/*
 * Multiplexed-IRQs driver for TS-4800's FPGA
 *
 * Copyright (c) 2015 - Savoir-faire Linux
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/irqchip.h>
#include <linux/irqchip/chained_irq.h>
#include <linux/irqdomain.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/platform_device.h>
#include <linux/seq_file.h>

#define IRQ_MASK        0x4
#define IRQ_STATUS      0x8

struct ts4800_irq_data {
        void __iomem            *base;
        struct platform_device  *pdev;
        struct irq_domain       *domain;
        unsigned int            parent_irq;
};

static void ts4800_irq_mask(struct irq_data *d)
{
        struct ts4800_irq_data *data = irq_data_get_irq_chip_data(d);
        u16 reg = readw(data->base + IRQ_MASK);
        u16 mask = 1 << d->hwirq;

        writew(reg | mask, data->base + IRQ_MASK);
}

static void ts4800_irq_unmask(struct irq_data *d)
{
        struct ts4800_irq_data *data = irq_data_get_irq_chip_data(d);
        u16 reg = readw(data->base + IRQ_MASK);
        u16 mask = 1 << d->hwirq;

        writew(reg & ~mask, data->base + IRQ_MASK);
}

static void ts4800_irq_print_chip(struct irq_data *d, struct seq_file *p)
{
        struct ts4800_irq_data *data = irq_data_get_irq_chip_data(d);

        seq_puts(p, dev_name(&data->pdev->dev));
}

static const struct irq_chip ts4800_chip = {
        .irq_mask       = ts4800_irq_mask,
        .irq_unmask     = ts4800_irq_unmask,
        .irq_print_chip = ts4800_irq_print_chip,
};

static int ts4800_irqdomain_map(struct irq_domain *d, unsigned int irq,
                                irq_hw_number_t hwirq)
{
        struct ts4800_irq_data *data = d->host_data;

        irq_set_chip_and_handler(irq, &ts4800_chip, handle_simple_irq);
        irq_set_chip_data(irq, data);
        irq_set_noprobe(irq);

        return 0;
}

static const struct irq_domain_ops ts4800_ic_ops = {
        .map = ts4800_irqdomain_map,
        .xlate = irq_domain_xlate_onecell,
};

static void ts4800_ic_chained_handle_irq(struct irq_desc *desc)
{
        struct ts4800_irq_data *data = irq_desc_get_handler_data(desc);
        struct irq_chip *chip = irq_desc_get_chip(desc);
        u16 status = readw(data->base + IRQ_STATUS);

        chained_irq_enter(chip, desc);

        if (unlikely(status == 0)) {
                handle_bad_irq(desc);
                goto out;
        }

        do {
                unsigned int bit = __ffs(status);

                generic_handle_domain_irq(data->domain, bit);
                status &= ~(1 << bit);
        } while (status);

out:
        chained_irq_exit(chip, desc);
}

static int ts4800_ic_probe(struct platform_device *pdev)
{
        struct device_node *node = pdev->dev.of_node;
        struct ts4800_irq_data *data;
        int parent_irq;

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

        data->pdev = pdev;
        data->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(data->base))
                return PTR_ERR(data->base);

        writew(0xFFFF, data->base + IRQ_MASK);

        parent_irq = irq_of_parse_and_map(node, 0);
        if (!parent_irq) {
                dev_err(&pdev->dev, "failed to get parent IRQ\n");
                return -EINVAL;
        }

        data->domain = irq_domain_create_linear(dev_fwnode(&pdev->dev), 8, &ts4800_ic_ops, data);
        if (!data->domain) {
                dev_err(&pdev->dev, "cannot add IRQ domain\n");
                return -ENOMEM;
        }

        irq_set_chained_handler_and_data(parent_irq,
                                         ts4800_ic_chained_handle_irq, data);

        data->parent_irq = parent_irq;
        platform_set_drvdata(pdev, data);

        return 0;
}

static void ts4800_ic_remove(struct platform_device *pdev)
{
        struct ts4800_irq_data *data = platform_get_drvdata(pdev);
        unsigned int hwirq;

        irq_set_chained_handler_and_data(data->parent_irq, NULL, NULL);

        for (hwirq = 0; hwirq < 8; hwirq++)
                irq_dispose_mapping(irq_find_mapping(data->domain, hwirq));

        irq_dispose_mapping(data->parent_irq);

        irq_domain_remove(data->domain);
}

static const struct of_device_id ts4800_ic_of_match[] = {
        { .compatible = "technologic,ts4800-irqc", },
        {},
};
MODULE_DEVICE_TABLE(of, ts4800_ic_of_match);

static struct platform_driver ts4800_ic_driver = {
        .probe          = ts4800_ic_probe,
        .remove         = ts4800_ic_remove,
        .driver = {
                .name           = "ts4800-irqc",
                .of_match_table = ts4800_ic_of_match,
        },
};
module_platform_driver(ts4800_ic_driver);

MODULE_AUTHOR("Damien Riegel <damien.riegel@savoirfairelinux.com>");
MODULE_DESCRIPTION("Multiplexed-IRQs driver for TS-4800's FPGA");
MODULE_LICENSE("GPL v2");