/*
 * Renesas INTC External IRQ Pin Driver
 *
 *  Copyright (C) 2013 Magnus Damm
 *
 * 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
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/init.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/of_device.h>
#include <linux/pm_runtime.h>

#define INTC_IRQPIN_MAX 8 /* maximum 8 interrupts per driver instance */

#define INTC_IRQPIN_REG_SENSE 0 /* ICRn */
#define INTC_IRQPIN_REG_PRIO 1 /* INTPRInn */
#define INTC_IRQPIN_REG_SOURCE 2 /* INTREQnn */
#define INTC_IRQPIN_REG_MASK 3 /* INTMSKnn */
#define INTC_IRQPIN_REG_CLEAR 4 /* INTMSKCLRnn */
#define INTC_IRQPIN_REG_NR_MANDATORY 5
#define INTC_IRQPIN_REG_IRLM 5 /* ICR0 with IRLM bit (optional) */
#define INTC_IRQPIN_REG_NR 6

/* INTC external IRQ PIN hardware register access:
 *
 * SENSE is read-write 32-bit with 2-bits or 4-bits per IRQ (*)
 * PRIO is read-write 32-bit with 4-bits per IRQ (**)
 * SOURCE is read-only 32-bit or 8-bit with 1-bit per IRQ (***)
 * MASK is write-only 32-bit or 8-bit with 1-bit per IRQ (***)
 * CLEAR is write-only 32-bit or 8-bit with 1-bit per IRQ (***)
 *
 * (*) May be accessed by more than one driver instance - lock needed
 * (**) Read-modify-write access by one driver instance - lock needed
 * (***) Accessed by one driver instance only - no locking needed
 */

struct intc_irqpin_iomem {
        void __iomem *iomem;
        unsigned long (*read)(void __iomem *iomem);
        void (*write)(void __iomem *iomem, unsigned long data);
        int width;
};

struct intc_irqpin_irq {
        int hw_irq;
        int requested_irq;
        int domain_irq;
        struct intc_irqpin_priv *p;
};

struct intc_irqpin_priv {
        struct intc_irqpin_iomem iomem[INTC_IRQPIN_REG_NR];
        struct intc_irqpin_irq irq[INTC_IRQPIN_MAX];
        unsigned int sense_bitfield_width;
        struct platform_device *pdev;
        struct irq_chip irq_chip;
        struct irq_domain *irq_domain;
        atomic_t wakeup_path;
        unsigned shared_irqs:1;
        u8 shared_irq_mask;
};

struct intc_irqpin_config {
        unsigned int irlm_bit;
        unsigned needs_irlm:1;
};

static unsigned long intc_irqpin_read32(void __iomem *iomem)
{
        return ioread32(iomem);
}

static unsigned long intc_irqpin_read8(void __iomem *iomem)
{
        return ioread8(iomem);
}

static void intc_irqpin_write32(void __iomem *iomem, unsigned long data)
{
        iowrite32(data, iomem);
}

static void intc_irqpin_write8(void __iomem *iomem, unsigned long data)
{
        iowrite8(data, iomem);
}

static inline unsigned long intc_irqpin_read(struct intc_irqpin_priv *p,
                                             int reg)
{
        struct intc_irqpin_iomem *i = &p->iomem[reg];

        return i->read(i->iomem);
}

static inline void intc_irqpin_write(struct intc_irqpin_priv *p,
                                     int reg, unsigned long data)
{
        struct intc_irqpin_iomem *i = &p->iomem[reg];

        i->write(i->iomem, data);
}

static inline unsigned long intc_irqpin_hwirq_mask(struct intc_irqpin_priv *p,
                                                   int reg, int hw_irq)
{
        return BIT((p->iomem[reg].width - 1) - hw_irq);
}

static inline void intc_irqpin_irq_write_hwirq(struct intc_irqpin_priv *p,
                                               int reg, int hw_irq)
{
        intc_irqpin_write(p, reg, intc_irqpin_hwirq_mask(p, reg, hw_irq));
}

static DEFINE_RAW_SPINLOCK(intc_irqpin_lock); /* only used by slow path */

static void intc_irqpin_read_modify_write(struct intc_irqpin_priv *p,
                                          int reg, int shift,
                                          int width, int value)
{
        unsigned long flags;
        unsigned long tmp;

        raw_spin_lock_irqsave(&intc_irqpin_lock, flags);

        tmp = intc_irqpin_read(p, reg);
        tmp &= ~(((1 << width) - 1) << shift);
        tmp |= value << shift;
        intc_irqpin_write(p, reg, tmp);

