/*
 * Driver for Aeroflex Gaisler GRGPIO General Purpose I/O cores.
 *
 * 2013 (c) Aeroflex Gaisler AB
 *
 * This driver supports the GRGPIO GPIO core available in the GRLIB VHDL
 * IP core library.
 *
 * Full documentation of the GRGPIO core can be found here:
 * http://www.gaisler.com/products/grlib/grip.pdf
 *
 * See "Documentation/devicetree/bindings/gpio/gpio-grgpio.txt" for
 * information on open firmware properties.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * Contributors: Andreas Larsson <andreas@gaisler.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/gpio/driver.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/gpio/driver.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/bitops.h>

#define GRGPIO_MAX_NGPIO 32

#define GRGPIO_DATA             0x00
#define GRGPIO_OUTPUT           0x04
#define GRGPIO_DIR              0x08
#define GRGPIO_IMASK            0x0c
#define GRGPIO_IPOL             0x10
#define GRGPIO_IEDGE            0x14
#define GRGPIO_BYPASS           0x18
#define GRGPIO_IMAP_BASE        0x20

/* Structure for an irq of the core - called an underlying irq */
struct grgpio_uirq {
        u8 refcnt; /* Reference counter to manage requesting/freeing of uirq */
        u8 uirq; /* Underlying irq of the gpio driver */
};

/*
 * Structure for an irq of a gpio line handed out by this driver. The index is
 * used to map to the corresponding underlying irq.
 */
struct grgpio_lirq {
        s8 index; /* Index into struct grgpio_priv's uirqs, or -1 */
        u8 irq; /* irq for the gpio line */
};

struct grgpio_priv {
        struct gpio_chip gc;
        void __iomem *regs;
        struct device *dev;

        u32 imask; /* irq mask shadow register */

        /*
         * The grgpio core can have multiple "underlying" irqs. The gpio lines
         * can be mapped to any one or none of these underlying irqs
         * independently of each other. This driver sets up an irq domain and
         * hands out separate irqs to each gpio line
         */
        struct irq_domain *domain;

        /*
         * This array contains information on each underlying irq, each
         * irq of the grgpio core itself.
         */
        struct grgpio_uirq uirqs[GRGPIO_MAX_NGPIO];

        /*
         * This array contains information for each gpio line on the irqs
         * obtains from this driver. An index value of -1 for a certain gpio
         * line indicates that the line has no irq. Otherwise the index connects
         * the irq to the underlying irq by pointing into the uirqs array.
         */
        struct grgpio_lirq lirqs[GRGPIO_MAX_NGPIO];
};

static void grgpio_set_imask(struct grgpio_priv *priv, unsigned int offset,
                             int val)
{
        struct gpio_chip *gc = &priv->gc;

        if (val)
                priv->imask |= BIT(offset);
        else
                priv->imask &= ~BIT(offset);
        gc->write_reg(priv->regs + GRGPIO_IMASK, priv->imask);
}

static int grgpio_to_irq(struct gpio_chip *gc, unsigned offset)
{
        struct grgpio_priv *priv = gpiochip_get_data(gc);

        if (offset >= gc->ngpio)
                return -ENXIO;

        if (priv->lirqs[offset].index < 0)
                return -ENXIO;

        return irq_create_mapping(priv->domain, offset);
}

/* -------------------- IRQ chip functions -------------------- */

static int grgpio_irq_set_type(struct irq_data *d, unsigned int type)
{
        struct grgpio_priv *priv = irq_data_get_irq_chip_data(d);
        unsigned long flags;
        u32 mask = BIT(d->hwirq);
        u32 ipol;
        u32 iedge;
        u32 pol;
        u32 edge;

        switch (type) {
        case IRQ_TYPE_LEVEL_LOW:
                pol = 0;
                edge = 0;
                break;
        case IRQ_TYPE_LEVEL_HIGH:
                pol = mask;
                edge = 0;
                break;
        case IRQ_TYPE_EDGE_FALLING:
                pol = 0;
                edge = mask;
                break;
        case IRQ_TYPE_EDGE_RISING:
                pol = mask;
                edge = mask;
                break;
        default:
                return -EINVAL;
        }

        spin_lock_irqsave(&priv->gc.bgpio_lock, flags);

        ipol = priv->gc.read_reg(priv->regs + GRGPIO_IPOL) & ~mask;
        iedge = priv->gc.read_reg(priv->regs + GRGPIO_IEDGE) & ~mask;

        priv->gc.write_reg(priv->regs + GRGPIO_IPOL, ipol | pol);
        priv->gc.write_reg(priv->regs + GRGPIO_IEDGE, iedge | edge);

        spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);

        return 0;
}

static void grgpio_irq_mask(struct irq_data *d)
{
        struct grgpio_priv *priv = irq_data_get_irq_chip_data(d);
        int offset = d->hwirq;
        unsigned long flags;

