// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 2016,2017 IBM Corporation.
 */

#define pr_fmt(fmt) "xive: " fmt

#include <linux/types.h>
#include <linux/threads.h>
#include <linux/kernel.h>
#include <linux/irq.h>
#include <linux/debugfs.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/msi.h>

#include <asm/prom.h>
#include <asm/io.h>
#include <asm/smp.h>
#include <asm/machdep.h>
#include <asm/irq.h>
#include <asm/errno.h>
#include <asm/xive.h>
#include <asm/xive-regs.h>
#include <asm/xmon.h>

#include "xive-internal.h"

#undef DEBUG_FLUSH
#undef DEBUG_ALL

#ifdef DEBUG_ALL
#define DBG_VERBOSE(fmt, ...)   pr_devel("cpu %d - " fmt, \
                                         smp_processor_id(), ## __VA_ARGS__)
#else
#define DBG_VERBOSE(fmt...)     do { } while(0)
#endif

bool __xive_enabled;
EXPORT_SYMBOL_GPL(__xive_enabled);
bool xive_cmdline_disabled;

/* We use only one priority for now */
static u8 xive_irq_priority;

/* TIMA exported to KVM */
void __iomem *xive_tima;
EXPORT_SYMBOL_GPL(xive_tima);
u32 xive_tima_offset;

/* Backend ops */
static const struct xive_ops *xive_ops;

/* Our global interrupt domain */
static struct irq_domain *xive_irq_domain;

#ifdef CONFIG_SMP
/* The IPIs all use the same logical irq number */
static u32 xive_ipi_irq;
#endif

/* Xive state for each CPU */
static DEFINE_PER_CPU(struct xive_cpu *, xive_cpu);

/*
 * A "disabled" interrupt should never fire, to catch problems
 * we set its logical number to this
 */
#define XIVE_BAD_IRQ            0x7fffffff
#define XIVE_MAX_IRQ            (XIVE_BAD_IRQ - 1)

/* An invalid CPU target */
#define XIVE_INVALID_TARGET     (-1)

/*
 * Read the next entry in a queue, return its content if it's valid
 * or 0 if there is no new entry.
 *
 * The queue pointer is moved forward unless "just_peek" is set
 */
static u32 xive_read_eq(struct xive_q *q, bool just_peek)
{
        u32 cur;

        if (!q->qpage)
                return 0;
        cur = be32_to_cpup(q->qpage + q->idx);

        /* Check valid bit (31) vs current toggle polarity */
        if ((cur >> 31) == q->toggle)
                return 0;

        /* If consuming from the queue ... */
        if (!just_peek) {
                /* Next entry */
                q->idx = (q->idx + 1) & q->msk;

                /* Wrap around: flip valid toggle */
                if (q->idx == 0)
                        q->toggle ^= 1;
        }
        /* Mask out the valid bit (31) */
        return cur & 0x7fffffff;
}

/*
 * Scans all the queue that may have interrupts in them
 * (based on "pending_prio") in priority order until an
 * interrupt is found or all the queues are empty.
 *
 * Then updates the CPPR (Current Processor Priority
 * Register) based on the most favored interrupt found
 * (0xff if none) and return what was found (0 if none).
 *
 * If just_peek is set, return the most favored pending
 * interrupt if any but don't update the queue pointers.
 *
 * Note: This function can operate generically on any number
 * of queues (up to 8). The current implementation of the XIVE
 * driver only uses a single queue however.
 *
 * Note2: This will also "flush" "the pending_count" of a queue
 * into the "count" when that queue is observed to be empty.
 * This is used to keep track of the amount of interrupts
 * targetting a queue. When an interrupt is moved away from
 * a queue, we only decrement that queue count once the queue
 * has been observed empty to avoid races.
 */
static u32 xive_scan_interrupts(struct xive_cpu *xc, bool just_peek)
{
        u32 irq = 0;
        u8 prio = 0;

        /* Find highest pending priority */
        while (xc->pending_prio != 0) {
                struct xive_q *q;

                prio = ffs(xc->pending_prio) - 1;
                DBG_VERBOSE("scan_irq: trying prio %d\n", prio);

                /* Try to fetch */
                irq = xive_read_eq(&xc->queue[prio], just_peek);

                /* Found something ? That's it */
                if (irq) {
                        if (just_peek || irq_to_desc(irq))
                                break;
                        /*
                         * We should never get here; if we do then we must
                         * have failed to synchronize the interrupt properly
                         * when shutting it down.
                         */
                        pr_crit("xive: got interrupt %d without descriptor, dropping\n",
                                irq);
                        WARN_ON(1);
                        continue;
                }

                /* Clear pending bits */
                xc->pending_prio &= ~(1 << prio);

                /*
                 * Check if the queue count needs adjusting due to
                 * interrupts being moved away. See description of
                 * xive_dec_target_count()
                 */
                q = &xc->queue[prio];
                if (atomic_read(&q->pending_count)) {
                        int p = atomic_xchg(&q->pending_count, 0);
                        if (p) {
                                WARN_ON(p > atomic_read(&q->count));
                                atomic_sub(p, &q->count);
                        }
                }
        }

        /* If nothing was found, set CPPR to 0xff */
        if (irq == 0)
                prio = 0xff;

        /* Update HW CPPR to match if necessary */
        if (prio != xc->cppr) {
                DBG_VERBOSE("scan_irq: adjusting CPPR to %d\n", prio);
                xc->cppr = prio;
                out_8(xive_tima + xive_tima_offset + TM_CPPR, prio);
        }

        return irq;
}

/*
 * This is used to perform the magic loads from an ESB
 * described in xive-regs.h
 */
static notrace u8 xive_esb_read(struct xive_irq_data *xd, u32 offset)
{
        u64 val;