        raw_spin_unlock_irqrestore(&intc_irqpin_lock, flags);
}

static void intc_irqpin_mask_unmask_prio(struct intc_irqpin_priv *p,
                                         int irq, int do_mask)
{
        /* The PRIO register is assumed to be 32-bit with fixed 4-bit fields. */
        int bitfield_width = 4;
        int shift = 32 - (irq + 1) * bitfield_width;

        intc_irqpin_read_modify_write(p, INTC_IRQPIN_REG_PRIO,
                                      shift, bitfield_width,
                                      do_mask ? 0 : (1 << bitfield_width) - 1);
}

static int intc_irqpin_set_sense(struct intc_irqpin_priv *p, int irq, int value)
{
        /* The SENSE register is assumed to be 32-bit. */
        int bitfield_width = p->sense_bitfield_width;
        int shift = 32 - (irq + 1) * bitfield_width;

        dev_dbg(&p->pdev->dev, "sense irq = %d, mode = %d\n", irq, value);

        if (value >= (1 << bitfield_width))
                return -EINVAL;

        intc_irqpin_read_modify_write(p, INTC_IRQPIN_REG_SENSE, shift,
                                      bitfield_width, value);
        return 0;
}

static void intc_irqpin_dbg(struct intc_irqpin_irq *i, char *str)
{
        dev_dbg(&i->p->pdev->dev, "%s (%d:%d:%d)\n",
                str, i->requested_irq, i->hw_irq, i->domain_irq);
}

static void intc_irqpin_irq_enable(struct irq_data *d)
{
        struct intc_irqpin_priv *p = irq_data_get_irq_chip_data(d);
        int hw_irq = irqd_to_hwirq(d);

        intc_irqpin_dbg(&p->irq[hw_irq], "enable");
        intc_irqpin_irq_write_hwirq(p, INTC_IRQPIN_REG_CLEAR, hw_irq);
}

static void intc_irqpin_irq_disable(struct irq_data *d)
{
        struct intc_irqpin_priv *p = irq_data_get_irq_chip_data(d);
        int hw_irq = irqd_to_hwirq(d);

        intc_irqpin_dbg(&p->irq[hw_irq], "disable");
        intc_irqpin_irq_write_hwirq(p, INTC_IRQPIN_REG_MASK, hw_irq);
}

static void intc_irqpin_shared_irq_enable(struct irq_data *d)
{
        struct intc_irqpin_priv *p = irq_data_get_irq_chip_data(d);
        int hw_irq = irqd_to_hwirq(d);

        intc_irqpin_dbg(&p->irq[hw_irq], "shared enable");
        intc_irqpin_irq_write_hwirq(p, INTC_IRQPIN_REG_CLEAR, hw_irq);

        p->shared_irq_mask &= ~BIT(hw_irq);
}

static void intc_irqpin_shared_irq_disable(struct irq_data *d)
{
        struct intc_irqpin_priv *p = irq_data_get_irq_chip_data(d);
        int hw_irq = irqd_to_hwirq(d);

        intc_irqpin_dbg(&p->irq[hw_irq], "shared disable");
        intc_irqpin_irq_write_hwirq(p, INTC_IRQPIN_REG_MASK, hw_irq);

        p->shared_irq_mask |= BIT(hw_irq);
}

static void intc_irqpin_irq_enable_force(struct irq_data *d)
{
        struct intc_irqpin_priv *p = irq_data_get_irq_chip_data(d);
        int irq = p->irq[irqd_to_hwirq(d)].requested_irq;

        intc_irqpin_irq_enable(d);

        /* enable interrupt through parent interrupt controller,
         * assumes non-shared interrupt with 1:1 mapping
         * needed for busted IRQs on some SoCs like sh73a0
         */
        irq_get_chip(irq)->irq_unmask(irq_get_irq_data(irq));
}

static void intc_irqpin_irq_disable_force(struct irq_data *d)
{
        struct intc_irqpin_priv *p = irq_data_get_irq_chip_data(d);
        int irq = p->irq[irqd_to_hwirq(d)].requested_irq;

        /* disable interrupt through parent interrupt controller,
         * assumes non-shared interrupt with 1:1 mapping
         * needed for busted IRQs on some SoCs like sh73a0
         */
        irq_get_chip(irq)->irq_mask(irq_get_irq_data(irq));
        intc_irqpin_irq_disable(d);
}

