arch/s390/kernel/time.c

   1 /*
   2  *  arch/s390/kernel/time.c
   3  *    Time of day based timer functions.
   4  *
   5  *  S390 version
   6  *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
   7  *    Author(s): Hartmut Penner (hp@de.ibm.com),
   8  *               Martin Schwidefsky (schwidefsky@de.ibm.com),
   9  *               Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
  10  *
  11  *  Derived from "arch/i386/kernel/time.c"
  12  *    Copyright (C) 1991, 1992, 1995  Linus Torvalds
  13  */
  14
  15 #include <linux/errno.h>
  16 #include <linux/module.h>
  17 #include <linux/sched.h>
  18 #include <linux/kernel.h>
  19 #include <linux/param.h>
  20 #include <linux/string.h>
  21 #include <linux/mm.h>
  22 #include <linux/interrupt.h>
  23 #include <linux/time.h>
  24 #include <linux/delay.h>
  25 #include <linux/init.h>
  26 #include <linux/smp.h>
  27 #include <linux/types.h>
  28 #include <linux/profile.h>
  29 #include <linux/timex.h>
  30 #include <linux/notifier.h>
  31 #include <linux/clocksource.h>
  32
  33 #include <asm/uaccess.h>
  34 #include <asm/delay.h>
  35 #include <asm/s390_ext.h>
  36 #include <asm/div64.h>
  37 #include <asm/irq.h>
  38 #include <asm/irq_regs.h>
  39 #include <asm/timer.h>
  40
  41 /* change this if you have some constant time drift */
  42 #define USECS_PER_JIFFY     ((unsigned long) 1000000/HZ)
  43 #define CLK_TICKS_PER_JIFFY ((unsigned long) USECS_PER_JIFFY << 12)
  44
  45 /*
  46  * Create a small time difference between the timer interrupts
  47  * on the different cpus to avoid lock contention.
  48  */
  49 #define CPU_DEVIATION       (smp_processor_id() << 12)
  50
  51 #define TICK_SIZE tick
  52
  53 static ext_int_info_t ext_int_info_cc;
  54 static u64 init_timer_cc;
  55 static u64 jiffies_timer_cc;
  56 static u64 xtime_cc;
  57
  58 /*
  59  * Scheduler clock - returns current time in nanosec units.
  60  */
  61 unsigned long long sched_clock(void)
  62 {
  63         return ((get_clock() - jiffies_timer_cc) * 125) >> 9;
  64 }
  65
  66 /*
  67  * Monotonic_clock - returns # of nanoseconds passed since time_init()
  68  */
  69 unsigned long long monotonic_clock(void)
  70 {
  71         return sched_clock();
  72 }
  73 EXPORT_SYMBOL(monotonic_clock);
  74
  75 void tod_to_timeval(__u64 todval, struct timespec *xtime)
  76 {
  77         unsigned long long sec;
  78
  79         sec = todval >> 12;
  80         do_div(sec, 1000000);
  81         xtime->tv_sec = sec;
  82         todval -= (sec * 1000000) << 12;
  83         xtime->tv_nsec = ((todval * 1000) >> 12);
  84 }
  85
  86 #ifdef CONFIG_PROFILING
  87 #define s390_do_profile()       profile_tick(CPU_PROFILING)
  88 #else
  89 #define s390_do_profile()       do { ; } while(0)
  90 #endif /* CONFIG_PROFILING */
  91
  92
  93 /*
  94  * timer_interrupt() needs to keep up the real-time clock,
  95  * as well as call the "do_timer()" routine every clocktick
  96  */
  97 void account_ticks(void)
  98 {
  99         __u64 tmp;
 100         __u32 ticks;
 101
 102         /* Calculate how many ticks have passed. */
 103         if (S390_lowcore.int_clock < S390_lowcore.jiffy_timer) {
 104                 /*
 105                  * We have to program the clock comparator even if
 106                  * no tick has passed. That happens if e.g. an i/o
 107                  * interrupt wakes up an idle processor that has
 108                  * switched off its hz timer.