        spin_lock_irqsave(&priv->gc.bgpio_lock, flags);

        grgpio_set_imask(priv, offset, 0);

        spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
}

static void grgpio_irq_unmask(struct irq_data *d)
{
        struct grgpio_priv *priv = irq_data_get_irq_chip_data(d);
        int offset = d->hwirq;
        unsigned long flags;

        spin_lock_irqsave(&priv->gc.bgpio_lock, flags);

        grgpio_set_imask(priv, offset, 1);

        spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
}

static struct irq_chip grgpio_irq_chip = {
        .name                   = "grgpio",
        .irq_mask               = grgpio_irq_mask,
        .irq_unmask             = grgpio_irq_unmask,
        .irq_set_type           = grgpio_irq_set_type,
};

static irqreturn_t grgpio_irq_handler(int irq, void *dev)
{
        struct grgpio_priv *priv = dev;
        int ngpio = priv->gc.ngpio;
        unsigned long flags;
        int i;
        int match = 0;

        spin_lock_irqsave(&priv->gc.bgpio_lock, flags);

        /*
         * For each gpio line, call its interrupt handler if it its underlying
         * irq matches the current irq that is handled.
         */
        for (i = 0; i < ngpio; i++) {
                struct grgpio_lirq *lirq = &priv->lirqs[i];

                if (priv->imask & BIT(i) && lirq->index >= 0 &&
                    priv->uirqs[lirq->index].uirq == irq) {
                        generic_handle_irq(lirq->irq);
                        match = 1;
                }
        }

        spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);

        if (!match)
                dev_warn(priv->dev, "No gpio line matched irq %d\n", irq);

        return IRQ_HANDLED;
}

/*
 * This function will be called as a consequence of the call to
 * irq_create_mapping in grgpio_to_irq
 */
static int grgpio_irq_map(struct irq_domain *d, unsigned int irq,
                          irq_hw_number_t hwirq)
{
        struct grgpio_priv *priv = d->host_data;
        struct grgpio_lirq *lirq;
        struct grgpio_uirq *uirq;
        unsigned long flags;
        int offset = hwirq;
        int ret = 0;

        if (!priv)
                return -EINVAL;

        lirq = &priv->lirqs[offset];
        if (lirq->index < 0)
                return -EINVAL;

        dev_dbg(priv->dev, "Mapping irq %d for gpio line %d\n",
                irq, offset);

        spin_lock_irqsave(&priv->gc.bgpio_lock, flags);

        /* Request underlying irq if not already requested */
        lirq->irq = irq;
        uirq = &priv->uirqs[lirq->index];
        if (uirq->refcnt == 0) {
                ret = request_irq(uirq->uirq, grgpio_irq_handler, 0,
                                  dev_name(priv->dev), priv);
                if (ret) {
                        dev_err(priv->dev,
                                "Could not request underlying irq %d\n",
                                uirq->uirq);

                        spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);

                        return ret;
                }
        }
        uirq->refcnt++;

        spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);

        /* Setup irq  */
        irq_set_chip_data(irq, priv);
        irq_set_chip_and_handler(irq, &grgpio_irq_chip,
                                 handle_simple_irq);
        irq_set_noprobe(irq);

        return ret;
}

static void grgpio_irq_unmap(struct irq_domain *d, unsigned int irq)
{
        struct grgpio_priv *priv = d->host_data;
        int index;
        struct grgpio_lirq *lirq;
        struct grgpio_uirq *uirq;
        unsigned long flags;
        int ngpio = priv->gc.ngpio;
        int i;

        irq_set_chip_and_handler(irq, NULL, NULL);
        irq_set_chip_data(irq, NULL);

        spin_lock_irqsave(&priv->gc.bgpio_lock, flags);

        /* Free underlying irq if last user unmapped */
        index = -1;
        for (i = 0; i < ngpio; i++) {
                lirq = &priv->lirqs[i];
                if (lirq->irq == irq) {
                        grgpio_set_imask(priv, i, 0);
                        lirq->irq = 0;
                        index = lirq->index;
                        break;
                }
        }
        WARN_ON(index < 0);

        if (index >= 0) {
                uirq = &priv->uirqs[lirq->index];
                uirq->refcnt--;
                if (uirq->refcnt == 0)
                        free_irq(uirq->uirq, priv);
        }

        spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
}

static const struct irq_domain_ops grgpio_irq_domain_ops = {
        .map    = grgpio_irq_map,
        .unmap  = grgpio_irq_unmap,
};

/* ------------------------------------------------------------ */

static int grgpio_probe(struct platform_device *ofdev)
{
        struct device_node *np = ofdev->dev.of_node;
        void  __iomem *regs;
        struct gpio_chip *gc;
        struct grgpio_priv *priv;
        struct resource *res;
        int err;
        u32 prop;
        s32 *irqmap;
        int size;
        int i;

