// SPDX-License-Identifier: GPL-2.0
//
// IXP4 GPIO driver
// Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org>
//
// based on previous work and know-how from:
// Deepak Saxena <dsaxena@plexity.net>

#include <linux/gpio/driver.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/irqchip.h>
#include <linux/of_irq.h>
#include <linux/platform_device.h>
#include <linux/bitops.h>

#define IXP4XX_REG_GPOUT	0x00
#define IXP4XX_REG_GPOE		0x04
#define IXP4XX_REG_GPIN		0x08
#define IXP4XX_REG_GPIS		0x0C
#define IXP4XX_REG_GPIT1	0x10
#define IXP4XX_REG_GPIT2	0x14
#define IXP4XX_REG_GPCLK	0x18
#define IXP4XX_REG_GPDBSEL	0x1C

/*
 * The hardware uses 3 bits to indicate interrupt "style".
 * we clear and set these three bits accordingly. The lower 24
 * bits in two registers (GPIT1 and GPIT2) are used to set up
 * the style for 8 lines each for a total of 16 GPIO lines.
 */
#define IXP4XX_GPIO_STYLE_ACTIVE_HIGH	0x0
#define IXP4XX_GPIO_STYLE_ACTIVE_LOW	0x1
#define IXP4XX_GPIO_STYLE_RISING_EDGE	0x2
#define IXP4XX_GPIO_STYLE_FALLING_EDGE	0x3
#define IXP4XX_GPIO_STYLE_TRANSITIONAL	0x4
#define IXP4XX_GPIO_STYLE_MASK		GENMASK(2, 0)
#define IXP4XX_GPIO_STYLE_SIZE		3

/**
 * struct ixp4xx_gpio - IXP4 GPIO state container
 * @dev: containing device for this instance
 * @fwnode: the fwnode for this GPIO chip
 * @gc: gpiochip for this instance
 * @base: remapped I/O-memory base
 * @irq_edge: Each bit represents an IRQ: 1: edge-triggered,
 * 0: level triggered
 */
struct ixp4xx_gpio {
	struct device *dev;
	struct fwnode_handle *fwnode;
	struct gpio_chip gc;
	void __iomem *base;
	unsigned long long irq_edge;
};

static void ixp4xx_gpio_irq_ack(struct irq_data *d)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
	struct ixp4xx_gpio *g = gpiochip_get_data(gc);

	__raw_writel(BIT(d->hwirq), g->base + IXP4XX_REG_GPIS);
}

static void ixp4xx_gpio_mask_irq(struct irq_data *d)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);

	irq_chip_mask_parent(d);
	gpiochip_disable_irq(gc, d->hwirq);
}

static void ixp4xx_gpio_irq_unmask(struct irq_data *d)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
	struct ixp4xx_gpio *g = gpiochip_get_data(gc);

	/* ACK when unmasking if not edge-triggered */
	if (!(g->irq_edge & BIT(d->hwirq)))
		ixp4xx_gpio_irq_ack(d);

	gpiochip_enable_irq(gc, d->hwirq);
	irq_chip_unmask_parent(d);
}

static int ixp4xx_gpio_irq_set_type(struct irq_data *d, unsigned int type)
{
	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
	struct ixp4xx_gpio *g = gpiochip_get_data(gc);
	int line = d->hwirq;
	unsigned long flags;
	u32 int_style;
	u32 int_reg;
	u32 val;

	switch (type) {
	case IRQ_TYPE_EDGE_BOTH:
		irq_set_handler_locked(d, handle_edge_irq);
		int_style = IXP4XX_GPIO_STYLE_TRANSITIONAL;
		g->irq_edge |= BIT(d->hwirq);
		break;
	case IRQ_TYPE_EDGE_RISING:
		irq_set_handler_locked(d, handle_edge_irq);
		int_style = IXP4XX_GPIO_STYLE_RISING_EDGE;
		g->irq_edge |= BIT(d->hwirq);
		break;
	case IRQ_TYPE_EDGE_FALLING:
		irq_set_handler_locked(d, handle_edge_irq);
		int_style = IXP4XX_GPIO_STYLE_FALLING_EDGE;
		g->irq_edge |= BIT(d->hwirq);
		break;
	case IRQ_TYPE_LEVEL_HIGH:
		irq_set_handler_locked(d, handle_level_irq);
		int_style = IXP4XX_GPIO_STYLE_ACTIVE_HIGH;
		g->irq_edge &= ~BIT(d->hwirq);
		break;
	case IRQ_TYPE_LEVEL_LOW:
		irq_set_handler_locked(d, handle_level_irq);
		int_style = IXP4XX_GPIO_STYLE_ACTIVE_LOW;
		g->irq_edge &= ~BIT(d->hwirq);
		break;
	default:
		return -EINVAL;
	}

	if (line >= 8) {
		/* pins 8-15 */
		line -= 8;
		int_reg = IXP4XX_REG_GPIT2;
	} else {
		/* pins 0-7 */
		int_reg = IXP4XX_REG_GPIT1;
	}

	raw_spin_lock_irqsave(&g->gc.bgpio_lock, flags);

	/* Clear the style for the appropriate pin */
	val = __raw_readl(g->base + int_reg);
	val &= ~(IXP4XX_GPIO_STYLE_MASK << (line * IXP4XX_GPIO_STYLE_SIZE));
	__raw_writel(val, g->base + int_reg);

	__raw_writel(BIT(line), g->base + IXP4XX_REG_GPIS);

	/* Set the new style */
	val = __raw_readl(g->base + int_reg);
	val |= (int_style << (line * IXP4XX_GPIO_STYLE_SIZE));
	__raw_writel(val, g->base + int_reg);

