/*
 * Support for virtual IRQ subgroups.
 *
 * Copyright (C) 2010  Paul Mundt
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */
#define pr_fmt(fmt) "intc: " fmt

#include <linux/slab.h>
#include <linux/irq.h>
#include <linux/list.h>
#include <linux/radix-tree.h>
#include <linux/spinlock.h>
#include <linux/export.h>
#include "internals.h"

static struct intc_map_entry intc_irq_xlate[INTC_NR_IRQS];

struct intc_virq_list {
        unsigned int irq;
        struct intc_virq_list *next;
};

#define for_each_virq(entry, head) \
        for (entry = head; entry; entry = entry->next)

/*
 * Tags for the radix tree
 */
#define INTC_TAG_VIRQ_NEEDS_ALLOC       0

void intc_irq_xlate_set(unsigned int irq, intc_enum id, struct intc_desc_int *d)
{
        unsigned long flags;

        raw_spin_lock_irqsave(&intc_big_lock, flags);
        intc_irq_xlate[irq].enum_id = id;
        intc_irq_xlate[irq].desc = d;
        raw_spin_unlock_irqrestore(&intc_big_lock, flags);
}

struct intc_map_entry *intc_irq_xlate_get(unsigned int irq)
{
        return intc_irq_xlate + irq;
}

int intc_irq_lookup(const char *chipname, intc_enum enum_id)
{
        struct intc_map_entry *ptr;
        struct intc_desc_int *d;
        int irq = -1;

        list_for_each_entry(d, &intc_list, list) {
                int tagged;

                if (strcmp(d->chip.name, chipname) != 0)
                        continue;

                /*
                 * Catch early lookups for subgroup VIRQs that have not
                 * yet been allocated an IRQ. This already includes a
                 * fast-path out if the tree is untagged, so there is no
                 * need to explicitly test the root tree.
                 */
                tagged = radix_tree_tag_get(&d->tree, enum_id,
                                            INTC_TAG_VIRQ_NEEDS_ALLOC);
                if (unlikely(tagged))
                        break;

                ptr = radix_tree_lookup(&d->tree, enum_id);
                if (ptr) {
                        irq = ptr - intc_irq_xlate;
                        break;
                }
        }

        return irq;
}
EXPORT_SYMBOL_GPL(intc_irq_lookup);

static int add_virq_to_pirq(unsigned int irq, unsigned int virq)
{
        struct intc_virq_list *entry;
        struct intc_virq_list **last = NULL;

        /* scan for duplicates */
        for_each_virq(entry, irq_get_handler_data(irq)) {
                if (entry->irq == virq)
                        return 0;
                last = &entry->next;
        }

        entry = kzalloc(sizeof(struct intc_virq_list), GFP_ATOMIC);
        if (!entry)
                return -ENOMEM;

        entry->irq = virq;

        if (last)
                *last = entry;
        else
                irq_set_handler_data(irq, entry);

        return 0;
}

static void intc_virq_handler(struct irq_desc *desc)
{
        unsigned int irq = irq_desc_get_irq(desc);
        struct irq_data *data = irq_desc_get_irq_data(desc);
        struct irq_chip *chip = irq_data_get_irq_chip(data);
        struct intc_virq_list *entry, *vlist = irq_data_get_irq_handler_data(data);
        struct intc_desc_int *d = get_intc_desc(irq);

        chip->irq_mask_ack(data);

        for_each_virq(entry, vlist) {
                unsigned long addr, handle;
                struct irq_desc *vdesc = irq_to_desc(entry->irq);

                if (vdesc) {
                        handle = (unsigned long)irq_desc_get_handler_data(vdesc);
                        addr = INTC_REG(d, _INTC_ADDR_E(handle), 0);
                        if (intc_reg_fns[_INTC_FN(handle)](addr, handle, 0))
                                generic_handle_irq_desc(vdesc);
                }
        }

        chip->irq_unmask(data);
}

static unsigned long __init intc_subgroup_data(struct intc_subgroup *subgroup,
                                               struct intc_desc_int *d,
                                               unsigned int index)
{
        unsigned int fn = REG_FN_TEST_BASE + (subgroup->reg_width >> 3) - 1;

