/*
 * ACPI probing code for ARM performance counters.
 *
 * Copyright (C) 2017 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/acpi.h>
#include <linux/cpumask.h>
#include <linux/init.h>
#include <linux/irq.h>
#include <linux/irqdesc.h>
#include <linux/percpu.h>
#include <linux/perf/arm_pmu.h>

#include <asm/cputype.h>

static DEFINE_PER_CPU(struct arm_pmu *, probed_pmus);
static DEFINE_PER_CPU(int, pmu_irqs);

static int arm_pmu_acpi_register_irq(int cpu)
{
        struct acpi_madt_generic_interrupt *gicc;
        int gsi, trigger;

        gicc = acpi_cpu_get_madt_gicc(cpu);
        if (WARN_ON(!gicc))
                return -EINVAL;

        gsi = gicc->performance_interrupt;

        /*
         * Per the ACPI spec, the MADT cannot describe a PMU that doesn't
         * have an interrupt. QEMU advertises this by using a GSI of zero,
         * which is not known to be valid on any hardware despite being
         * valid per the spec. Take the pragmatic approach and reject a
         * GSI of zero for now.
         */
        if (!gsi)
                return 0;

        if (gicc->flags & ACPI_MADT_PERFORMANCE_IRQ_MODE)
                trigger = ACPI_EDGE_SENSITIVE;
        else
                trigger = ACPI_LEVEL_SENSITIVE;

        /*
         * Helpfully, the MADT GICC doesn't have a polarity flag for the
         * "performance interrupt". Luckily, on compliant GICs the polarity is
         * a fixed value in HW (for both SPIs and PPIs) that we cannot change
         * from SW.
         *
         * Here we pass in ACPI_ACTIVE_HIGH to keep the core code happy. This
         * may not match the real polarity, but that should not matter.
         *
         * Other interrupt controllers are not supported with ACPI.
         */
        return acpi_register_gsi(NULL, gsi, trigger, ACPI_ACTIVE_HIGH);
}

static void arm_pmu_acpi_unregister_irq(int cpu)
{
        struct acpi_madt_generic_interrupt *gicc;
        int gsi;

        gicc = acpi_cpu_get_madt_gicc(cpu);
        if (!gicc)
                return;

        gsi = gicc->performance_interrupt;
        acpi_unregister_gsi(gsi);
}

static int arm_pmu_acpi_parse_irqs(void)
{
        int irq, cpu, irq_cpu, err;

        for_each_possible_cpu(cpu) {
                irq = arm_pmu_acpi_register_irq(cpu);
                if (irq < 0) {
                        err = irq;
                        pr_warn("Unable to parse ACPI PMU IRQ for CPU%d: %d\n",
                                cpu, err);
                        goto out_err;
                } else if (irq == 0) {
                        pr_warn("No ACPI PMU IRQ for CPU%d\n", cpu);
                }

                /*
                 * Log and request the IRQ so the core arm_pmu code can manage
                 * it. We'll have to sanity-check IRQs later when we associate
                 * them with their PMUs.
                 */
                per_cpu(pmu_irqs, cpu) = irq;
                armpmu_request_irq(irq, cpu);
        }

        return 0;

out_err:
        for_each_possible_cpu(cpu) {
                irq = per_cpu(pmu_irqs, cpu);
                if (!irq)
                        continue;

                arm_pmu_acpi_unregister_irq(cpu);

                /*
                 * Blat all copies of the IRQ so that we only unregister the
                 * corresponding GSI once (e.g. when we have PPIs).
                 */
                for_each_possible_cpu(irq_cpu) {
                        if (per_cpu(pmu_irqs, irq_cpu) == irq)
                                per_cpu(pmu_irqs, irq_cpu) = 0;
                }
        }

        return err;
}

static struct arm_pmu *arm_pmu_acpi_find_alloc_pmu(void)
{
        unsigned long cpuid = read_cpuid_id();
        struct arm_pmu *pmu;
        int cpu;

        for_each_possible_cpu(cpu) {
                pmu = per_cpu(probed_pmus, cpu);
                if (!pmu || pmu->acpi_cpuid != cpuid)
                        continue;

                return pmu;
        }

        pmu = armpmu_alloc_atomic();
        if (!pmu) {
                pr_warn("Unable to allocate PMU for CPU%d\n",
                        smp_processor_id());
                return NULL;
        }

