_chip chip;
        struct regmap *regmap;
};

static void logicvc_gpio_offset(struct logicvc_gpio *logicvc, unsigned offset,
                                unsigned int *reg, unsigned int *bit)
{
        if (offset >= LOGICVC_CTRL_GPIO_BITS) {
                *reg = LOGICVC_POWER_CTRL_REG;

                /* To the (virtual) power ctrl offset. */
                offset -= LOGICVC_CTRL_GPIO_BITS;
                /* To the actual bit offset in reg. */
                offset += LOGICVC_POWER_CTRL_GPIO_SHIFT;
        } else {
                *reg = LOGICVC_CTRL_REG;

                /* To the actual bit offset in reg. */
                offset += LOGICVC_CTRL_GPIO_SHIFT;
        }

        *bit = BIT(offset);
}

static int logicvc_gpio_get(struct gpio_chip *chip, unsigned offset)
{
        struct logicvc_gpio *logicvc = gpiochip_get_data(chip);
        unsigned int reg, bit, value;
        int ret;

        logicvc_gpio_offset(logicvc, offset, &reg, &bit);

        ret = regmap_read(logicvc->regmap, reg, &value);
        if (ret)
                return ret;

        return !!(value & bit);
}

static int logicvc_gpio_set(struct gpio_chip *chip, unsigned int offset,
                            int value)
{
        struct logicvc_gpio *logicvc = gpiochip_get_data(chip);
        unsigned int reg, bit;

        logicvc_gpio_offset(logicvc, offset, &reg, &bit);

        return regmap_update_bits(logicvc->regmap, reg, bit, value ? bit : 0);
}

static int logicvc_gpio_direction_output(struct gpio_chip *chip,
                                         unsigned offset, int value)
{
        /* Pins are always configured as output, so just set the value. */
        return logicvc_gpio_set(chip, offset, value);
}

static struct regmap_config logicvc_gpio_regmap_config = {
        .reg_bits       = 32,
        .val_bits       = 32,
        .reg_stride     = 4,
        .name           = "logicvc-gpio",
};

static int logicvc_gpio_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct device_node *of_node = dev->of_node;
        struct logicvc_gpio *logicvc;
        int ret;

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

        /* Try to get regmap from parent first. */
        logicvc->regmap = syscon_node_to_regmap(of_node->parent);

        /* Grab our own regmap if that fails. */
        if (IS_ERR(logicvc->regmap)) {
                struct resource res;
                void __iomem *base;

                ret = of_address_to_resource(of_node, 0, &res);
                if (ret) {
                        dev_err(dev, "Failed to get resource from address\n");
                        return ret;
                }

                base = devm_ioremap_resource(dev, &res);
                if (IS_ERR(base))
                        return PTR_ERR(base);

                logicvc_gpio_regmap_config.max_register = resource_size(&res) -
                        logicvc_gpio_regmap_config.reg_stride;

                logicvc->regmap =
                        devm_regmap_init_mmio(dev, base,
                                              &logicvc_gpio_regmap_config);
                if (IS_ERR(logicvc->regmap)) {
                        dev_err(dev, "Failed to create regmap for I/O\n");
                        return PTR_ERR(logicvc->regmap);
                }
        }

        logicvc->chip.parent = dev;
        logicvc->chip.owner = THIS_MODULE;
        logicvc->chip.label = dev_name(dev);
        logicvc->chip.base = -1;
        logicvc->chip.ngpio = LOGICVC_CTRL_GPIO_BITS +
                              LOGICVC_POWER_CTRL_GPIO_BITS;
        logicvc->chip.get = logicvc_gpio_get;
        logicvc->chip.set = logicvc_gpio_set;
        logicvc->chip.direction_output = logicvc_gpio_direction_output;

        return devm_gpiochip_add_data(dev, &logicvc->chip, logicvc);
}

static const struct of_device_id logicivc_gpio_of_table[] = {
        {
                .compatible     = "xylon,logicvc-3.02.a-gpio",
        },
        { }
};

MODULE_DEVICE_TABLE(of, logicivc_gpio_of_table);

static struct platform_driver logicvc_gpio_driver = {
        .driver = {
                .name           = "gpio-logicvc",
                .of_match_table = logicivc_gpio_of_table,
        },
        .probe  = logicvc_gpio_probe,
};

module_platform_driver(logicvc_gpio_driver);

MODULE_AUTHOR("Paul Kocialkowski <paul.kocialkowski@bootlin.com>");
MODULE_DESCRIPTION("Xylon LogiCVC GPIO driver");
MODULE_LICENSE("GPL");