/* Pseudo NMI support on sparc64 systems.
 *
 * Copyright (C) 2009 David S. Miller <davem@davemloft.net>
 *
 * The NMI watchdog support and infrastructure is based almost
 * entirely upon the x86 NMI support code.
 */
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/init.h>
#include <linux/percpu.h>
#include <linux/nmi.h>
#include <linux/export.h>
#include <linux/kprobes.h>
#include <linux/kernel_stat.h>
#include <linux/reboot.h>
#include <linux/slab.h>
#include <linux/kdebug.h>
#include <linux/delay.h>
#include <linux/smp.h>

#include <asm/perf_event.h>
#include <asm/ptrace.h>
#include <asm/pcr.h>

#include "kstack.h"

/* We don't have a real NMI on sparc64, but we can fake one
 * up using profiling counter overflow interrupts and interrupt
 * levels.
 *
 * The profile overflow interrupts at level 15, so we use
 * level 14 as our IRQ off level.
 */

static int panic_on_timeout;

/* nmi_active:
 * >0: the NMI watchdog is active, but can be disabled
 * <0: the NMI watchdog has not been set up, and cannot be enabled
 *  0: the NMI watchdog is disabled, but can be enabled
 */
atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
EXPORT_SYMBOL(nmi_active);
static int nmi_init_done;
static unsigned int nmi_hz = HZ;
static DEFINE_PER_CPU(short, wd_enabled);
static int endflag __initdata;

static DEFINE_PER_CPU(unsigned int, last_irq_sum);
static DEFINE_PER_CPU(long, alert_counter);
static DEFINE_PER_CPU(int, nmi_touch);

void arch_touch_nmi_watchdog(void)
{
        if (atomic_read(&nmi_active)) {
                int cpu;

                for_each_present_cpu(cpu) {
                        if (per_cpu(nmi_touch, cpu) != 1)
                                per_cpu(nmi_touch, cpu) = 1;
                }
        }
}
EXPORT_SYMBOL(arch_touch_nmi_watchdog);

static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
{
        int this_cpu = smp_processor_id();

        if (notify_die(DIE_NMIWATCHDOG, str, regs, 0,
                       pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
                return;

        if (do_panic || panic_on_oops)
                panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
        else
                WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
}

notrace __kprobes void perfctr_irq(int irq, struct pt_regs *regs)
{
        unsigned int sum, touched = 0;
        void *orig_sp;

        clear_softint(1 << irq);

        local_cpu_data().__nmi_count++;

        nmi_enter();

        orig_sp = set_hardirq_stack();

        if (notify_die(DIE_NMI, "nmi", regs, 0,
                       pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
                touched = 1;
        else
                pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);

        sum = local_cpu_data().irq0_irqs;
        if (__this_cpu_read(nmi_touch)) {
                __this_cpu_write(nmi_touch, 0);
                touched = 1;
        }
        if (!touched && __this_cpu_read(last_irq_sum) == sum) {
                __this_cpu_inc(alert_counter);
                if (__this_cpu_read(alert_counter) == 30 * nmi_hz)
                        die_nmi("BUG: NMI Watchdog detected LOCKUP",
                                regs, panic_on_timeout);
        } else {
                __this_cpu_write(last_irq_sum, sum);
                __this_cpu_write(alert_counter, 0);
        }
        if (__this_cpu_read(wd_enabled)) {
                pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
                pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
        }

        restore_hardirq_stack(orig_sp);

        nmi_exit();
}

static inline unsigned int get_nmi_count(int cpu)
{
        return cpu_data(cpu).__nmi_count;
}

static __init void nmi_cpu_busy(void *data)
{
        while (endflag == 0)
                mb();
}

static void report_broken_nmi(int cpu, int *prev_nmi_count)
{
        printk(KERN_CONT "\n");

        printk(KERN_WARNING
                "WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
                        cpu, prev_nmi_count[cpu], get_nmi_count(cpu));

        printk(KERN_WARNING
                "Please report this to bugzilla.kernel.org,\n");
        printk(KERN_WARNING
                "and attach the output of the 'dmesg' command.\n");