        /* Handle HW errata */
        if (xd->flags & XIVE_IRQ_FLAG_SHIFT_BUG)
                offset |= offset << 4;

        if ((xd->flags & XIVE_IRQ_FLAG_H_INT_ESB) && xive_ops->esb_rw)
                val = xive_ops->esb_rw(xd->hw_irq, offset, 0, 0);
        else
                val = in_be64(xd->eoi_mmio + offset);

        return (u8)val;
}

static void xive_esb_write(struct xive_irq_data *xd, u32 offset, u64 data)
{
        /* Handle HW errata */
        if (xd->flags & XIVE_IRQ_FLAG_SHIFT_BUG)
                offset |= offset << 4;

        if ((xd->flags & XIVE_IRQ_FLAG_H_INT_ESB) && xive_ops->esb_rw)
                xive_ops->esb_rw(xd->hw_irq, offset, data, 1);
        else
                out_be64(xd->eoi_mmio + offset, data);
}

#ifdef CONFIG_XMON
static notrace void xive_dump_eq(const char *name, struct xive_q *q)
{
        u32 i0, i1, idx;

        if (!q->qpage)
                return;
        idx = q->idx;
        i0 = be32_to_cpup(q->qpage + idx);
        idx = (idx + 1) & q->msk;
        i1 = be32_to_cpup(q->qpage + idx);
        xmon_printf("%s idx=%d T=%d %08x %08x ...", name,
                     q->idx, q->toggle, i0, i1);
}

notrace void xmon_xive_do_dump(int cpu)
{
        struct xive_cpu *xc = per_cpu(xive_cpu, cpu);

        xmon_printf("CPU %d:", cpu);
        if (xc) {
                xmon_printf("pp=%02x CPPR=%02x ", xc->pending_prio, xc->cppr);

#ifdef CONFIG_SMP
                {
                        u64 val = xive_esb_read(&xc->ipi_data, XIVE_ESB_GET);

                        xmon_printf("IPI=0x%08x PQ=%c%c ", xc->hw_ipi,
                                    val & XIVE_ESB_VAL_P ? 'P' : '-',
                                    val & XIVE_ESB_VAL_Q ? 'Q' : '-');
                }
#endif
                xive_dump_eq("EQ", &xc->queue[xive_irq_priority]);
        }
        xmon_printf("\n");
}

int xmon_xive_get_irq_config(u32 hw_irq, struct irq_data *d)
{
        int rc;
        u32 target;
        u8 prio;
        u32 lirq;

        rc = xive_ops->get_irq_config(hw_irq, &target, &prio, &lirq);
        if (rc) {
                xmon_printf("IRQ 0x%08x : no config rc=%d\n", hw_irq, rc);
                return rc;
        }

        xmon_printf("IRQ 0x%08x : target=0x%x prio=%02x lirq=0x%x ",
                    hw_irq, target, prio, lirq);

        if (d) {
                struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);
                u64 val = xive_esb_read(xd, XIVE_ESB_GET);

                xmon_printf("PQ=%c%c",
                            val & XIVE_ESB_VAL_P ? 'P' : '-',
                            val & XIVE_ESB_VAL_Q ? 'Q' : '-');
        }

        xmon_printf("\n");
        return 0;
}

#endif /* CONFIG_XMON */

static unsigned int xive_get_irq(void)
{
        struct xive_cpu *xc = __this_cpu_read(xive_cpu);
        u32 irq;

        /*
         * This can be called either as a result of a HW interrupt or
         * as a "replay" because EOI decided there was still something
         * in one of the queues.
         *
         * First we perform an ACK cycle in order to update our mask
         * of pending priorities. This will also have the effect of
         * updating the CPPR to the most favored pending interrupts.
         *
         * In the future, if we have a way to differentiate a first
         * entry (on HW interrupt) from a replay triggered by EOI,
         * we could skip this on replays unless we soft-mask tells us
         * that a new HW interrupt occurred.
         */
        xive_ops->update_pending(xc);

        DBG_VERBOSE("get_irq: pending=%02x\n", xc->pending_prio);

        /* Scan our queue(s) for interrupts */
        irq = xive_scan_interrupts(xc, false);

        DBG_VERBOSE("get_irq: got irq 0x%x, new pending=0x%02x\n",
            irq, xc->pending_prio);

        /* Return pending interrupt if any */
        if (irq == XIVE_BAD_IRQ)
                return 0;
        return irq;
}

/*
 * After EOI'ing an interrupt, we need to re-check the queue
 * to see if another interrupt is pending since multiple
 * interrupts can coalesce into a single notification to the
 * CPU.
 *
 * If we find that there is indeed more in there, we call
 * force_external_irq_replay() to make Linux synthetize an
 * external interrupt on the next call to local_irq_restore().
 */
static void xive_do_queue_eoi(struct xive_cpu *xc)
{
        if (xive_scan_interrupts(xc, true) != 0) {
                DBG_VERBOSE("eoi: pending=0x%02x\n", xc->pending_prio);
                force_external_irq_replay();
        }
}

/*
 * EOI an interrupt at the source. There are several methods
 * to do this depending on the HW version and source type
 */
static void xive_do_source_eoi(u32 hw_irq, struct xive_irq_data *xd)
{
        xd->stale_p = false;
        /* If the XIVE supports the new "store EOI facility, use it */
        if (xd->flags & XIVE_IRQ_FLAG_STORE_EOI)
                xive_esb_write(xd, XIVE_ESB_STORE_EOI, 0);
        else if (hw_irq && xd->flags & XIVE_IRQ_FLAG_EOI_FW) {
                /*
                 * The FW told us to call it. This happens for some
                 * interrupt sources that need additional HW whacking
                 * beyond the ESB manipulation. For example LPC interrupts
                 * on P9 DD1.0 needed a latch to be clared in the LPC bridge
                 * itself. The Firmware will take care of it.
                 */
                if (WARN_ON_ONCE(!xive_ops->eoi))
                        return;
                xive_ops->eoi(hw_irq);
        } else {
                u8 eoi_val;