	/* Force-configure this line as an input */
	val = __raw_readl(g->base + IXP4XX_REG_GPOE);
	val |= BIT(d->hwirq);
	__raw_writel(val, g->base + IXP4XX_REG_GPOE);

	raw_spin_unlock_irqrestore(&g->gc.bgpio_lock, flags);

	/* This parent only accept level high (asserted) */
	return irq_chip_set_type_parent(d, IRQ_TYPE_LEVEL_HIGH);
}

static const struct irq_chip ixp4xx_gpio_irqchip = {
	.name = "IXP4GPIO",
	.irq_ack = ixp4xx_gpio_irq_ack,
	.irq_mask = ixp4xx_gpio_mask_irq,
	.irq_unmask = ixp4xx_gpio_irq_unmask,
	.irq_set_type = ixp4xx_gpio_irq_set_type,
	.flags = IRQCHIP_IMMUTABLE,
	GPIOCHIP_IRQ_RESOURCE_HELPERS,
};

static int ixp4xx_gpio_child_to_parent_hwirq(struct gpio_chip *gc,
					     unsigned int child,
					     unsigned int child_type,
					     unsigned int *parent,
					     unsigned int *parent_type)
{
	/* All these interrupts are level high in the CPU */
	*parent_type = IRQ_TYPE_LEVEL_HIGH;

	/* GPIO lines 0..12 have dedicated IRQs */
	if (child == 0) {
		*parent = 6;
		return 0;
	}
	if (child == 1) {
		*parent = 7;
		return 0;
	}
	if (child >= 2 && child <= 12) {
		*parent = child + 17;
		return 0;
	}
	return -EINVAL;
}

static int ixp4xx_gpio_probe(struct platform_device *pdev)
{
	unsigned long flags;
	struct device *dev = &pdev->dev;
	struct device_node *np = dev->of_node;
	struct irq_domain *parent;
	struct resource *res;
	struct ixp4xx_gpio *g;
	struct gpio_irq_chip *girq;
	struct device_node *irq_parent;
	int ret;

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

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	g->base = devm_ioremap_resource(dev, res);
	if (IS_ERR(g->base))
		return PTR_ERR(g->base);

	irq_parent = of_irq_find_parent(np);
	if (!irq_parent) {
		dev_err(dev, "no IRQ parent node\n");
		return -ENODEV;
	}
	parent = irq_find_host(irq_parent);
	if (!parent) {
		dev_err(dev, "no IRQ parent domain\n");
		return -ENODEV;
	}
	g->fwnode = of_node_to_fwnode(np);

	/*
	 * Make sure GPIO 14 and 15 are NOT used as clocks but GPIO on
	 * specific machines.
	 */
	if (of_machine_is_compatible("dlink,dsm-g600-a") ||
	    of_machine_is_compatible("iom,nas-100d"))
		__raw_writel(0x0, g->base + IXP4XX_REG_GPCLK);

	/*
	 * This is a very special big-endian ARM issue: when the IXP4xx is
	 * run in big endian mode, all registers in the machine are switched
	 * around to the CPU-native endianness. As you see mostly in the
	 * driver we use __raw_readl()/__raw_writel() to access the registers
	 * in the appropriate order. With the GPIO library we need to specify
	 * byte order explicitly, so this flag needs to be set when compiling
	 * for big endian.
	 */
#if defined(CONFIG_CPU_BIG_ENDIAN)
	flags = BGPIOF_BIG_ENDIAN_BYTE_ORDER;
#else
	flags = 0;
#endif

	/* Populate and register gpio chip */
	ret = bgpio_init(&g->gc, dev, 4,
			 g->base + IXP4XX_REG_GPIN,
			 g->base + IXP4XX_REG_GPOUT,
			 NULL,
			 NULL,
			 g->base + IXP4XX_REG_GPOE,
			 flags);
	if (ret) {
		dev_err(dev, "unable to init generic GPIO\n");
		return ret;
	}
	g->gc.ngpio = 16;
	g->gc.label = "IXP4XX_GPIO_CHIP";
	/*
	 * TODO: when we have migrated to device tree and all GPIOs
	 * are fetched using phandles, set this to -1 to get rid of
	 * the fixed gpiochip base.
	 */
	g->gc.base = 0;
	g->gc.parent = &pdev->dev;
	g->gc.owner = THIS_MODULE;

	girq = &g->gc.irq;
	gpio_irq_chip_set_chip(girq, &ixp4xx_gpio_irqchip);
	girq->fwnode = g->fwnode;
	girq->parent_domain = parent;
	girq->child_to_parent_hwirq = ixp4xx_gpio_child_to_parent_hwirq;
	girq->handler = handle_bad_irq;
	girq->default_type = IRQ_TYPE_NONE;

	ret = devm_gpiochip_add_data(dev, &g->gc, g);
	if (ret) {
		dev_err(dev, "failed to add SoC gpiochip\n");
		return ret;
	}

	platform_set_drvdata(pdev, g);
	dev_info(dev, "IXP4 GPIO registered\n");

	return 0;
}

static const struct of_device_id ixp4xx_gpio_of_match[] = {
	{
		.compatible = "intel,ixp4xx-gpio",
	},
	{},
};


static struct platform_driver ixp4xx_gpio_driver = {
	.driver = {
		.name		= "ixp4xx-gpio",
		.of_match_table = of_match_ptr(ixp4xx_gpio_of_match),
	},
	.probe = ixp4xx_gpio_probe,
};
builtin_platform_driver(ixp4xx_gpio_driver);