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

        res = platform_get_resource(ofdev, IORESOURCE_MEM, 0);
        regs = devm_ioremap_resource(&ofdev->dev, res);
        if (IS_ERR(regs))
                return PTR_ERR(regs);

        gc = &priv->gc;
        err = bgpio_init(gc, &ofdev->dev, 4, regs + GRGPIO_DATA,
                         regs + GRGPIO_OUTPUT, NULL, regs + GRGPIO_DIR, NULL,
                         BGPIOF_BIG_ENDIAN_BYTE_ORDER);
        if (err) {
                dev_err(&ofdev->dev, "bgpio_init() failed\n");
                return err;
        }

        priv->regs = regs;
        priv->imask = gc->read_reg(regs + GRGPIO_IMASK);
        priv->dev = &ofdev->dev;

        gc->of_node = np;
        gc->owner = THIS_MODULE;
        gc->to_irq = grgpio_to_irq;
        gc->label = devm_kasprintf(&ofdev->dev, GFP_KERNEL, "%pOF", np);
        gc->base = -1;

        err = of_property_read_u32(np, "nbits", &prop);
        if (err || prop <= 0 || prop > GRGPIO_MAX_NGPIO) {
                gc->ngpio = GRGPIO_MAX_NGPIO;
                dev_dbg(&ofdev->dev,
                        "No or invalid nbits property: assume %d\n", gc->ngpio);
        } else {
                gc->ngpio = prop;
        }

        /*
         * The irqmap contains the index values indicating which underlying irq,
         * if anyone, is connected to that line
         */
        irqmap = (s32 *)of_get_property(np, "irqmap", &size);
        if (irqmap) {
                if (size < gc->ngpio) {
                        dev_err(&ofdev->dev,
                                "irqmap shorter than ngpio (%d < %d)\n",
                                size, gc->ngpio);
                        return -EINVAL;
                }

                priv->domain = irq_domain_add_linear(np, gc->ngpio,
                                                     &grgpio_irq_domain_ops,
                                                     priv);
                if (!priv->domain) {
                        dev_err(&ofdev->dev, "Could not add irq domain\n");
                        return -EINVAL;
                }

                for (i = 0; i < gc->ngpio; i++) {
                        struct grgpio_lirq *lirq;
                        int ret;

                        lirq = &priv->lirqs[i];
                        lirq->index = irqmap[i];

                        if (lirq->index < 0)
                                continue;

                        ret = platform_get_irq(ofdev, lirq->index);
                        if (ret <= 0) {
                                /*
                                 * Continue without irq functionality for that
                                 * gpio line
                                 */
                                dev_err(priv->dev,
                                        "Failed to get irq for offset %d\n", i);
                                continue;
                        }
                        priv->uirqs[lirq->index].uirq = ret;
                }
        }

        platform_set_drvdata(ofdev, priv);

        err = gpiochip_add_data(gc, priv);
        if (err) {
                dev_err(&ofdev->dev, "Could not add gpiochip\n");
                if (priv->domain)
                        irq_domain_remove(priv->domain);
                return err;
        }

        dev_info(&ofdev->dev, "regs=0x%p, base=%d, ngpio=%d, irqs=%s\n",
                 priv->regs, gc->base, gc->ngpio, priv->domain ? "on" : "off");

        return 0;
}

static int grgpio_remove(struct platform_device *ofdev)
{
        struct grgpio_priv *priv = platform_get_drvdata(ofdev);
        unsigned long flags;
        int i;
        int ret = 0;

        spin_lock_irqsave(&priv->gc.bgpio_lock, flags);

        if (priv->domain) {
                for (i = 0; i < GRGPIO_MAX_NGPIO; i++) {
                        if (priv->uirqs[i].refcnt != 0) {
                                ret = -EBUSY;
                                goto out;
                        }
                }
        }

        gpiochip_remove(&priv->gc);

        if (priv->domain)
                irq_domain_remove(priv->domain);

out:
        spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);

        return ret;
}

static const struct of_device_id grgpio_match[] = {
        {.name = "GAISLER_GPIO"},
        {.name = "01_01a"},
        {},
};

MODULE_DEVICE_TABLE(of, grgpio_match);

static struct platform_driver grgpio_driver = {
        .driver = {
                .name = "grgpio",
                .of_match_table = grgpio_match,
        },
        .probe = grgpio_probe,
        .remove = grgpio_remove,
};
module_platform_driver(grgpio_driver);

MODULE_AUTHOR("Aeroflex Gaisler AB.");
MODULE_DESCRIPTION("Driver for Aeroflex Gaisler GRGPIO");
MODULE_LICENSE("GPL");