// SPDX-License-Identifier: GPL-2.0-only
/*
 * GPIO driver for the ACCES 104-IDI-48 family
 * Copyright (C) 2015 William Breathitt Gray
 *
 * This driver supports the following ACCES devices: 104-IDI-48A,
 * 104-IDI-48AC, 104-IDI-48B, and 104-IDI-48BC.
 */
#include <linux/bits.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>
#include <linux/types.h>

#include "gpio-i8255.h"

MODULE_IMPORT_NS(I8255);

#define IDI_48_EXTENT 8
#define MAX_NUM_IDI_48 max_num_isa_dev(IDI_48_EXTENT)

static unsigned int base[MAX_NUM_IDI_48];
static unsigned int num_idi_48;
module_param_hw_array(base, uint, ioport, &num_idi_48, 0);
MODULE_PARM_DESC(base, "ACCES 104-IDI-48 base addresses");

static unsigned int irq[MAX_NUM_IDI_48];
static unsigned int num_irq;
module_param_hw_array(irq, uint, irq, &num_irq, 0);
MODULE_PARM_DESC(irq, "ACCES 104-IDI-48 interrupt line numbers");

/**
 * struct idi_48_reg - device register structure
 * @port0:	Port 0 Inputs
 * @unused:	Unused
 * @port1:	Port 1 Inputs
 * @irq:	Read: IRQ Status Register/IRQ Clear
 *		Write: IRQ Enable/Disable
 */
struct idi_48_reg {
	u8 port0[3];
	u8 unused;
	u8 port1[3];
	u8 irq;
};

/**
 * struct idi_48_gpio - GPIO device private data structure
 * @chip:	instance of the gpio_chip
 * @lock:	synchronization lock to prevent I/O race conditions
 * @irq_mask:	input bits affected by interrupts
 * @reg:	I/O address offset for the device registers
 * @cos_enb:	Change-Of-State IRQ enable boundaries mask
 */
struct idi_48_gpio {
	struct gpio_chip chip;
	spinlock_t lock;
	unsigned char irq_mask[6];
	struct idi_48_reg __iomem *reg;
	unsigned char cos_enb;
};

static int idi_48_gpio_get_direction(struct gpio_chip *chip, unsigned int offset)
{
	return GPIO_LINE_DIRECTION_IN;
}

static int idi_48_gpio_direction_input(struct gpio_chip *chip, unsigned int offset)
{
	return 0;
}

static int idi_48_gpio_get(struct gpio_chip *chip, unsigned int offset)
{
	struct idi_48_gpio *const idi48gpio = gpiochip_get_data(chip);
	void __iomem *const ppi = idi48gpio->reg;

	return i8255_get(ppi, offset);
}

static int idi_48_gpio_get_multiple(struct gpio_chip *chip, unsigned long *mask,
	unsigned long *bits)
{
	struct idi_48_gpio *const idi48gpio = gpiochip_get_data(chip);
	void __iomem *const ppi = idi48gpio->reg;

	i8255_get_multiple(ppi, mask, bits, chip->ngpio);

	return 0;
}

static void idi_48_irq_ack(struct irq_data *data)
{
}

static void idi_48_irq_mask(struct irq_data *data)
{
	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
	struct idi_48_gpio *const idi48gpio = gpiochip_get_data(chip);
	const unsigned int offset = irqd_to_hwirq(data);
	const unsigned long boundary = offset / 8;
	const unsigned long mask = BIT(offset % 8);
	unsigned long flags;

	spin_lock_irqsave(&idi48gpio->lock, flags);

	idi48gpio->irq_mask[boundary] &= ~mask;
	gpiochip_disable_irq(chip, offset);

	/* Exit early if there are still input lines with IRQ unmasked */
	if (idi48gpio->irq_mask[boundary])
		goto exit;

	idi48gpio->cos_enb &= ~BIT(boundary);

	iowrite8(idi48gpio->cos_enb, &idi48gpio->reg->irq);

exit:
	spin_unlock_irqrestore(&idi48gpio->lock, flags);
}

static void idi_48_irq_unmask(struct irq_data *data)
{
	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
	struct idi_48_gpio *const idi48gpio = gpiochip_get_data(chip);
	const unsigned int offset = irqd_to_hwirq(data);
	const unsigned long boundary = offset / 8;
	const unsigned long mask = BIT(offset % 8);
	unsigned int prev_irq_mask;
	unsigned long flags;

	spin_lock_irqsave(&idi48gpio->lock, flags);

	prev_irq_mask = idi48gpio->irq_mask[boundary];

	gpiochip_enable_irq(chip, offset);
	idi48gpio->irq_mask[boundary] |= mask;

	/* Exit early if IRQ was already unmasked for this boundary */
	if (prev_irq_mask)
		goto exit;

	idi48gpio->cos_enb |= BIT(boundary);

	iowrite8(idi48gpio->cos_enb, &idi48gpio->reg->irq);

exit:
	spin_unlock_irqrestore(&idi48gpio->lock, flags);
}

static int idi_48_irq_set_type(struct irq_data *data, unsigned int flow_type)
{
	/* The only valid irq types are none and both-edges */
	if (flow_type != IRQ_TYPE_NONE &&
		(flow_type & IRQ_TYPE_EDGE_BOTH) != IRQ_TYPE_EDGE_BOTH)
		return -EINVAL;

	return 0;
}

static const struct irq_chip idi_48_irqchip = {
	.name = "104-idi-48",
	.irq_ack = idi_48_irq_ack,
	.irq_mask = idi_48_irq_mask,
	.irq_unmask = idi_48_irq_unmask,
	.irq_set_type = idi_48_irq_set_type,
	.flags = IRQCHIP_IMMUTABLE,
	GPIOCHIP_IRQ_RESOURCE_HELPERS,
};

static irqreturn_t idi_48_irq_handler(int irq, void *dev_id)
{
	struct idi_48_gpio *const idi48gpio = dev_id;
	unsigned long cos_status;
	unsigned long boundary;
	unsigned long irq_mask;
	unsigned long bit_num;
	unsigned long gpio;
	struct gpio_chip *const chip = &idi48gpio->chip;

	spin_lock(&idi48gpio->lock);

	cos_status = ioread8(&idi48gpio->reg->irq);