#define INTC_IRQ_SENSE_VALID 0x10
#define INTC_IRQ_SENSE(x) (x + INTC_IRQ_SENSE_VALID)

static unsigned char intc_irqpin_sense[IRQ_TYPE_SENSE_MASK + 1] = {
        [IRQ_TYPE_EDGE_FALLING] = INTC_IRQ_SENSE(0x00),
        [IRQ_TYPE_EDGE_RISING] = INTC_IRQ_SENSE(0x01),
        [IRQ_TYPE_LEVEL_LOW] = INTC_IRQ_SENSE(0x02),
        [IRQ_TYPE_LEVEL_HIGH] = INTC_IRQ_SENSE(0x03),
        [IRQ_TYPE_EDGE_BOTH] = INTC_IRQ_SENSE(0x04),
};

static int intc_irqpin_irq_set_type(struct irq_data *d, unsigned int type)
{
        unsigned char value = intc_irqpin_sense[type & IRQ_TYPE_SENSE_MASK];
        struct intc_irqpin_priv *p = irq_data_get_irq_chip_data(d);

        if (!(value & INTC_IRQ_SENSE_VALID))
                return -EINVAL;

        return intc_irqpin_set_sense(p, irqd_to_hwirq(d),
                                     value ^ INTC_IRQ_SENSE_VALID);
}

static int intc_irqpin_irq_set_wake(struct irq_data *d, unsigned int on)
{
        struct intc_irqpin_priv *p = irq_data_get_irq_chip_data(d);
        int hw_irq = irqd_to_hwirq(d);

        irq_set_irq_wake(p->irq[hw_irq].requested_irq, on);
        if (on)
                atomic_inc(&p->wakeup_path);
        else
                atomic_dec(&p->wakeup_path);

        return 0;
}

static irqreturn_t intc_irqpin_irq_handler(int irq, void *dev_id)
{
        struct intc_irqpin_irq *i = dev_id;
        struct intc_irqpin_priv *p = i->p;
        unsigned long bit;

        intc_irqpin_dbg(i, "demux1");
        bit = intc_irqpin_hwirq_mask(p, INTC_IRQPIN_REG_SOURCE, i->hw_irq);

        if (intc_irqpin_read(p, INTC_IRQPIN_REG_SOURCE) & bit) {
                intc_irqpin_write(p, INTC_IRQPIN_REG_SOURCE, ~bit);
                intc_irqpin_dbg(i, "demux2");
                generic_handle_irq(i->domain_irq);
                return IRQ_HANDLED;
        }
        return IRQ_NONE;
}

static irqreturn_t intc_irqpin_shared_irq_handler(int irq, void *dev_id)
{
        struct intc_irqpin_priv *p = dev_id;
        unsigned int reg_source = intc_irqpin_read(p, INTC_IRQPIN_REG_SOURCE);
        irqreturn_t status = IRQ_NONE;
        int k;

        for (k = 0; k < 8; k++) {
                if (reg_source & BIT(7 - k)) {
                        if (BIT(k) & p->shared_irq_mask)
                                continue;

                        status |= intc_irqpin_irq_handler(irq, &p->irq[k]);
                }
        }

        return status;
}

/*
 * This lock class tells lockdep that INTC External IRQ Pin irqs are in a
 * different category than their parents, so it won't report false recursion.
 */
static struct lock_class_key intc_irqpin_irq_lock_class;

/* And this is for the request mutex */
static struct lock_class_key intc_irqpin_irq_request_class;

static int intc_irqpin_irq_domain_map(struct irq_domain *h, unsigned int virq,
                                      irq_hw_number_t hw)
{
        struct intc_irqpin_priv *p = h->host_data;

        p->irq[hw].domain_irq = virq;
        p->irq[hw].hw_irq = hw;

        intc_irqpin_dbg(&p->irq[hw], "map");
        irq_set_chip_data(virq, h->host_data);
        irq_set_lockdep_class(virq, &intc_irqpin_irq_lock_class,
                              &intc_irqpin_irq_request_class);
        irq_set_chip_and_handler(virq, &p->irq_chip, handle_level_irq);
        return 0;
}

static const struct irq_domain_ops intc_irqpin_irq_domain_ops = {
        .map    = intc_irqpin_irq_domain_map,
        .xlate  = irq_domain_xlate_twocell,
};

static const struct intc_irqpin_config intc_irqpin_irlm_r8a777x = {
        .irlm_bit = 23, /* ICR0.IRLM0 */
        .needs_irlm = 1,
};