 109                  */
 110                 tmp = S390_lowcore.jiffy_timer + CPU_DEVIATION;
 111                 asm volatile ("SCKC %0" : : "m" (tmp));
 112                 return;
 113         }
 114         tmp = S390_lowcore.int_clock - S390_lowcore.jiffy_timer;
 115         if (tmp >= 2*CLK_TICKS_PER_JIFFY) {  /* more than two ticks ? */
 116                 ticks = __div(tmp, CLK_TICKS_PER_JIFFY) + 1;
 117                 S390_lowcore.jiffy_timer +=
 118                         CLK_TICKS_PER_JIFFY * (__u64) ticks;
 119         } else if (tmp >= CLK_TICKS_PER_JIFFY) {
 120                 ticks = 2;
 121                 S390_lowcore.jiffy_timer += 2*CLK_TICKS_PER_JIFFY;
 122         } else {
 123                 ticks = 1;
 124                 S390_lowcore.jiffy_timer += CLK_TICKS_PER_JIFFY;
 125         }
 126
 127         /* set clock comparator for next tick */
 128         tmp = S390_lowcore.jiffy_timer + CPU_DEVIATION;
 129         asm volatile ("SCKC %0" : : "m" (tmp));
 130
 131 #ifdef CONFIG_SMP
 132         /*
 133          * Do not rely on the boot cpu to do the calls to do_timer.
 134          * Spread it over all cpus instead.
 135          */
 136         write_seqlock(&xtime_lock);
 137         if (S390_lowcore.jiffy_timer > xtime_cc) {
 138                 __u32 xticks;
 139                 tmp = S390_lowcore.jiffy_timer - xtime_cc;
 140                 if (tmp >= 2*CLK_TICKS_PER_JIFFY) {
 141                         xticks = __div(tmp, CLK_TICKS_PER_JIFFY);
 142                         xtime_cc += (__u64) xticks * CLK_TICKS_PER_JIFFY;
 143                 } else {
 144                         xticks = 1;
 145                         xtime_cc += CLK_TICKS_PER_JIFFY;
 146                 }
 147                 do_timer(xticks);
 148         }
 149         write_sequnlock(&xtime_lock);
 150 #else
 151         do_timer(ticks);
 152 #endif
 153
 154 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
 155         account_tick_vtime(current);
 156 #else
 157         while (ticks--)
 158                 update_process_times(user_mode(get_irq_regs()));
 159 #endif
 160
 161         s390_do_profile();
 162 }
 163
 164 #ifdef CONFIG_NO_IDLE_HZ
 165
 166 #ifdef CONFIG_NO_IDLE_HZ_INIT
 167 int sysctl_hz_timer = 0;
 168 #else
 169 int sysctl_hz_timer = 1;
 170 #endif
 171
 172 /*
 173  * Stop the HZ tick on the current CPU.
 174  * Only cpu_idle may call this function.
 175  */
 176 static inline void stop_hz_timer(void)
 177 {
 178         unsigned long flags;
 179         unsigned long seq, next;
 180         __u64 timer, todval;
 181         int cpu = smp_processor_id();
 182
 183         if (sysctl_hz_timer != 0)
 184                 return;
 185
 186         cpu_set(cpu, nohz_cpu_mask);
 187
 188         /*
 189          * Leave the clock comparator set up for the next timer
 190          * tick if either rcu or a softirq is pending.
 191          */
 192         if (rcu_needs_cpu(cpu) || local_softirq_pending()) {
 193                 cpu_clear(cpu, nohz_cpu_mask);
 194                 return;
 195         }
 196
 197         /*
 198          * This cpu is going really idle. Set up the clock comparator
 199          * for the next event.
 200          */
 201         next = next_timer_interrupt();
 202         do {
 203                 seq = read_seqbegin_irqsave(&xtime_lock, flags);
 204                 timer = ((__u64) next) - ((__u64) jiffies) + jiffies_64;
 205         } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
 206         todval = -1ULL;
 207         /* Be careful about overflows. */
 208         if (timer < (-1ULL / CLK_TICKS_PER_JIFFY)) {
 209                 timer = jiffies_timer_cc + timer * CLK_TICKS_PER_JIFFY;
 210                 if (timer >= jiffies_timer_cc)
 211                         todval = timer;
 212         }
 213         asm volatile ("SCKC %0" : : "m" (todval));
 214 }
 215
 216 /*
 217  * Start the HZ tick on the current CPU.
 218  * Only cpu_idle may call this function.
