// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 2016 IBM Corporation.
 */
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/irq.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/of.h>

#include <asm/smp.h>
#include <asm/irq.h>
#include <asm/errno.h>
#include <asm/xics.h>
#include <asm/io.h>
#include <asm/opal.h>
#include <asm/kvm_ppc.h>

static void icp_opal_teardown_cpu(void)
{
        int hw_cpu = hard_smp_processor_id();

        /* Clear any pending IPI */
        opal_int_set_mfrr(hw_cpu, 0xff);
}

static void icp_opal_flush_ipi(void)
{
        /*
         * We take the ipi irq but and never return so we need to EOI the IPI,
         * but want to leave our priority 0.
         *
         * Should we check all the other interrupts too?
         * Should we be flagging idle loop instead?
         * Or creating some task to be scheduled?
         */
        if (opal_int_eoi((0x00 << 24) | XICS_IPI) > 0)
                force_external_irq_replay();
}

static unsigned int icp_opal_get_xirr(void)
{
        unsigned int kvm_xirr;
        __be32 hw_xirr;
        int64_t rc;

        /* Handle an interrupt latched by KVM first */
        kvm_xirr = kvmppc_get_xics_latch();
        if (kvm_xirr)
                return kvm_xirr;

        /* Then ask OPAL */
        rc = opal_int_get_xirr(&hw_xirr, false);
        if (rc < 0)
                return 0;
        return be32_to_cpu(hw_xirr);
}

static unsigned int icp_opal_get_irq(void)
{
        unsigned int xirr;
        unsigned int vec;
        unsigned int irq;

        xirr = icp_opal_get_xirr();
        vec = xirr & 0x00ffffff;
        if (vec == XICS_IRQ_SPURIOUS)
                return 0;

        irq = irq_find_mapping(xics_host, vec);
        if (likely(irq)) {
                xics_push_cppr(vec);
                return irq;
        }

        /* We don't have a linux mapping, so have rtas mask it. */
        xics_mask_unknown_vec(vec);

        /* We might learn about it later, so EOI it */
        if (opal_int_eoi(xirr) > 0)
                force_external_irq_replay();

        return 0;
}

static void icp_opal_set_cpu_priority(unsigned char cppr)
{
        /*
         * Here be dragons. The caller has asked to allow only IPI's and not
         * external interrupts. But OPAL XIVE doesn't support that. So instead
         * of allowing no interrupts allow all. That's still not right, but
         * currently the only caller who does this is xics_migrate_irqs_away()
         * and it works in that case.
         */
        if (cppr >= DEFAULT_PRIORITY)
                cppr = LOWEST_PRIORITY;

        xics_set_base_cppr(cppr);
        opal_int_set_cppr(cppr);
        iosync();
}

static void icp_opal_eoi(struct irq_data *d)
{
        unsigned int hw_irq = (unsigned int)irqd_to_hwirq(d);
        int64_t rc;

        iosync();
        rc = opal_int_eoi((xics_pop_cppr() << 24) | hw_irq);

        /*
         * EOI tells us whether there are more interrupts to fetch.
         *
         * Some HW implementations might not be able to send us another
         * external interrupt in that case, so we force a replay.
         */
        if (rc > 0)
                force_external_irq_replay();
}

#ifdef CONFIG_SMP

static void icp_opal_cause_ipi(int cpu)
{
        int hw_cpu = get_hard_smp_processor_id(cpu);

        kvmppc_set_host_ipi(cpu, 1);
        opal_int_set_mfrr(hw_cpu, IPI_PRIORITY);
}

static irqreturn_t icp_opal_ipi_action(int irq, void *dev_id)
{
        int cpu = smp_processor_id();

        kvmppc_set_host_ipi(cpu, 0);
        opal_int_set_mfrr(get_hard_smp_processor_id(cpu), 0xff);

        return smp_ipi_demux();
}

/*
 * Called when an interrupt is received on an off-line CPU to
 * clear the interrupt, so that the CPU can go back to nap mode.
 */
void icp_opal_flush_interrupt(void)
{
        unsigned int xirr;
        unsigned int vec;

        do {
                xirr = icp_opal_get_xirr();
                vec = xirr & 0x00ffffff;
                if (vec == XICS_IRQ_SPURIOUS)
                        break;
                if (vec == XICS_IPI) {
                        /* Clear pending IPI */
                        int cpu = smp_processor_id();
                        kvmppc_set_host_ipi(cpu, 0);
                        opal_int_set_mfrr(get_hard_smp_processor_id(cpu), 0xff);
                } else {
                        pr_err("XICS: hw interrupt 0x%x to offline cpu, "
                               "disabling\n", vec);
                        xics_mask_unknown_vec(vec);
                }

                /* EOI the interrupt */
        } while (opal_int_eoi(xirr) > 0);
}

#endif /* CONFIG_SMP */

static const struct icp_ops icp_opal_ops = {
        .get_irq        = icp_opal_get_irq,
        .eoi            = icp_opal_eoi,
        .set_priority   = icp_opal_set_cpu_priority,
        .teardown_cpu   = icp_opal_teardown_cpu,
        .flush_ipi      = icp_opal_flush_ipi,
#ifdef CONFIG_SMP
        .ipi_action     = icp_opal_ipi_action,
        .cause_ipi      = icp_opal_cause_ipi,
#endif
};

int icp_opal_init(void)
{
        struct device_node *np;

        np = of_find_compatible_node(NULL, NULL, "ibm,opal-intc");
        if (!np)
                return -ENODEV;

        icp_ops = &icp_opal_ops;

        printk("XICS: Using OPAL ICP fallbacks\n");

        return 0;
}