                /*
                 * Otherwise for EOI, we use the special MMIO that does
                 * a clear of both P and Q and returns the old Q,
                 * except for LSIs where we use the "EOI cycle" special
                 * load.
                 *
                 * This allows us to then do a re-trigger if Q was set
                 * rather than synthesizing an interrupt in software
                 *
                 * For LSIs the HW EOI cycle is used rather than PQ bits,
                 * as they are automatically re-triggred in HW when still
                 * pending.
                 */
                if (xd->flags & XIVE_IRQ_FLAG_LSI)
                        xive_esb_read(xd, XIVE_ESB_LOAD_EOI);
                else {
                        eoi_val = xive_esb_read(xd, XIVE_ESB_SET_PQ_00);
                        DBG_VERBOSE("eoi_val=%x\n", eoi_val);

                        /* Re-trigger if needed */
                        if ((eoi_val & XIVE_ESB_VAL_Q) && xd->trig_mmio)
                                out_be64(xd->trig_mmio, 0);
                }
        }
}

/* irq_chip eoi callback, called with irq descriptor lock held */
static void xive_irq_eoi(struct irq_data *d)
{
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);
        struct xive_cpu *xc = __this_cpu_read(xive_cpu);

        DBG_VERBOSE("eoi_irq: irq=%d [0x%lx] pending=%02x\n",
                    d->irq, irqd_to_hwirq(d), xc->pending_prio);

        /*
         * EOI the source if it hasn't been disabled and hasn't
         * been passed-through to a KVM guest
         */
        if (!irqd_irq_disabled(d) && !irqd_is_forwarded_to_vcpu(d) &&
            !(xd->flags & XIVE_IRQ_NO_EOI))
                xive_do_source_eoi(irqd_to_hwirq(d), xd);
        else
                xd->stale_p = true;

        /*
         * Clear saved_p to indicate that it's no longer occupying
         * a queue slot on the target queue
         */
        xd->saved_p = false;

        /* Check for more work in the queue */
        xive_do_queue_eoi(xc);
}

/*
 * Helper used to mask and unmask an interrupt source. This
 * is only called for normal interrupts that do not require
 * masking/unmasking via firmware.
 */
static void xive_do_source_set_mask(struct xive_irq_data *xd,
                                    bool mask)
{
        u64 val;

        /*
         * If the interrupt had P set, it may be in a queue.
         *
         * We need to make sure we don't re-enable it until it
         * has been fetched from that queue and EOId. We keep
         * a copy of that P state and use it to restore the
         * ESB accordingly on unmask.
         */
        if (mask) {
                val = xive_esb_read(xd, XIVE_ESB_SET_PQ_01);
                if (!xd->stale_p && !!(val & XIVE_ESB_VAL_P))
                        xd->saved_p = true;
                xd->stale_p = false;
        } else if (xd->saved_p) {
                xive_esb_read(xd, XIVE_ESB_SET_PQ_10);
                xd->saved_p = false;
        } else {
                xive_esb_read(xd, XIVE_ESB_SET_PQ_00);
                xd->stale_p = false;
        }
}

/*
 * Try to chose "cpu" as a new interrupt target. Increments
 * the queue accounting for that target if it's not already
 * full.
 */
static bool xive_try_pick_target(int cpu)
{
        struct xive_cpu *xc = per_cpu(xive_cpu, cpu);
        struct xive_q *q = &xc->queue[xive_irq_priority];
        int max;

        /*
         * Calculate max number of interrupts in that queue.
         *
         * We leave a gap of 1 just in case...
         */
        max = (q->msk + 1) - 1;
        return !!atomic_add_unless(&q->count, 1, max);
}

/*
 * Un-account an interrupt for a target CPU. We don't directly
 * decrement q->count since the interrupt might still be present
 * in the queue.
 *
 * Instead increment a separate counter "pending_count" which
 * will be substracted from "count" later when that CPU observes
 * the queue to be empty.
 */
static void xive_dec_target_count(int cpu)
{
        struct xive_cpu *xc = per_cpu(xive_cpu, cpu);
        struct xive_q *q = &xc->queue[xive_irq_priority];

        if (WARN_ON(cpu < 0 || !xc)) {
                pr_err("%s: cpu=%d xc=%p\n", __func__, cpu, xc);
                return;
        }

        /*
         * We increment the "pending count" which will be used
         * to decrement the target queue count whenever it's next
         * processed and found empty. This ensure that we don't
         * decrement while we still have the interrupt there
         * occupying a slot.
         */
        atomic_inc(&q->pending_count);
}

/* Find a tentative CPU target in a CPU mask */
static int xive_find_target_in_mask(const struct cpumask *mask,
                                    unsigned int fuzz)
{
        int cpu, first, num, i;

        /* Pick up a starting point CPU in the mask based on  fuzz */
        num = min_t(int, cpumask_weight(mask), nr_cpu_ids);
        first = fuzz % num;

        /* Locate it */
        cpu = cpumask_first(mask);
        for (i = 0; i < first && cpu < nr_cpu_ids; i++)
                cpu = cpumask_next(cpu, mask);

        /* Sanity check */
        if (WARN_ON(cpu >= nr_cpu_ids))
                cpu = cpumask_first(cpu_online_mask);

        /* Remember first one to handle wrap-around */
        first = cpu;

        /*
         * Now go through the entire mask until we find a valid
         * target.
         */
        do {
                /*
                 * We re-check online as the fallback case passes us
                 * an untested affinity mask
                 */
                if (cpu_online(cpu) && xive_try_pick_target(cpu))
                        return cpu;
                cpu = cpumask_next(cpu, mask);
                /* Wrap around */
                if (cpu >= nr_cpu_ids)
                        cpu = cpumask_first(mask);
        } while (cpu != first);

        return -1;
}

/*
 * Pick a target CPU for an interrupt. This is done at
 * startup or if the affinity is changed in a way that
 * invalidates the current target.
 */
static int xive_pick_irq_target(struct irq_data *d,
                                const struct cpumask *affinity)
{
        static unsigned int fuzz;
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);
        cpumask_var_t mask;
        int cpu = -1;