 219  */
 220 static inline void start_hz_timer(void)
 221 {
 222         BUG_ON(!in_interrupt());
 223
 224         if (!cpu_isset(smp_processor_id(), nohz_cpu_mask))
 225                 return;
 226         account_ticks();
 227         cpu_clear(smp_processor_id(), nohz_cpu_mask);
 228 }
 229
 230 static int nohz_idle_notify(struct notifier_block *self,
 231                             unsigned long action, void *hcpu)
 232 {
 233         switch (action) {
 234         case CPU_IDLE:
 235                 stop_hz_timer();
 236                 break;
 237         case CPU_NOT_IDLE:
 238                 start_hz_timer();
 239                 break;
 240         }
 241         return NOTIFY_OK;
 242 }
 243
 244 static struct notifier_block nohz_idle_nb = {
 245         .notifier_call = nohz_idle_notify,
 246 };
 247
 248 static void __init nohz_init(void)
 249 {
 250         if (register_idle_notifier(&nohz_idle_nb))
 251                 panic("Couldn't register idle notifier");
 252 }
 253
 254 #endif
 255
 256 /*
 257  * Start the clock comparator on the current CPU.
 258  */
 259 void init_cpu_timer(void)
 260 {
 261         unsigned long cr0;
 262         __u64 timer;
 263
 264         timer = jiffies_timer_cc + jiffies_64 * CLK_TICKS_PER_JIFFY;
 265         S390_lowcore.jiffy_timer = timer + CLK_TICKS_PER_JIFFY;
 266         timer += CLK_TICKS_PER_JIFFY + CPU_DEVIATION;
 267         asm volatile ("SCKC %0" : : "m" (timer));
 268         /* allow clock comparator timer interrupt */
 269         __ctl_store(cr0, 0, 0);
 270         cr0 |= 0x800;
 271         __ctl_load(cr0, 0, 0);
 272 }
 273
 274 static cycle_t read_tod_clock(void)
 275 {
 276         return get_clock();
 277 }
 278
 279 static struct clocksource clocksource_tod = {
 280         .name           = "tod",
 281         .rating         = 100,
 282         .read           = read_tod_clock,
 283         .mask           = -1ULL,
 284         .mult           = 1000,
 285         .shift          = 12,
 286         .is_continuous  = 1,
 287 };
 288
 289
 290 /*
 291  * Initialize the TOD clock and the CPU timer of
 292  * the boot cpu.
 293  */
 294 void __init time_init(void)
 295 {
 296         __u64 set_time_cc;
 297         int cc;
 298
 299         /* kick the TOD clock */
 300         asm volatile(
 301                 "       stck    0(%2)\n"
 302                 "       ipm     %0\n"
 303                 "       srl     %0,28"
 304                 : "=d" (cc), "=m" (init_timer_cc)
 305                 : "a" (&init_timer_cc) : "cc");
 306         switch (cc) {
 307         case 0: /* clock in set state: all is fine */
 308                 break;
 309         case 1: /* clock in non-set state: FIXME */
 310                 printk("time_init: TOD clock in non-set state\n");
 311                 break;
 312         case 2: /* clock in error state: FIXME */
 313                 printk("time_init: TOD clock in error state\n");
 314                 break;
 315         case 3: /* clock in stopped or not-operational state: FIXME */
 316                 printk("time_init: TOD clock stopped/non-operational\n");
 317                 break;
 318         }
 319         jiffies_timer_cc = init_timer_cc - jiffies_64 * CLK_TICKS_PER_JIFFY;
 320
 321         /* set xtime */
 322         xtime_cc = init_timer_cc + CLK_TICKS_PER_JIFFY;
 323         set_time_cc = init_timer_cc - 0x8126d60e46000000LL +
 324                 (0x3c26700LL*1000000*4096);
 325         tod_to_timeval(set_time_cc, &xtime);
 326         set_normalized_timespec(&wall_to_monotonic,
 327                                 -xtime.tv_sec, -xtime.tv_nsec);
 328
 329         /* request the clock comparator external interrupt */
 330         if (register_early_external_interrupt(0x1004, NULL,
 331                                               &ext_int_info_cc) != 0)
 332                 panic("Couldn't request external interrupt 0x1004");
 333
 334         if (clocksource_register(&clocksource_tod) != 0)
 335                 panic("Could not register TOD clock source");
 336
 337         init_cpu_timer();
 338
 339 #ifdef CONFIG_NO_IDLE_HZ
 340         nohz_init();
 341 #endif
 342
 343 #ifdef CONFIG_VIRT_TIMER
 344         vtime_init();
 345 #endif
 346 }
 347