static const struct intc_irqpin_config intc_irqpin_rmobile = {
        .needs_irlm = 0,
};

static const struct of_device_id intc_irqpin_dt_ids[] = {
        { .compatible = "renesas,intc-irqpin", },
        { .compatible = "renesas,intc-irqpin-r8a7778",
          .data = &intc_irqpin_irlm_r8a777x },
        { .compatible = "renesas,intc-irqpin-r8a7779",
          .data = &intc_irqpin_irlm_r8a777x },
        { .compatible = "renesas,intc-irqpin-r8a7740",
          .data = &intc_irqpin_rmobile },
        { .compatible = "renesas,intc-irqpin-sh73a0",
          .data = &intc_irqpin_rmobile },
        {},
};
MODULE_DEVICE_TABLE(of, intc_irqpin_dt_ids);

static int intc_irqpin_probe(struct platform_device *pdev)
{
        const struct intc_irqpin_config *config;
        struct device *dev = &pdev->dev;
        struct intc_irqpin_priv *p;
        struct intc_irqpin_iomem *i;
        struct resource *io[INTC_IRQPIN_REG_NR];
        struct resource *irq;
        struct irq_chip *irq_chip;
        void (*enable_fn)(struct irq_data *d);
        void (*disable_fn)(struct irq_data *d);
        const char *name = dev_name(dev);
        bool control_parent;
        unsigned int nirqs;
        int ref_irq;
        int ret;
        int k;

        p = devm_kzalloc(dev, sizeof(*p), GFP_KERNEL);
        if (!p) {
                dev_err(dev, "failed to allocate driver data\n");
                return -ENOMEM;
        }

        /* deal with driver instance configuration */
        of_property_read_u32(dev->of_node, "sense-bitfield-width",
                             &p->sense_bitfield_width);
        control_parent = of_property_read_bool(dev->of_node, "control-parent");
        if (!p->sense_bitfield_width)
                p->sense_bitfield_width = 4; /* default to 4 bits */

        p->pdev = pdev;
        platform_set_drvdata(pdev, p);

        config = of_device_get_match_data(dev);

        pm_runtime_enable(dev);
        pm_runtime_get_sync(dev);

        /* get hold of register banks */
        memset(io, 0, sizeof(io));
        for (k = 0; k < INTC_IRQPIN_REG_NR; k++) {
                io[k] = platform_get_resource(pdev, IORESOURCE_MEM, k);
                if (!io[k] && k < INTC_IRQPIN_REG_NR_MANDATORY) {
                        dev_err(dev, "not enough IOMEM resources\n");
                        ret = -EINVAL;
                        goto err0;
                }
        }

        /* allow any number of IRQs between 1 and INTC_IRQPIN_MAX */
        for (k = 0; k < INTC_IRQPIN_MAX; k++) {
                irq = platform_get_resource(pdev, IORESOURCE_IRQ, k);
                if (!irq)
                        break;

                p->irq[k].p = p;
                p->irq[k].requested_irq = irq->start;
        }

        nirqs = k;
        if (nirqs < 1) {
                dev_err(dev, "not enough IRQ resources\n");
                ret = -EINVAL;
                goto err0;
        }

        /* ioremap IOMEM and setup read/write callbacks */
        for (k = 0; k < INTC_IRQPIN_REG_NR; k++) {
                i = &p->iomem[k];

                /* handle optional registers */
                if (!io[k])
                        continue;

                switch (resource_size(io[k])) {
                case 1:
                        i->width = 8;
                        i->read = intc_irqpin_read8;
                        i->write = intc_irqpin_write8;
                        break;
                case 4:
                        i->width = 32;
                        i->read = intc_irqpin_read32;
                        i->write = intc_irqpin_write32;
                        break;
                default:
                        dev_err(dev, "IOMEM size mismatch\n");
                        ret = -EINVAL;
                        goto err0;
                }

                i->iomem = devm_ioremap_nocache(dev, io[k]->start,
                                                resource_size(io[k]));
                if (!i->iomem) {
                        dev_err(dev, "failed to remap IOMEM\n");
                        ret = -ENXIO;
                        goto err0;
                }
        }

        /* configure "individual IRQ mode" where needed */
        if (config && config->needs_irlm) {
                if (io[INTC_IRQPIN_REG_IRLM])
                        intc_irqpin_read_modify_write(p, INTC_IRQPIN_REG_IRLM,
                                                      config->irlm_bit, 1, 1);
                else
                        dev_warn(dev, "unable to select IRLM mode\n");
        }