        /*
         * If we have chip IDs, first we try to build a mask of
         * CPUs matching the CPU and find a target in there
         */
        if (xd->src_chip != XIVE_INVALID_CHIP_ID &&
                zalloc_cpumask_var(&mask, GFP_ATOMIC)) {
                /* Build a mask of matching chip IDs */
                for_each_cpu_and(cpu, affinity, cpu_online_mask) {
                        struct xive_cpu *xc = per_cpu(xive_cpu, cpu);
                        if (xc->chip_id == xd->src_chip)
                                cpumask_set_cpu(cpu, mask);
                }
                /* Try to find a target */
                if (cpumask_empty(mask))
                        cpu = -1;
                else
                        cpu = xive_find_target_in_mask(mask, fuzz++);
                free_cpumask_var(mask);
                if (cpu >= 0)
                        return cpu;
                fuzz--;
        }

        /* No chip IDs, fallback to using the affinity mask */
        return xive_find_target_in_mask(affinity, fuzz++);
}

static unsigned int xive_irq_startup(struct irq_data *d)
{
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
        int target, rc;

        xd->saved_p = false;
        xd->stale_p = false;
        pr_devel("xive_irq_startup: irq %d [0x%x] data @%p\n",
                 d->irq, hw_irq, d);

#ifdef CONFIG_PCI_MSI
        /*
         * The generic MSI code returns with the interrupt disabled on the
         * card, using the MSI mask bits. Firmware doesn't appear to unmask
         * at that level, so we do it here by hand.
         */
        if (irq_data_get_msi_desc(d))
                pci_msi_unmask_irq(d);
#endif

        /* Pick a target */
        target = xive_pick_irq_target(d, irq_data_get_affinity_mask(d));
        if (target == XIVE_INVALID_TARGET) {
                /* Try again breaking affinity */
                target = xive_pick_irq_target(d, cpu_online_mask);
                if (target == XIVE_INVALID_TARGET)
                        return -ENXIO;
                pr_warn("irq %d started with broken affinity\n", d->irq);
        }

        /* Sanity check */
        if (WARN_ON(target == XIVE_INVALID_TARGET ||
                    target >= nr_cpu_ids))
                target = smp_processor_id();

        xd->target = target;

        /*
         * Configure the logical number to be the Linux IRQ number
         * and set the target queue
         */
        rc = xive_ops->configure_irq(hw_irq,
                                     get_hard_smp_processor_id(target),
                                     xive_irq_priority, d->irq);
        if (rc)
                return rc;

        /* Unmask the ESB */
        xive_do_source_set_mask(xd, false);

        return 0;
}

/* called with irq descriptor lock held */
static void xive_irq_shutdown(struct irq_data *d)
{
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);

        pr_devel("xive_irq_shutdown: irq %d [0x%x] data @%p\n",
                 d->irq, hw_irq, d);

        if (WARN_ON(xd->target == XIVE_INVALID_TARGET))
                return;

        /* Mask the interrupt at the source */
        xive_do_source_set_mask(xd, true);

        /*
         * Mask the interrupt in HW in the IVT/EAS and set the number
         * to be the "bad" IRQ number
         */
        xive_ops->configure_irq(hw_irq,
                                get_hard_smp_processor_id(xd->target),
                                0xff, XIVE_BAD_IRQ);

        xive_dec_target_count(xd->target);
        xd->target = XIVE_INVALID_TARGET;
}

static void xive_irq_unmask(struct irq_data *d)
{
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);

        pr_devel("xive_irq_unmask: irq %d data @%p\n", d->irq, xd);

        /*
         * This is a workaround for PCI LSI problems on P9, for
         * these, we call FW to set the mask. The problems might
         * be fixed by P9 DD2.0, if that is the case, firmware
         * will no longer set that flag.
         */
        if (xd->flags & XIVE_IRQ_FLAG_MASK_FW) {
                unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
                xive_ops->configure_irq(hw_irq,
                                        get_hard_smp_processor_id(xd->target),
                                        xive_irq_priority, d->irq);
                return;
        }

        xive_do_source_set_mask(xd, false);
}

static void xive_irq_mask(struct irq_data *d)
{
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);

        pr_devel("xive_irq_mask: irq %d data @%p\n", d->irq, xd);

        /*
         * This is a workaround for PCI LSI problems on P9, for
         * these, we call OPAL to set the mask. The problems might
         * be fixed by P9 DD2.0, if that is the case, firmware
         * will no longer set that flag.
         */
        if (xd->flags & XIVE_IRQ_FLAG_MASK_FW) {
                unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
                xive_ops->configure_irq(hw_irq,
                                        get_hard_smp_processor_id(xd->target),
                                        0xff, d->irq);
                return;
        }

        xive_do_source_set_mask(xd, true);
}

static int xive_irq_set_affinity(struct irq_data *d,
                                 const struct cpumask *cpumask,
                                 bool force)
{
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
        u32 target, old_target;
        int rc = 0;

        pr_devel("xive_irq_set_affinity: irq %d\n", d->irq);

        /* Is this valid ? */
        if (cpumask_any_and(cpumask, cpu_online_mask) >= nr_cpu_ids)
                return -EINVAL;

        /* Don't do anything if the interrupt isn't started */
        if (!irqd_is_started(d))
                return IRQ_SET_MASK_OK;

        /*
         * If existing target is already in the new mask, and is
         * online then do nothing.
         */
        if (xd->target != XIVE_INVALID_TARGET &&
            cpu_online(xd->target) &&
            cpumask_test_cpu(xd->target, cpumask))
                return IRQ_SET_MASK_OK;

        /* Pick a new target */
        target = xive_pick_irq_target(d, cpumask);

        /* No target found */
        if (target == XIVE_INVALID_TARGET)
                return -ENXIO;

        /* Sanity check */
        if (WARN_ON(target >= nr_cpu_ids))
                target = smp_processor_id();

        old_target = xd->target;

        /*
         * Only configure the irq if it's not currently passed-through to
         * a KVM guest
         */
        if (!irqd_is_forwarded_to_vcpu(d))
                rc = xive_ops->configure_irq(hw_irq,
                                             get_hard_smp_processor_id(target),
                                             xive_irq_priority, d->irq);
        if (rc < 0) {
                pr_err("Error %d reconfiguring irq %d\n", rc, d->irq);
                return rc;
        }

        pr_devel("  target: 0x%x\n", target);
        xd->target = target;