	/* IRQ Status (bit 6) is active low (0 = IRQ generated by device) */
	if (cos_status & BIT(6)) {
		spin_unlock(&idi48gpio->lock);
		return IRQ_NONE;
	}

	/* Bit 0-5 indicate which Change-Of-State boundary triggered the IRQ */
	cos_status &= 0x3F;

	for_each_set_bit(boundary, &cos_status, 6) {
		irq_mask = idi48gpio->irq_mask[boundary];

		for_each_set_bit(bit_num, &irq_mask, 8) {
			gpio = bit_num + boundary * 8;

			generic_handle_domain_irq(chip->irq.domain,
						  gpio);
		}
	}

	spin_unlock(&idi48gpio->lock);

	return IRQ_HANDLED;
}

#define IDI48_NGPIO 48
static const char *idi48_names[IDI48_NGPIO] = {
	"Bit 0 A", "Bit 1 A", "Bit 2 A", "Bit 3 A", "Bit 4 A", "Bit 5 A",
	"Bit 6 A", "Bit 7 A", "Bit 8 A", "Bit 9 A", "Bit 10 A", "Bit 11 A",
	"Bit 12 A", "Bit 13 A", "Bit 14 A", "Bit 15 A",	"Bit 16 A", "Bit 17 A",
	"Bit 18 A", "Bit 19 A", "Bit 20 A", "Bit 21 A", "Bit 22 A", "Bit 23 A",
	"Bit 0 B", "Bit 1 B", "Bit 2 B", "Bit 3 B", "Bit 4 B", "Bit 5 B",
	"Bit 6 B", "Bit 7 B", "Bit 8 B", "Bit 9 B", "Bit 10 B", "Bit 11 B",
	"Bit 12 B", "Bit 13 B", "Bit 14 B", "Bit 15 B",	"Bit 16 B", "Bit 17 B",
	"Bit 18 B", "Bit 19 B", "Bit 20 B", "Bit 21 B", "Bit 22 B", "Bit 23 B"
};

static int idi_48_irq_init_hw(struct gpio_chip *gc)
{
	struct idi_48_gpio *const idi48gpio = gpiochip_get_data(gc);

	/* Disable IRQ by default */
	iowrite8(0, &idi48gpio->reg->irq);
	ioread8(&idi48gpio->reg->irq);

	return 0;
}

static int idi_48_probe(struct device *dev, unsigned int id)
{
	struct idi_48_gpio *idi48gpio;
	const char *const name = dev_name(dev);
	struct gpio_irq_chip *girq;
	int err;

	idi48gpio = devm_kzalloc(dev, sizeof(*idi48gpio), GFP_KERNEL);
	if (!idi48gpio)
		return -ENOMEM;

	if (!devm_request_region(dev, base[id], IDI_48_EXTENT, name)) {
		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
			base[id], base[id] + IDI_48_EXTENT);
		return -EBUSY;
	}

	idi48gpio->reg = devm_ioport_map(dev, base[id], IDI_48_EXTENT);
	if (!idi48gpio->reg)
		return -ENOMEM;

	idi48gpio->chip.label = name;
	idi48gpio->chip.parent = dev;
	idi48gpio->chip.owner = THIS_MODULE;
	idi48gpio->chip.base = -1;
	idi48gpio->chip.ngpio = IDI48_NGPIO;
	idi48gpio->chip.names = idi48_names;
	idi48gpio->chip.get_direction = idi_48_gpio_get_direction;
	idi48gpio->chip.direction_input = idi_48_gpio_direction_input;
	idi48gpio->chip.get = idi_48_gpio_get;
	idi48gpio->chip.get_multiple = idi_48_gpio_get_multiple;

	girq = &idi48gpio->chip.irq;
	gpio_irq_chip_set_chip(girq, &idi_48_irqchip);
	/* This will let us handle the parent IRQ in the driver */
	girq->parent_handler = NULL;
	girq->num_parents = 0;
	girq->parents = NULL;
	girq->default_type = IRQ_TYPE_NONE;
	girq->handler = handle_edge_irq;
	girq->init_hw = idi_48_irq_init_hw;

	spin_lock_init(&idi48gpio->lock);

	err = devm_gpiochip_add_data(dev, &idi48gpio->chip, idi48gpio);
	if (err) {
		dev_err(dev, "GPIO registering failed (%d)\n", err);
		return err;
	}

	err = devm_request_irq(dev, irq[id], idi_48_irq_handler, IRQF_SHARED,
		name, idi48gpio);
	if (err) {
		dev_err(dev, "IRQ handler registering failed (%d)\n", err);
		return err;
	}

	return 0;
}

static struct isa_driver idi_48_driver = {
	.probe = idi_48_probe,
	.driver = {
		.name = "104-idi-48"
	},
};
module_isa_driver_with_irq(idi_48_driver, num_idi_48, num_irq);

MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
MODULE_DESCRIPTION("ACCES 104-IDI-48 GPIO driver");
MODULE_LICENSE("GPL v2");