// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * This file implements an irqchip for OPAL events. Whenever there is
 * an interrupt that is handled by OPAL we get passed a list of events
 * that Linux needs to do something about. These basically look like
 * interrupts to Linux so we implement an irqchip to handle them.
 *
 * Copyright Alistair Popple, IBM Corporation 2014.
 */
#include <linux/bitops.h>
#include <linux/irq.h>
#include <linux/irqchip.h>
#include <linux/irqdomain.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/kthread.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/of_irq.h>

#include <asm/machdep.h>
#include <asm/opal.h>

#include "powernv.h"

/* Maximum number of events supported by OPAL firmware */
#define MAX_NUM_EVENTS 64

struct opal_event_irqchip {
        struct irq_chip irqchip;
        struct irq_domain *domain;
        unsigned long mask;
};
static struct opal_event_irqchip opal_event_irqchip;
static u64 last_outstanding_events;
static int opal_irq_count;
static struct resource *opal_irqs;

void opal_handle_events(void)
{
        __be64 events = 0;
        u64 e;

        e = READ_ONCE(last_outstanding_events) & opal_event_irqchip.mask;
again:
        while (e) {
                int hwirq;

                hwirq = fls64(e) - 1;
                e &= ~BIT_ULL(hwirq);

                local_irq_disable();
                irq_enter();
                generic_handle_domain_irq(opal_event_irqchip.domain, hwirq);
                irq_exit();
                local_irq_enable();

                cond_resched();
        }
        last_outstanding_events = 0;
        if (opal_poll_events(&events) != OPAL_SUCCESS)
                return;
        e = be64_to_cpu(events) & opal_event_irqchip.mask;
        if (e)
                goto again;
}

bool opal_have_pending_events(void)
{
        if (last_outstanding_events & opal_event_irqchip.mask)
                return true;
        return false;
}

static void opal_event_mask(struct irq_data *d)
{
        clear_bit(d->hwirq, &opal_event_irqchip.mask);
}

static void opal_event_unmask(struct irq_data *d)
{
        set_bit(d->hwirq, &opal_event_irqchip.mask);
        if (opal_have_pending_events())
                opal_wake_poller();
}

static int opal_event_set_type(struct irq_data *d, unsigned int flow_type)
{
        /*
         * For now we only support level triggered events. The irq
         * handler will be called continuously until the event has
         * been cleared in OPAL.
         */
        if (flow_type != IRQ_TYPE_LEVEL_HIGH)
                return -EINVAL;

        return 0;
}

static struct opal_event_irqchip opal_event_irqchip = {
        .irqchip = {
                .name = "OPAL EVT",
                .irq_mask = opal_event_mask,
                .irq_unmask = opal_event_unmask,
                .irq_set_type = opal_event_set_type,
        },
        .mask = 0,
};

static int opal_event_map(struct irq_domain *d, unsigned int irq,
                        irq_hw_number_t hwirq)
{
        irq_set_chip_data(irq, &opal_event_irqchip);
        irq_set_chip_and_handler(irq, &opal_event_irqchip.irqchip,
                                handle_level_irq);

        return 0;
}

static irqreturn_t opal_interrupt(int irq, void *data)
{
        __be64 events;

        opal_handle_interrupt(virq_to_hw(irq), &events);
        last_outstanding_events = be64_to_cpu(events);
        if (opal_have_pending_events())
                opal_wake_poller();

        return IRQ_HANDLED;
}

static int opal_event_match(struct irq_domain *h, struct device_node *node,
                            enum irq_domain_bus_token bus_token)
{
        return irq_domain_get_of_node(h) == node;
}

static int opal_event_xlate(struct irq_domain *h, struct device_node *np,
                           const u32 *intspec, unsigned int intsize,
                           irq_hw_number_t *out_hwirq, unsigned int *out_flags)
{
        *out_hwirq = intspec[0];
        *out_flags = IRQ_TYPE_LEVEL_HIGH;

        return 0;
}

static const struct irq_domain_ops opal_event_domain_ops = {
        .match  = opal_event_match,
        .map    = opal_event_map,
        .xlate  = opal_event_xlate,
};

void opal_event_shutdown(void)
{
        unsigned int i;

        /* First free interrupts, which will also mask them */
        for (i = 0; i < opal_irq_count; i++) {
                if (!opal_irqs || !opal_irqs[i].start)
                        continue;

                if (in_interrupt() || irqs_disabled())
                        disable_irq_nosync(opal_irqs[i].start);
                else
                        free_irq(opal_irqs[i].start, NULL);

                opal_irqs[i].start = 0;
        }
}

int __init opal_event_init(void)
{
        struct device_node *dn, *opal_node;
        bool old_style = false;
        int i, rc = 0;

        opal_node = of_find_node_by_path("/ibm,opal");
        if (!opal_node) {
                pr_warn("opal: Node not found\n");
                return -ENODEV;
        }

