arch/mn10300/kernel/mn10300-watchdog.c

   1 /* MN10300 Watchdog timer
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  * - Derived from arch/i386/kernel/nmi.c
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public Licence
   9  * as published by the Free Software Foundation; either version
  10  * 2 of the Licence, or (at your option) any later version.
  11  */
  12 #include <linux/module.h>
  13 #include <linux/sched.h>
  14 #include <linux/kernel.h>
  15 #include <linux/init.h>
  16 #include <linux/delay.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/kernel_stat.h>
  19 #include <linux/nmi.h>
  20 #include <asm/processor.h>
  21 #include <asm/system.h>
  22 #include <asm/atomic.h>
  23 #include <asm/intctl-regs.h>
  24 #include <asm/rtc-regs.h>
  25 #include <asm/div64.h>
  26 #include <asm/smp.h>
  27 #include <asm/gdb-stub.h>
  28 #include <proc/clock.h>
  29
  30 static DEFINE_SPINLOCK(watchdog_print_lock);
  31 static unsigned int watchdog;
  32 static unsigned int watchdog_hz = 1;
  33 unsigned int watchdog_alert_counter;
  34
  35 EXPORT_SYMBOL(touch_nmi_watchdog);
  36
  37 /*
  38  * the best way to detect whether a CPU has a 'hard lockup' problem
  39  * is to check its timer makes IRQ counts. If they are not
  40  * changing then that CPU has some problem.
  41  *
  42  * as these watchdog NMI IRQs are generated on every CPU, we only
  43  * have to check the current processor.
  44  *
  45  * since NMIs dont listen to _any_ locks, we have to be extremely
  46  * careful not to rely on unsafe variables. The printk might lock
  47  * up though, so we have to break up any console locks first ...
  48  * [when there will be more tty-related locks, break them up
  49  *  here too!]
  50  */
  51 static unsigned int last_irq_sums[NR_CPUS];
  52
  53 int __init check_watchdog(void)
  54 {
  55         irq_cpustat_t tmp[1];
  56
  57         printk(KERN_INFO "Testing Watchdog... ");
  58
  59         memcpy(tmp, irq_stat, sizeof(tmp));
  60         local_irq_enable();
  61         mdelay((10 * 1000) / watchdog_hz); /* wait 10 ticks */
  62         local_irq_disable();
  63
  64         if (nmi_count(0) - tmp[0].__nmi_count <= 5) {
  65                 printk(KERN_WARNING "CPU#%d: Watchdog appears to be stuck!\n",
  66                        0);
  67                 return -1;
  68         }
  69
  70         printk(KERN_INFO "OK.\n");
  71
  72         /* now that we know it works we can reduce NMI frequency to
  73          * something more reasonable; makes a difference in some configs
  74          */
  75         watchdog_hz = 1;
  76
  77         return 0;
  78 }
  79
  80 static int __init setup_watchdog(char *str)
  81 {
  82         unsigned tmp;
  83         int opt;
  84         u8 ctr;
  85
  86         get_option(&str, &opt);
  87         if (opt != 1)
  88                 return 0;
  89
  90         watchdog = opt;
  91         if (watchdog) {
  92                 set_intr_stub(EXCEP_WDT, watchdog_handler);
  93                 ctr = WDCTR_WDCK_65536th;
  94                 WDCTR = WDCTR_WDRST | ctr;
  95                 WDCTR = ctr;
  96                 tmp = WDCTR;
  97
  98                 tmp = __muldiv64u(1 << (16 + ctr * 2), 1000000, MN10300_WDCLK);
  99                 tmp = 1000000000 / tmp;
 100                 watchdog_hz = (tmp + 500) / 1000;
 101         }
 102
 103         return 1;
 104 }
 105
 106 __setup("watchdog=", setup_watchdog);
 107
 108 void __init watchdog_go(void)
 109 {
 110         u8 wdt;
 111
 112         if (watchdog) {
 113                 printk(KERN_INFO "Watchdog: running at %uHz\n", watchdog_hz);
 114                 wdt = WDCTR & ~WDCTR_WDCNE;
 115                 WDCTR = wdt | WDCTR_WDRST;
 116                 wdt = WDCTR;
 117                 WDCTR = wdt | WDCTR_WDCNE;
 118                 wdt = WDCTR;
 119
 120                 check_watchdog();
 121         }
 122 }
 123
 124 asmlinkage
 125 void watchdog_interrupt(struct pt_regs *regs, enum exception_code excep)
 126 {
 127
 128         /*
 129          * Since current-> is always on the stack, and we always switch
 130          * the stack NMI-atomically, it's safe to use smp_processor_id().
 131          */
 132         int sum, cpu = smp_processor_id();
 133         int irq = NMIIRQ;
 134         u8 wdt, tmp;
 135
 136         wdt = WDCTR & ~WDCTR_WDCNE;
 137         WDCTR = wdt;
 138         tmp = WDCTR;
 139         NMICR = NMICR_WDIF;
 140
 141         nmi_count(cpu)++;
 142         kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));
 143         sum = irq_stat[cpu].__irq_count;
 144
 145         if (last_irq_sums[cpu] == sum) {
 146                 /*
 147                  * Ayiee, looks like this CPU is stuck ...
 148                  * wait a few IRQs (5 seconds) before doing the oops ...
 149                  */
 150                 watchdog_alert_counter++;
 151                 if (watchdog_alert_counter == 5 * watchdog_hz) {
 152                         spin_lock(&watchdog_print_lock);
 153                         /*
 154                          * We are in trouble anyway, lets at least try
 155                          * to get a message out.
 156                          */
 157                         bust_spinlocks(1);
 158                         printk(KERN_ERR
 159                                "NMI Watchdog detected LOCKUP on CPU%d,"
 160                                " pc %08lx, registers:\n",
 161                                cpu, regs->pc);
 162                         show_registers(regs);
 163                         printk("console shuts up ...\n");
 164                         console_silent();
 165                         spin_unlock(&watchdog_print_lock);
 166                         bust_spinlocks(0);
 167 #ifdef CONFIG_GDBSTUB
 168                         if (gdbstub_busy)
 169                                 gdbstub_exception(regs, excep);
 170                         else
 171                                 gdbstub_intercept(regs, excep);
 172 #endif
 173                         do_exit(SIGSEGV);
 174                 }
 175         } else {
 176                 last_irq_sums[cpu] = sum;
 177                 watchdog_alert_counter = 0;
 178         }
 179
 180         WDCTR = wdt | WDCTR_WDRST;
 181         tmp = WDCTR;
 182         WDCTR = wdt | WDCTR_WDCNE;
 183         tmp = WDCTR;
 184 }