        /* Give up previous target */
        if (old_target != XIVE_INVALID_TARGET)
            xive_dec_target_count(old_target);

        return IRQ_SET_MASK_OK;
}

static int xive_irq_set_type(struct irq_data *d, unsigned int flow_type)
{
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);

        /*
         * We only support these. This has really no effect other than setting
         * the corresponding descriptor bits mind you but those will in turn
         * affect the resend function when re-enabling an edge interrupt.
         *
         * Set set the default to edge as explained in map().
         */
        if (flow_type == IRQ_TYPE_DEFAULT || flow_type == IRQ_TYPE_NONE)
                flow_type = IRQ_TYPE_EDGE_RISING;

        if (flow_type != IRQ_TYPE_EDGE_RISING &&
            flow_type != IRQ_TYPE_LEVEL_LOW)
                return -EINVAL;

        irqd_set_trigger_type(d, flow_type);

        /*
         * Double check it matches what the FW thinks
         *
         * NOTE: We don't know yet if the PAPR interface will provide
         * the LSI vs MSI information apart from the device-tree so
         * this check might have to move into an optional backend call
         * that is specific to the native backend
         */
        if ((flow_type == IRQ_TYPE_LEVEL_LOW) !=
            !!(xd->flags & XIVE_IRQ_FLAG_LSI)) {
                pr_warn("Interrupt %d (HW 0x%x) type mismatch, Linux says %s, FW says %s\n",
                        d->irq, (u32)irqd_to_hwirq(d),
                        (flow_type == IRQ_TYPE_LEVEL_LOW) ? "Level" : "Edge",
                        (xd->flags & XIVE_IRQ_FLAG_LSI) ? "Level" : "Edge");
        }

        return IRQ_SET_MASK_OK_NOCOPY;
}

static int xive_irq_retrigger(struct irq_data *d)
{
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);

        /* This should be only for MSIs */
        if (WARN_ON(xd->flags & XIVE_IRQ_FLAG_LSI))
                return 0;

        /*
         * To perform a retrigger, we first set the PQ bits to
         * 11, then perform an EOI.
         */
        xive_esb_read(xd, XIVE_ESB_SET_PQ_11);

        /*
         * Note: We pass "0" to the hw_irq argument in order to
         * avoid calling into the backend EOI code which we don't
         * want to do in the case of a re-trigger. Backends typically
         * only do EOI for LSIs anyway.
         */
        xive_do_source_eoi(0, xd);

        return 1;
}

/*
 * Caller holds the irq descriptor lock, so this won't be called
 * concurrently with xive_get_irqchip_state on the same interrupt.
 */
static int xive_irq_set_vcpu_affinity(struct irq_data *d, void *state)
{
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(d);
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
        int rc;
        u8 pq;

        /*
         * We only support this on interrupts that do not require
         * firmware calls for masking and unmasking
         */
        if (xd->flags & XIVE_IRQ_FLAG_MASK_FW)
                return -EIO;

        /*
         * This is called by KVM with state non-NULL for enabling
         * pass-through or NULL for disabling it
         */
        if (state) {
                irqd_set_forwarded_to_vcpu(d);

                /* Set it to PQ=10 state to prevent further sends */
                pq = xive_esb_read(xd, XIVE_ESB_SET_PQ_10);
                if (!xd->stale_p) {
                        xd->saved_p = !!(pq & XIVE_ESB_VAL_P);
                        xd->stale_p = !xd->saved_p;
                }

                /* No target ? nothing to do */
                if (xd->target == XIVE_INVALID_TARGET) {
                        /*
                         * An untargetted interrupt should have been
                         * also masked at the source
                         */
                        WARN_ON(xd->saved_p);

                        return 0;
                }

                /*
                 * If P was set, adjust state to PQ=11 to indicate
                 * that a resend is needed for the interrupt to reach
                 * the guest. Also remember the value of P.
                 *
                 * This also tells us that it's in flight to a host queue
                 * or has already been fetched but hasn't been EOIed yet
                 * by the host. This it's potentially using up a host
                 * queue slot. This is important to know because as long
                 * as this is the case, we must not hard-unmask it when
                 * "returning" that interrupt to the host.
                 *
                 * This saved_p is cleared by the host EOI, when we know
                 * for sure the queue slot is no longer in use.
                 */
                if (xd->saved_p) {
                        xive_esb_read(xd, XIVE_ESB_SET_PQ_11);

                        /*
                         * Sync the XIVE source HW to ensure the interrupt
                         * has gone through the EAS before we change its
                         * target to the guest. That should guarantee us
                         * that we *will* eventually get an EOI for it on
                         * the host. Otherwise there would be a small window
                         * for P to be seen here but the interrupt going
                         * to the guest queue.
                         */
                        if (xive_ops->sync_source)
                                xive_ops->sync_source(hw_irq);
                }
        } else {
                irqd_clr_forwarded_to_vcpu(d);

                /* No host target ? hard mask and return */
                if (xd->target == XIVE_INVALID_TARGET) {
                        xive_do_source_set_mask(xd, true);
                        return 0;
                }

                /*
                 * Sync the XIVE source HW to ensure the interrupt
                 * has gone through the EAS before we change its
                 * target to the host.
                 */
                if (xive_ops->sync_source)
                        xive_ops->sync_source(hw_irq);

                /*
                 * By convention we are called with the interrupt in
                 * a PQ=10 or PQ=11 state, ie, it won't fire and will
                 * have latched in Q whether there's a pending HW
                 * interrupt or not.
                 *
                 * First reconfigure the target.
                 */
                rc = xive_ops->configure_irq(hw_irq,
                                             get_hard_smp_processor_id(xd->target),
                                             xive_irq_priority, d->irq);
                if (rc)
                        return rc;