        /* mask all interrupts using priority */
        for (k = 0; k < nirqs; k++)
                intc_irqpin_mask_unmask_prio(p, k, 1);

        /* clear all pending interrupts */
        intc_irqpin_write(p, INTC_IRQPIN_REG_SOURCE, 0x0);

        /* scan for shared interrupt lines */
        ref_irq = p->irq[0].requested_irq;
        p->shared_irqs = 1;
        for (k = 1; k < nirqs; k++) {
                if (ref_irq != p->irq[k].requested_irq) {
                        p->shared_irqs = 0;
                        break;
                }
        }

        /* use more severe masking method if requested */
        if (control_parent) {
                enable_fn = intc_irqpin_irq_enable_force;
                disable_fn = intc_irqpin_irq_disable_force;
        } else if (!p->shared_irqs) {
                enable_fn = intc_irqpin_irq_enable;
                disable_fn = intc_irqpin_irq_disable;
        } else {
                enable_fn = intc_irqpin_shared_irq_enable;
                disable_fn = intc_irqpin_shared_irq_disable;
        }

        irq_chip = &p->irq_chip;
        irq_chip->name = name;
        irq_chip->irq_mask = disable_fn;
        irq_chip->irq_unmask = enable_fn;
        irq_chip->irq_set_type = intc_irqpin_irq_set_type;
        irq_chip->irq_set_wake = intc_irqpin_irq_set_wake;
        irq_chip->flags = IRQCHIP_MASK_ON_SUSPEND;

        p->irq_domain = irq_domain_add_simple(dev->of_node, nirqs, 0,
                                              &intc_irqpin_irq_domain_ops, p);
        if (!p->irq_domain) {
                ret = -ENXIO;
                dev_err(dev, "cannot initialize irq domain\n");
                goto err0;
        }

        if (p->shared_irqs) {
                /* request one shared interrupt */
                if (devm_request_irq(dev, p->irq[0].requested_irq,
                                intc_irqpin_shared_irq_handler,
                                IRQF_SHARED, name, p)) {
                        dev_err(dev, "failed to request low IRQ\n");
                        ret = -ENOENT;
                        goto err1;
                }
        } else {
                /* request interrupts one by one */
                for (k = 0; k < nirqs; k++) {
                        if (devm_request_irq(dev, p->irq[k].requested_irq,
                                             intc_irqpin_irq_handler, 0, name,
                                             &p->irq[k])) {
                                dev_err(dev, "failed to request low IRQ\n");
                                ret = -ENOENT;
                                goto err1;
                        }
                }
        }

        /* unmask all interrupts on prio level */
        for (k = 0; k < nirqs; k++)
                intc_irqpin_mask_unmask_prio(p, k, 0);

        dev_info(dev, "driving %d irqs\n", nirqs);

        return 0;

err1:
        irq_domain_remove(p->irq_domain);
err0:
        pm_runtime_put(dev);
        pm_runtime_disable(dev);
        return ret;
}

static int intc_irqpin_remove(struct platform_device *pdev)
{
        struct intc_irqpin_priv *p = platform_get_drvdata(pdev);

        irq_domain_remove(p->irq_domain);
        pm_runtime_put(&pdev->dev);
        pm_runtime_disable(&pdev->dev);
        return 0;
}

static int __maybe_unused intc_irqpin_suspend(struct device *dev)
{
        struct intc_irqpin_priv *p = dev_get_drvdata(dev);

        if (atomic_read(&p->wakeup_path))
                device_set_wakeup_path(dev);

        return 0;
}

static SIMPLE_DEV_PM_OPS(intc_irqpin_pm_ops, intc_irqpin_suspend, NULL);

static struct platform_driver intc_irqpin_device_driver = {
        .probe          = intc_irqpin_probe,
        .remove         = intc_irqpin_remove,
        .driver         = {
                .name   = "renesas_intc_irqpin",
                .of_match_table = intc_irqpin_dt_ids,
                .pm     = &intc_irqpin_pm_ops,
        }
};

static int __init intc_irqpin_init(void)
{
        return platform_driver_register(&intc_irqpin_device_driver);
}
postcore_initcall(intc_irqpin_init);

static void __exit intc_irqpin_exit(void)
{
        platform_driver_unregister(&intc_irqpin_device_driver);
}
module_exit(intc_irqpin_exit);

MODULE_AUTHOR("Magnus Damm");
MODULE_DESCRIPTION("Renesas INTC External IRQ Pin Driver");
MODULE_LICENSE("GPL v2");