        per_cpu(wd_enabled, cpu) = 0;
        atomic_dec(&nmi_active);
}

void stop_nmi_watchdog(void *unused)
{
        if (!__this_cpu_read(wd_enabled))
                return;
        pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
        __this_cpu_write(wd_enabled, 0);
        atomic_dec(&nmi_active);
}

static int __init check_nmi_watchdog(void)
{
        unsigned int *prev_nmi_count;
        int cpu, err;

        if (!atomic_read(&nmi_active))
                return 0;

        prev_nmi_count = kmalloc_array(nr_cpu_ids, sizeof(unsigned int),
                                       GFP_KERNEL);
        if (!prev_nmi_count) {
                err = -ENOMEM;
                goto error;
        }

        printk(KERN_INFO "Testing NMI watchdog ... ");

        smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);

        for_each_possible_cpu(cpu)
                prev_nmi_count[cpu] = get_nmi_count(cpu);
        local_irq_enable();
        mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */

        for_each_online_cpu(cpu) {
                if (!per_cpu(wd_enabled, cpu))
                        continue;
                if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
                        report_broken_nmi(cpu, prev_nmi_count);
        }
        endflag = 1;
        if (!atomic_read(&nmi_active)) {
                kfree(prev_nmi_count);
                atomic_set(&nmi_active, -1);
                err = -ENODEV;
                goto error;
        }
        printk("OK.\n");

        nmi_hz = 1;

        kfree(prev_nmi_count);
        return 0;
error:
        on_each_cpu(stop_nmi_watchdog, NULL, 1);
        return err;
}

void start_nmi_watchdog(void *unused)
{
        if (__this_cpu_read(wd_enabled))
                return;

        __this_cpu_write(wd_enabled, 1);
        atomic_inc(&nmi_active);

        pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
        pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));

        pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
}

static void nmi_adjust_hz_one(void *unused)
{
        if (!__this_cpu_read(wd_enabled))
                return;

        pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
        pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));

        pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
}

void nmi_adjust_hz(unsigned int new_hz)
{
        nmi_hz = new_hz;
        on_each_cpu(nmi_adjust_hz_one, NULL, 1);
}
EXPORT_SYMBOL_GPL(nmi_adjust_hz);

static int nmi_shutdown(struct notifier_block *nb, unsigned long cmd, void *p)
{
        on_each_cpu(stop_nmi_watchdog, NULL, 1);
        return 0;
}

static struct notifier_block nmi_reboot_notifier = {
        .notifier_call = nmi_shutdown,
};

int __init nmi_init(void)
{
        int err;

        on_each_cpu(start_nmi_watchdog, NULL, 1);

        err = check_nmi_watchdog();
        if (!err) {
                err = register_reboot_notifier(&nmi_reboot_notifier);
                if (err) {
                        on_each_cpu(stop_nmi_watchdog, NULL, 1);
                        atomic_set(&nmi_active, -1);
                }
        }

        nmi_init_done = 1;

        return err;
}

static int __init setup_nmi_watchdog(char *str)
{
        if (!strncmp(str, "panic", 5))
                panic_on_timeout = 1;

        return 0;
}
__setup("nmi_watchdog=", setup_nmi_watchdog);

/*
 * sparc specific NMI watchdog enable function.
 * Enables watchdog if it is not enabled already.
 */
int watchdog_nmi_enable(unsigned int cpu)
{
        if (atomic_read(&nmi_active) == -1) {
                pr_warn("NMI watchdog cannot be enabled or disabled\n");
                return -1;
        }

        /*
         * watchdog thread could start even before nmi_init is called.
         * Just Return in that case. Let nmi_init finish the init
         * process first.
         */
        if (!nmi_init_done)
                return 0;

        smp_call_function_single(cpu, start_nmi_watchdog, NULL, 1);

        return 0;
}
/*
 * sparc specific NMI watchdog disable function.
 * Disables watchdog if it is not disabled already.
 */
void watchdog_nmi_disable(unsigned int cpu)
{
        if (atomic_read(&nmi_active) == -1)
                pr_warn_once("NMI watchdog cannot be enabled or disabled\n");
        else
                smp_call_function_single(cpu, stop_nmi_watchdog, NULL, 1);
}