                /*
                 * Then if saved_p is not set, effectively re-enable the
                 * interrupt with an EOI. If it is set, we know there is
                 * still a message in a host queue somewhere that will be
                 * EOId eventually.
                 *
                 * Note: We don't check irqd_irq_disabled(). Effectively,
                 * we *will* let the irq get through even if masked if the
                 * HW is still firing it in order to deal with the whole
                 * saved_p business properly. If the interrupt triggers
                 * while masked, the generic code will re-mask it anyway.
                 */
                if (!xd->saved_p)
                        xive_do_source_eoi(hw_irq, xd);

        }
        return 0;
}

/* Called with irq descriptor lock held. */
static int xive_get_irqchip_state(struct irq_data *data,
                                  enum irqchip_irq_state which, bool *state)
{
        struct xive_irq_data *xd = irq_data_get_irq_handler_data(data);

        switch (which) {
        case IRQCHIP_STATE_ACTIVE:
                *state = !xd->stale_p &&
                         (xd->saved_p ||
                          !!(xive_esb_read(xd, XIVE_ESB_GET) & XIVE_ESB_VAL_P));
                return 0;
        default:
                return -EINVAL;
        }
}

static struct irq_chip xive_irq_chip = {
        .name = "XIVE-IRQ",
        .irq_startup = xive_irq_startup,
        .irq_shutdown = xive_irq_shutdown,
        .irq_eoi = xive_irq_eoi,
        .irq_mask = xive_irq_mask,
        .irq_unmask = xive_irq_unmask,
        .irq_set_affinity = xive_irq_set_affinity,
        .irq_set_type = xive_irq_set_type,
        .irq_retrigger = xive_irq_retrigger,
        .irq_set_vcpu_affinity = xive_irq_set_vcpu_affinity,
        .irq_get_irqchip_state = xive_get_irqchip_state,
};

bool is_xive_irq(struct irq_chip *chip)
{
        return chip == &xive_irq_chip;
}
EXPORT_SYMBOL_GPL(is_xive_irq);

void xive_cleanup_irq_data(struct xive_irq_data *xd)
{
        if (xd->eoi_mmio) {
                iounmap(xd->eoi_mmio);
                if (xd->eoi_mmio == xd->trig_mmio)
                        xd->trig_mmio = NULL;
                xd->eoi_mmio = NULL;
        }
        if (xd->trig_mmio) {
                iounmap(xd->trig_mmio);
                xd->trig_mmio = NULL;
        }
}
EXPORT_SYMBOL_GPL(xive_cleanup_irq_data);

static int xive_irq_alloc_data(unsigned int virq, irq_hw_number_t hw)
{
        struct xive_irq_data *xd;
        int rc;

        xd = kzalloc(sizeof(struct xive_irq_data), GFP_KERNEL);
        if (!xd)
                return -ENOMEM;
        rc = xive_ops->populate_irq_data(hw, xd);
        if (rc) {
                kfree(xd);
                return rc;
        }
        xd->target = XIVE_INVALID_TARGET;
        irq_set_handler_data(virq, xd);

        return 0;
}

static void xive_irq_free_data(unsigned int virq)
{
        struct xive_irq_data *xd = irq_get_handler_data(virq);

        if (!xd)
                return;
        irq_set_handler_data(virq, NULL);
        xive_cleanup_irq_data(xd);
        kfree(xd);
}

#ifdef CONFIG_SMP

static void xive_cause_ipi(int cpu)
{
        struct xive_cpu *xc;
        struct xive_irq_data *xd;

        xc = per_cpu(xive_cpu, cpu);

        DBG_VERBOSE("IPI CPU %d -> %d (HW IRQ 0x%x)\n",
                    smp_processor_id(), cpu, xc->hw_ipi);

        xd = &xc->ipi_data;
        if (WARN_ON(!xd->trig_mmio))
                return;
        out_be64(xd->trig_mmio, 0);
}

static irqreturn_t xive_muxed_ipi_action(int irq, void *dev_id)
{
        return smp_ipi_demux();
}

static void xive_ipi_eoi(struct irq_data *d)
{
        struct xive_cpu *xc = __this_cpu_read(xive_cpu);

        /* Handle possible race with unplug and drop stale IPIs */
        if (!xc)
                return;

        DBG_VERBOSE("IPI eoi: irq=%d [0x%lx] (HW IRQ 0x%x) pending=%02x\n",
                    d->irq, irqd_to_hwirq(d), xc->hw_ipi, xc->pending_prio);

        xive_do_source_eoi(xc->hw_ipi, &xc->ipi_data);
        xive_do_queue_eoi(xc);
}

static void xive_ipi_do_nothing(struct irq_data *d)
{
        /*
         * Nothing to do, we never mask/unmask IPIs, but the callback
         * has to exist for the struct irq_chip.
         */
}

static struct irq_chip xive_ipi_chip = {
        .name = "XIVE-IPI",
        .irq_eoi = xive_ipi_eoi,
        .irq_mask = xive_ipi_do_nothing,
        .irq_unmask = xive_ipi_do_nothing,
};

static void __init xive_request_ipi(void)
{
        unsigned int virq;

        /*
         * Initialization failed, move on, we might manage to
         * reach the point where we display our errors before
         * the system falls appart
         */
        if (!xive_irq_domain)
                return;

        /* Initialize it */
        virq = irq_create_mapping(xive_irq_domain, 0);
        xive_ipi_irq = virq;

        WARN_ON(request_irq(virq, xive_muxed_ipi_action,
                            IRQF_PERCPU | IRQF_NO_THREAD, "IPI", NULL));
}

static int xive_setup_cpu_ipi(unsigned int cpu)
{
        struct xive_cpu *xc;
        int rc;

        pr_debug("Setting up IPI for CPU %d\n", cpu);

        xc = per_cpu(xive_cpu, cpu);

        /* Check if we are already setup */
        if (xc->hw_ipi != 0)
                return 0;

        /* Grab an IPI from the backend, this will populate xc->hw_ipi */
        if (xive_ops->get_ipi(cpu, xc))
                return -EIO;