        /* If dn is NULL it means the domain won't be linked to a DT
         * node so therefore irq_of_parse_and_map(...) wont work. But
         * that shouldn't be problem because if we're running a
         * version of skiboot that doesn't have the dn then the
         * devices won't have the correct properties and will have to
         * fall back to the legacy method (opal_event_request(...))
         * anyway. */
        dn = of_find_compatible_node(NULL, NULL, "ibm,opal-event");
        opal_event_irqchip.domain = irq_domain_add_linear(dn, MAX_NUM_EVENTS,
                                &opal_event_domain_ops, &opal_event_irqchip);
        of_node_put(dn);
        if (!opal_event_irqchip.domain) {
                pr_warn("opal: Unable to create irq domain\n");
                rc = -ENOMEM;
                goto out;
        }

        /* Look for new-style (standard) "interrupts" property */
        opal_irq_count = of_irq_count(opal_node);

        /* Absent ? Look for the old one */
        if (opal_irq_count < 1) {
                /* Get opal-interrupts property and names if present */
                rc = of_property_count_u32_elems(opal_node, "opal-interrupts");
                if (rc > 0)
                        opal_irq_count = rc;
                old_style = true;
        }

        /* No interrupts ? Bail out */
        if (!opal_irq_count)
                goto out;

        pr_debug("OPAL: Found %d interrupts reserved for OPAL using %s scheme\n",
                 opal_irq_count, old_style ? "old" : "new");

        /* Allocate an IRQ resources array */
        opal_irqs = kcalloc(opal_irq_count, sizeof(struct resource), GFP_KERNEL);
        if (WARN_ON(!opal_irqs)) {
                rc = -ENOMEM;
                goto out;
        }

        /* Build the resources array */
        if (old_style) {
                /* Old style "opal-interrupts" property */
                for (i = 0; i < opal_irq_count; i++) {
                        struct resource *r = &opal_irqs[i];
                        const char *name = NULL;
                        u32 hw_irq;
                        int virq;

                        rc = of_property_read_u32_index(opal_node, "opal-interrupts",
                                                        i, &hw_irq);
                        if (WARN_ON(rc < 0)) {
                                opal_irq_count = i;
                                break;
                        }
                        of_property_read_string_index(opal_node, "opal-interrupts-names",
                                                      i, &name);
                        virq = irq_create_mapping(NULL, hw_irq);
                        if (!virq) {
                                pr_warn("Failed to map OPAL irq 0x%x\n", hw_irq);
                                continue;
                        }
                        r->start = r->end = virq;
                        r->flags = IORESOURCE_IRQ | IRQ_TYPE_LEVEL_LOW;
                        r->name = name;
                }
        } else {
                /* new style standard "interrupts" property */
                rc = of_irq_to_resource_table(opal_node, opal_irqs, opal_irq_count);
                if (WARN_ON(rc < 0)) {
                        opal_irq_count = 0;
                        kfree(opal_irqs);
                        goto out;
                }
                if (WARN_ON(rc < opal_irq_count))
                        opal_irq_count = rc;
        }

        /* Install interrupt handlers */
        for (i = 0; i < opal_irq_count; i++) {
                struct resource *r = &opal_irqs[i];
                const char *name;

                /* Prefix name */
                if (r->name && strlen(r->name))
                        name = kasprintf(GFP_KERNEL, "opal-%s", r->name);
                else
                        name = kasprintf(GFP_KERNEL, "opal");

                /* Install interrupt handler */
                rc = request_irq(r->start, opal_interrupt, r->flags & IRQD_TRIGGER_MASK,
                                 name, NULL);
                if (rc) {
                        pr_warn("Error %d requesting OPAL irq %d\n", rc, (int)r->start);
                        continue;
                }
        }
        rc = 0;
 out:
        of_node_put(opal_node);
        return rc;
}
machine_arch_initcall(powernv, opal_event_init);

/**
 * opal_event_request(unsigned int opal_event_nr) - Request an event
 * @opal_event_nr: the opal event number to request
 *
 * This routine can be used to find the linux virq number which can
 * then be passed to request_irq to assign a handler for a particular
 * opal event. This should only be used by legacy devices which don't
 * have proper device tree bindings. Most devices should use
 * irq_of_parse_and_map() instead.
 */
int opal_event_request(unsigned int opal_event_nr)
{
        if (WARN_ON_ONCE(!opal_event_irqchip.domain))
                return 0;

        return irq_create_mapping(opal_event_irqchip.domain, opal_event_nr);
}
EXPORT_SYMBOL(opal_event_request);