/* MN10300 Watchdog timer
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 * - Derived from arch/i386/kernel/nmi.c
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
#include <linux/nmi.h>
#include <asm/processor.h>
#include <asm/system.h>
#include <asm/atomic.h>
#include <asm/intctl-regs.h>
#include <asm/rtc-regs.h>
#include <asm/div64.h>
#include <asm/smp.h>
#include <asm/gdb-stub.h>
#include <proc/clock.h>

static DEFINE_SPINLOCK(watchdog_print_lock);
static unsigned int watchdog;
static unsigned int watchdog_hz = 1;
unsigned int watchdog_alert_counter[NR_CPUS];

EXPORT_SYMBOL(touch_nmi_watchdog);

/*
 * the best way to detect whether a CPU has a 'hard lockup' problem
 * is to check its timer makes IRQ counts. If they are not
 * changing then that CPU has some problem.
 *
 * since NMIs dont listen to _any_ locks, we have to be extremely
 * careful not to rely on unsafe variables. The printk might lock
 * up though, so we have to break up any console locks first ...
 * [when there will be more tty-related locks, break them up
 *  here too!]
 */
static unsigned int last_irq_sums[NR_CPUS];

int __init check_watchdog(void)
{
        irq_cpustat_t tmp[1];

        printk(KERN_INFO "Testing Watchdog... ");

        memcpy(tmp, irq_stat, sizeof(tmp));
        local_irq_enable();
        mdelay((10 * 1000) / watchdog_hz); /* wait 10 ticks */
        local_irq_disable();

        if (nmi_count(0) - tmp[0].__nmi_count <= 5) {
                printk(KERN_WARNING "CPU#%d: Watchdog appears to be stuck!\n",
                       0);
                return -1;
        }

        printk(KERN_INFO "OK.\n");

        /* now that we know it works we can reduce NMI frequency to something
         * more reasonable; makes a difference in some configs
         */
        watchdog_hz = 1;

        return 0;
}

static int __init setup_watchdog(char *str)
{
        unsigned tmp;
        int opt;
        u8 ctr;

        get_option(&str, &opt);
        if (opt != 1)
                return 0;

        watchdog = opt;
        if (watchdog) {
                set_intr_stub(EXCEP_WDT, watchdog_handler);
                ctr = WDCTR_WDCK_65536th;
                WDCTR = WDCTR_WDRST | ctr;
                WDCTR = ctr;
                tmp = WDCTR;

                tmp = __muldiv64u(1 << (16 + ctr * 2), 1000000, MN10300_WDCLK);
                tmp = 1000000000 / tmp;
                watchdog_hz = (tmp + 500) / 1000;
        }

        return 1;
}

__setup("watchdog=", setup_watchdog);

void __init watchdog_go(void)
{
        u8 wdt;

        if (watchdog) {
                printk(KERN_INFO "Watchdog: running at %uHz\n", watchdog_hz);
                wdt = WDCTR & ~WDCTR_WDCNE;
                WDCTR = wdt | WDCTR_WDRST;
                wdt = WDCTR;
                WDCTR = wdt | WDCTR_WDCNE;
                wdt = WDCTR;

                check_watchdog();
        }
}

#ifdef CONFIG_SMP
static void watchdog_dump_register(void *dummy)
{
        printk(KERN_ERR "--- Register Dump (CPU%d) ---\n", CPUID);
        show_registers(current_frame());
}
#endif

asmlinkage
void watchdog_interrupt(struct pt_regs *regs, enum exception_code excep)
{
        /*
         * Since current-> is always on the stack, and we always switch
         * the stack NMI-atomically, it's safe to use smp_processor_id().
         */
        int sum, cpu;
        int irq = NMIIRQ;
        u8 wdt, tmp;

        wdt = WDCTR & ~WDCTR_WDCNE;
        WDCTR = wdt;
        tmp = WDCTR;
        NMICR = NMICR_WDIF;

        nmi_count(smp_processor_id())++;
        kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));

        for_each_online_cpu(cpu) {

                sum = irq_stat[cpu].__irq_count;

                if ((last_irq_sums[cpu] == sum)
#if defined(CONFIG_GDBSTUB) && defined(CONFIG_SMP)
                        && !(CHK_GDBSTUB_BUSY()
                             || atomic_read(&cpu_doing_single_step))
#endif
                        ) {
                        /*
                         * Ayiee, looks like this CPU is stuck ...
                         * wait a few IRQs (5 seconds) before doing the oops ...
                         */
                        watchdog_alert_counter[cpu]++;
                        if (watchdog_alert_counter[cpu] == 5 * watchdog_hz) {
                                spin_lock(&watchdog_print_lock);
                                /*
                                 * We are in trouble anyway, lets at least try
                                 * to get a message out.
                                 */
                                bust_spinlocks(1);
                                printk(KERN_ERR
                                       "NMI Watchdog detected LOCKUP on CPU%d,"
                                       " pc %08lx, registers:\n",
                                       cpu, regs->pc);
#ifdef CONFIG_SMP
                                printk(KERN_ERR
                                       "--- Register Dump (CPU%d) ---\n",
                                       CPUID);
#endif
                                show_registers(regs);
#ifdef CONFIG_SMP
                                smp_nmi_call_function(watchdog_dump_register,
                                        NULL, 1);
#endif
                                printk(KERN_NOTICE "console shuts up ...\n");
                                console_silent();
                                spin_unlock(&watchdog_print_lock);
                                bust_spinlocks(0);
#ifdef CONFIG_GDBSTUB
                                if (CHK_GDBSTUB_BUSY_AND_ACTIVE())
                                        gdbstub_exception(regs, excep);
                                else
                                        gdbstub_intercept(regs, excep);
#endif
                                do_exit(SIGSEGV);
                        }
                } else {
                        last_irq_sums[cpu] = sum;
                        watchdog_alert_counter[cpu] = 0;
                }
        }

        WDCTR = wdt | WDCTR_WDRST;
        tmp = WDCTR;
        WDCTR = wdt | WDCTR_WDCNE;
        tmp = WDCTR;
}