        /*
         * Populate the IRQ data in the xive_cpu structure and
         * configure the HW / enable the IPIs.
         */
        rc = xive_ops->populate_irq_data(xc->hw_ipi, &xc->ipi_data);
        if (rc) {
                pr_err("Failed to populate IPI data on CPU %d\n", cpu);
                return -EIO;
        }
        rc = xive_ops->configure_irq(xc->hw_ipi,
                                     get_hard_smp_processor_id(cpu),
                                     xive_irq_priority, xive_ipi_irq);
        if (rc) {
                pr_err("Failed to map IPI CPU %d\n", cpu);
                return -EIO;
        }
        pr_devel("CPU %d HW IPI %x, virq %d, trig_mmio=%p\n", cpu,
            xc->hw_ipi, xive_ipi_irq, xc->ipi_data.trig_mmio);

        /* Unmask it */
        xive_do_source_set_mask(&xc->ipi_data, false);

        return 0;
}

static void xive_cleanup_cpu_ipi(unsigned int cpu, struct xive_cpu *xc)
{
        /* Disable the IPI and free the IRQ data */

        /* Already cleaned up ? */
        if (xc->hw_ipi == 0)
                return;

        /* Mask the IPI */
        xive_do_source_set_mask(&xc->ipi_data, true);

        /*
         * Note: We don't call xive_cleanup_irq_data() to free
         * the mappings as this is called from an IPI on kexec
         * which is not a safe environment to call iounmap()
         */

        /* Deconfigure/mask in the backend */
        xive_ops->configure_irq(xc->hw_ipi, hard_smp_processor_id(),
                                0xff, xive_ipi_irq);

        /* Free the IPIs in the backend */
        xive_ops->put_ipi(cpu, xc);
}

void __init xive_smp_probe(void)
{
        smp_ops->cause_ipi = xive_cause_ipi;

        /* Register the IPI */
        xive_request_ipi();

        /* Allocate and setup IPI for the boot CPU */
        xive_setup_cpu_ipi(smp_processor_id());
}

#endif /* CONFIG_SMP */

static int xive_irq_domain_map(struct irq_domain *h, unsigned int virq,
                               irq_hw_number_t hw)
{
        int rc;

        /*
         * Mark interrupts as edge sensitive by default so that resend
         * actually works. Will fix that up below if needed.
         */
        irq_clear_status_flags(virq, IRQ_LEVEL);

#ifdef CONFIG_SMP
        /* IPIs are special and come up with HW number 0 */
        if (hw == 0) {
                /*
                 * IPIs are marked per-cpu. We use separate HW interrupts under
                 * the hood but associated with the same "linux" interrupt
                 */
                irq_set_chip_and_handler(virq, &xive_ipi_chip,
                                         handle_percpu_irq);
                return 0;
        }
#endif

        rc = xive_irq_alloc_data(virq, hw);
        if (rc)
                return rc;

        irq_set_chip_and_handler(virq, &xive_irq_chip, handle_fasteoi_irq);

        return 0;
}

static void xive_irq_domain_unmap(struct irq_domain *d, unsigned int virq)
{
        struct irq_data *data = irq_get_irq_data(virq);
        unsigned int hw_irq;

        /* XXX Assign BAD number */
        if (!data)
                return;
        hw_irq = (unsigned int)irqd_to_hwirq(data);
        if (hw_irq)
                xive_irq_free_data(virq);
}

static int xive_irq_domain_xlate(struct irq_domain *h, struct device_node *ct,
                                 const u32 *intspec, unsigned int intsize,
                                 irq_hw_number_t *out_hwirq, unsigned int *out_flags)

{
        *out_hwirq = intspec[0];

        /*
         * If intsize is at least 2, we look for the type in the second cell,
         * we assume the LSB indicates a level interrupt.
         */
        if (intsize > 1) {
                if (intspec[1] & 1)
                        *out_flags = IRQ_TYPE_LEVEL_LOW;
                else
                        *out_flags = IRQ_TYPE_EDGE_RISING;
        } else
                *out_flags = IRQ_TYPE_LEVEL_LOW;

        return 0;
}

static int xive_irq_domain_match(struct irq_domain *h, struct device_node *node,
                                 enum irq_domain_bus_token bus_token)
{
        return xive_ops->match(node);
}

static const struct irq_domain_ops xive_irq_domain_ops = {
        .match = xive_irq_domain_match,
        .map = xive_irq_domain_map,
        .unmap = xive_irq_domain_unmap,
        .xlate = xive_irq_domain_xlate,
};

static void __init xive_init_host(void)
{
        xive_irq_domain = irq_domain_add_nomap(NULL, XIVE_MAX_IRQ,
                                               &xive_irq_domain_ops, NULL);
        if (WARN_ON(xive_irq_domain == NULL))
                return;
        irq_set_default_host(xive_irq_domain);
}

static void xive_cleanup_cpu_queues(unsigned int cpu, struct xive_cpu *xc)
{
        if (xc->queue[xive_irq_priority].qpage)
                xive_ops->cleanup_queue(cpu, xc, xive_irq_priority);
}

static int xive_setup_cpu_queues(unsigned int cpu, struct xive_cpu *xc)
{
        int rc = 0;

        /* We setup 1 queues for now with a 64k page */
        if (!xc->queue[xive_irq_priority].qpage)
                rc = xive_ops->setup_queue(cpu, xc, xive_irq_priority);

        return rc;
}

static int xive_prepare_cpu(unsigned int cpu)
{
        struct xive_cpu *xc;

        xc = per_cpu(xive_cpu, cpu);
        if (!xc) {
                struct device_node *np;

                xc = kzalloc_node(sizeof(struct xive_cpu),
                                  GFP_KERNEL, cpu_to_node(cpu));
                if (!xc)
                        return -ENOMEM;
                np = of_get_cpu_node(cpu, NULL);
                if (np)
                        xc->chip_id = of_get_ibm_chip_id(np);
                of_node_put(np);

                per_cpu(xive_cpu, cpu) = xc;
        }

        /* Setup EQs if not already */
        return xive_setup_cpu_queues(cpu, xc);
}

static void xive_setup_cpu(void)
{
        struct xive_cpu *xc = __this_cpu_read(xive_cpu);