        return _INTC_MK(fn, MODE_ENABLE_REG, intc_get_reg(d, subgroup->reg),
                        0, 1, (subgroup->reg_width - 1) - index);
}

static void __init intc_subgroup_init_one(struct intc_desc *desc,
                                          struct intc_desc_int *d,
                                          struct intc_subgroup *subgroup)
{
        struct intc_map_entry *mapped;
        unsigned int pirq;
        unsigned long flags;
        int i;

        mapped = radix_tree_lookup(&d->tree, subgroup->parent_id);
        if (!mapped) {
                WARN_ON(1);
                return;
        }

        pirq = mapped - intc_irq_xlate;

        raw_spin_lock_irqsave(&d->lock, flags);

        for (i = 0; i < ARRAY_SIZE(subgroup->enum_ids); i++) {
                struct intc_subgroup_entry *entry;
                int err;

                if (!subgroup->enum_ids[i])
                        continue;

                entry = kmalloc(sizeof(*entry), GFP_NOWAIT);
                if (!entry)
                        break;

                entry->pirq = pirq;
                entry->enum_id = subgroup->enum_ids[i];
                entry->handle = intc_subgroup_data(subgroup, d, i);

                err = radix_tree_insert(&d->tree, entry->enum_id, entry);
                if (unlikely(err < 0))
                        break;

                radix_tree_tag_set(&d->tree, entry->enum_id,
                                   INTC_TAG_VIRQ_NEEDS_ALLOC);
        }

        raw_spin_unlock_irqrestore(&d->lock, flags);
}

void __init intc_subgroup_init(struct intc_desc *desc, struct intc_desc_int *d)
{
        int i;

        if (!desc->hw.subgroups)
                return;

        for (i = 0; i < desc->hw.nr_subgroups; i++)
                intc_subgroup_init_one(desc, d, desc->hw.subgroups + i);
}

static void __init intc_subgroup_map(struct intc_desc_int *d)
{
        struct intc_subgroup_entry *entries[32];
        unsigned long flags;
        unsigned int nr_found;
        int i;

        raw_spin_lock_irqsave(&d->lock, flags);

restart:
        nr_found = radix_tree_gang_lookup_tag_slot(&d->tree,
                        (void ***)entries, 0, ARRAY_SIZE(entries),
                        INTC_TAG_VIRQ_NEEDS_ALLOC);

        for (i = 0; i < nr_found; i++) {
                struct intc_subgroup_entry *entry;
                int irq;

                entry = radix_tree_deref_slot((void **)entries[i]);
                if (unlikely(!entry))
                        continue;
                if (radix_tree_deref_retry(entry))
                        goto restart;

                irq = irq_alloc_desc(numa_node_id());
                if (unlikely(irq < 0)) {
                        pr_err("no more free IRQs, bailing..\n");
                        break;
                }

                activate_irq(irq);

                pr_info("Setting up a chained VIRQ from %d -> %d\n",
                        irq, entry->pirq);

                intc_irq_xlate_set(irq, entry->enum_id, d);

                irq_set_chip_and_handler_name(irq, irq_get_chip(entry->pirq),
                                              handle_simple_irq, "virq");
                irq_set_chip_data(irq, irq_get_chip_data(entry->pirq));

                irq_set_handler_data(irq, (void *)entry->handle);

                /*
                 * Set the virtual IRQ as non-threadable.
                 */
                irq_set_nothread(irq);

                /* Set handler data before installing the handler */
                add_virq_to_pirq(entry->pirq, irq);
                irq_set_chained_handler(entry->pirq, intc_virq_handler);

                radix_tree_tag_clear(&d->tree, entry->enum_id,
                                     INTC_TAG_VIRQ_NEEDS_ALLOC);
                radix_tree_replace_slot(&d->tree, (void **)entries[i],
                                        &intc_irq_xlate[irq]);
        }

        raw_spin_unlock_irqrestore(&d->lock, flags);
}

void __init intc_finalize(void)
{
        struct intc_desc_int *d;

        list_for_each_entry(d, &intc_list, list)
                if (radix_tree_tagged(&d->tree, INTC_TAG_VIRQ_NEEDS_ALLOC))
                        intc_subgroup_map(d);
}