        pmu->acpi_cpuid = cpuid;

        return pmu;
}

/*
 * Check whether the new IRQ is compatible with those already associated with
 * the PMU (e.g. we don't have mismatched PPIs).
 */
static bool pmu_irq_matches(struct arm_pmu *pmu, int irq)
{
        struct pmu_hw_events __percpu *hw_events = pmu->hw_events;
        int cpu;

        if (!irq)
                return true;

        for_each_cpu(cpu, &pmu->supported_cpus) {
                int other_irq = per_cpu(hw_events->irq, cpu);
                if (!other_irq)
                        continue;

                if (irq == other_irq)
                        continue;
                if (!irq_is_percpu_devid(irq) && !irq_is_percpu_devid(other_irq))
                        continue;

                pr_warn("mismatched PPIs detected\n");
                return false;
        }

        return true;
}

/*
 * This must run before the common arm_pmu hotplug logic, so that we can
 * associate a CPU and its interrupt before the common code tries to manage the
 * affinity and so on.
 *
 * Note that hotplug events are serialized, so we cannot race with another CPU
 * coming up. The perf core won't open events while a hotplug event is in
 * progress.
 */
static int arm_pmu_acpi_cpu_starting(unsigned int cpu)
{
        struct arm_pmu *pmu;
        struct pmu_hw_events __percpu *hw_events;
        int irq;

        /* If we've already probed this CPU, we have nothing to do */
        if (per_cpu(probed_pmus, cpu))
                return 0;

        irq = per_cpu(pmu_irqs, cpu);

        pmu = arm_pmu_acpi_find_alloc_pmu();
        if (!pmu)
                return -ENOMEM;

        per_cpu(probed_pmus, cpu) = pmu;

        if (pmu_irq_matches(pmu, irq)) {
                hw_events = pmu->hw_events;
                per_cpu(hw_events->irq, cpu) = irq;
        }

        cpumask_set_cpu(cpu, &pmu->supported_cpus);

        /*
         * Ideally, we'd probe the PMU here when we find the first matching
         * CPU. We can't do that for several reasons; see the comment in
         * arm_pmu_acpi_init().
         *
         * So for the time being, we're done.
         */
        return 0;
}

int arm_pmu_acpi_probe(armpmu_init_fn init_fn)
{
        int pmu_idx = 0;
        int cpu, ret;

        /*
         * Initialise and register the set of PMUs which we know about right
         * now. Ideally we'd do this in arm_pmu_acpi_cpu_starting() so that we
         * could handle late hotplug, but this may lead to deadlock since we
         * might try to register a hotplug notifier instance from within a
         * hotplug notifier.
         *
         * There's also the problem of having access to the right init_fn,
         * without tying this too deeply into the "real" PMU driver.
         *
         * For the moment, as with the platform/DT case, we need at least one
         * of a PMU's CPUs to be online at probe time.
         */
        for_each_possible_cpu(cpu) {
                struct arm_pmu *pmu = per_cpu(probed_pmus, cpu);
                char *base_name;

                if (!pmu || pmu->name)
                        continue;

                ret = init_fn(pmu);
                if (ret == -ENODEV) {
                        /* PMU not handled by this driver, or not present */
                        continue;
                } else if (ret) {
                        pr_warn("Unable to initialise PMU for CPU%d\n", cpu);
                        return ret;
                }

                base_name = pmu->name;
                pmu->name = kasprintf(GFP_KERNEL, "%s_%d", base_name, pmu_idx++);
                if (!pmu->name) {
                        pr_warn("Unable to allocate PMU name for CPU%d\n", cpu);
                        return -ENOMEM;
                }

                ret = armpmu_register(pmu);
                if (ret) {
                        pr_warn("Failed to register PMU for CPU%d\n", cpu);
                        kfree(pmu->name);
                        return ret;
                }
        }

        return 0;
}

static int arm_pmu_acpi_init(void)
{
        int ret;

        if (acpi_disabled)
                return 0;

        ret = arm_pmu_acpi_parse_irqs();
        if (ret)
                return ret;

        ret = cpuhp_setup_state(CPUHP_AP_PERF_ARM_ACPI_STARTING,
                                "perf/arm/pmu_acpi:starting",
                                arm_pmu_acpi_cpu_starting, NULL);

        return ret;
}
subsys_initcall(arm_pmu_acpi_init)