        /* The backend might have additional things to do */
        if (xive_ops->setup_cpu)
                xive_ops->setup_cpu(smp_processor_id(), xc);

        /* Set CPPR to 0xff to enable flow of interrupts */
        xc->cppr = 0xff;
        out_8(xive_tima + xive_tima_offset + TM_CPPR, 0xff);
}

#ifdef CONFIG_SMP
void xive_smp_setup_cpu(void)
{
        pr_devel("SMP setup CPU %d\n", smp_processor_id());

        /* This will have already been done on the boot CPU */
        if (smp_processor_id() != boot_cpuid)
                xive_setup_cpu();

}

int xive_smp_prepare_cpu(unsigned int cpu)
{
        int rc;

        /* Allocate per-CPU data and queues */
        rc = xive_prepare_cpu(cpu);
        if (rc)
                return rc;

        /* Allocate and setup IPI for the new CPU */
        return xive_setup_cpu_ipi(cpu);
}

#ifdef CONFIG_HOTPLUG_CPU
static void xive_flush_cpu_queue(unsigned int cpu, struct xive_cpu *xc)
{
        u32 irq;

        /* We assume local irqs are disabled */
        WARN_ON(!irqs_disabled());

        /* Check what's already in the CPU queue */
        while ((irq = xive_scan_interrupts(xc, false)) != 0) {
                /*
                 * We need to re-route that interrupt to its new destination.
                 * First get and lock the descriptor
                 */
                struct irq_desc *desc = irq_to_desc(irq);
                struct irq_data *d = irq_desc_get_irq_data(desc);
                struct xive_irq_data *xd;
                unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);

                /*
                 * Ignore anything that isn't a XIVE irq and ignore
                 * IPIs, so can just be dropped.
                 */
                if (d->domain != xive_irq_domain || hw_irq == 0)
                        continue;

                /*
                 * The IRQ should have already been re-routed, it's just a
                 * stale in the old queue, so re-trigger it in order to make
                 * it reach is new destination.
                 */
#ifdef DEBUG_FLUSH
                pr_info("CPU %d: Got irq %d while offline, re-sending...\n",
                        cpu, irq);
#endif
                raw_spin_lock(&desc->lock);
                xd = irq_desc_get_handler_data(desc);

                /*
                 * Clear saved_p to indicate that it's no longer pending
                 */
                xd->saved_p = false;

                /*
                 * For LSIs, we EOI, this will cause a resend if it's
                 * still asserted. Otherwise do an MSI retrigger.
                 */
                if (xd->flags & XIVE_IRQ_FLAG_LSI)
                        xive_do_source_eoi(irqd_to_hwirq(d), xd);
                else
                        xive_irq_retrigger(d);

                raw_spin_unlock(&desc->lock);
        }
}

void xive_smp_disable_cpu(void)
{
        struct xive_cpu *xc = __this_cpu_read(xive_cpu);
        unsigned int cpu = smp_processor_id();

        /* Migrate interrupts away from the CPU */
        irq_migrate_all_off_this_cpu();

        /* Set CPPR to 0 to disable flow of interrupts */
        xc->cppr = 0;
        out_8(xive_tima + xive_tima_offset + TM_CPPR, 0);

        /* Flush everything still in the queue */
        xive_flush_cpu_queue(cpu, xc);

        /* Re-enable CPPR  */
        xc->cppr = 0xff;
        out_8(xive_tima + xive_tima_offset + TM_CPPR, 0xff);
}

void xive_flush_interrupt(void)
{
        struct xive_cpu *xc = __this_cpu_read(xive_cpu);
        unsigned int cpu = smp_processor_id();

        /* Called if an interrupt occurs while the CPU is hot unplugged */
        xive_flush_cpu_queue(cpu, xc);
}

#endif /* CONFIG_HOTPLUG_CPU */

#endif /* CONFIG_SMP */

void xive_teardown_cpu(void)
{
        struct xive_cpu *xc = __this_cpu_read(xive_cpu);
        unsigned int cpu = smp_processor_id();

        /* Set CPPR to 0 to disable flow of interrupts */
        xc->cppr = 0;
        out_8(xive_tima + xive_tima_offset + TM_CPPR, 0);

        if (xive_ops->teardown_cpu)
                xive_ops->teardown_cpu(cpu, xc);

#ifdef CONFIG_SMP
        /* Get rid of IPI */
        xive_cleanup_cpu_ipi(cpu, xc);
#endif

        /* Disable and free the queues */
        xive_cleanup_cpu_queues(cpu, xc);
}

void xive_shutdown(void)
{
        xive_ops->shutdown();
}

bool __init xive_core_init(const struct xive_ops *ops, void __iomem *area, u32 offset,
                           u8 max_prio)
{
        xive_tima = area;
        xive_tima_offset = offset;
        xive_ops = ops;
        xive_irq_priority = max_prio;

        ppc_md.get_irq = xive_get_irq;
        __xive_enabled = true;

        pr_devel("Initializing host..\n");
        xive_init_host();

        pr_devel("Initializing boot CPU..\n");

        /* Allocate per-CPU data and queues */
        xive_prepare_cpu(smp_processor_id());

        /* Get ready for interrupts */
        xive_setup_cpu();

        pr_info("Interrupt handling initialized with %s backend\n",
                xive_ops->name);
        pr_info("Using priority %d for all interrupts\n", max_prio);

        return true;
}

__be32 *xive_queue_page_alloc(unsigned int cpu, u32 queue_shift)
{
        unsigned int alloc_order;
        struct page *pages;
        __be32 *qpage;

        alloc_order = xive_alloc_order(queue_shift);
        pages = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, alloc_order);
        if (!pages)
                return ERR_PTR(-ENOMEM);
        qpage = (__be32 *)page_address(pages);
        memset(qpage, 0, 1 << queue_shift);

        return qpage;
}

static int __init xive_off(char *arg)
{
        xive_cmdline_disabled = true;
        return 0;
}
__setup("xive=off", xive_off);