arch/tile/kernel/time.c

   1 /*
   2  * Copyright 2010 Tilera Corporation. All Rights Reserved.
   3  *
   4  *   This program is free software; you can redistribute it and/or
   5  *   modify it under the terms of the GNU General Public License
   6  *   as published by the Free Software Foundation, version 2.
   7  *
   8  *   This program is distributed in the hope that it will be useful, but
   9  *   WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  11  *   NON INFRINGEMENT.  See the GNU General Public License for
  12  *   more details.
  13  *
  14  * Support the cycle counter clocksource and tile timer clock event device.
  15  */
  16
  17 #include <linux/time.h>
  18 #include <linux/timex.h>
  19 #include <linux/clocksource.h>
  20 #include <linux/clockchips.h>
  21 #include <linux/hardirq.h>
  22 #include <linux/sched.h>
  23 #include <linux/smp.h>
  24 #include <linux/delay.h>
  25 #include <linux/module.h>
  26 #include <asm/irq_regs.h>
  27 #include <asm/traps.h>
  28 #include <hv/hypervisor.h>
  29 #include <arch/interrupts.h>
  30 #include <arch/spr_def.h>
  31
  32
  33 /*
  34  * Define the cycle counter clock source.
  35  */
  36
  37 /* How many cycles per second we are running at. */
  38 static cycles_t cycles_per_sec __write_once;
  39
  40 cycles_t get_clock_rate(void)
  41 {
  42         return cycles_per_sec;
  43 }
  44
  45 #if CHIP_HAS_SPLIT_CYCLE()
  46 cycles_t get_cycles(void)
  47 {
  48         unsigned int high = __insn_mfspr(SPR_CYCLE_HIGH);
  49         unsigned int low = __insn_mfspr(SPR_CYCLE_LOW);
  50         unsigned int high2 = __insn_mfspr(SPR_CYCLE_HIGH);
  51
  52         while (unlikely(high != high2)) {
  53                 low = __insn_mfspr(SPR_CYCLE_LOW);
  54                 high = high2;
  55                 high2 = __insn_mfspr(SPR_CYCLE_HIGH);
  56         }
  57
  58         return (((cycles_t)high) << 32) | low;
  59 }
  60 EXPORT_SYMBOL(get_cycles);
  61 #endif
  62
  63 /*
  64  * We use a relatively small shift value so that sched_clock()
  65  * won't wrap around very often.
  66  */
  67 #define SCHED_CLOCK_SHIFT 10
  68
  69 static unsigned long sched_clock_mult __write_once;
  70
  71 static cycles_t clocksource_get_cycles(struct clocksource *cs)
  72 {
  73         return get_cycles();
  74 }
  75
  76 static struct clocksource cycle_counter_cs = {
  77         .name = "cycle counter",
  78         .rating = 300,
  79         .read = clocksource_get_cycles,
  80         .mask = CLOCKSOURCE_MASK(64),
  81         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
  82 };
  83
  84 /*
  85  * Called very early from setup_arch() to set cycles_per_sec.
  86  * We initialize it early so we can use it to set up loops_per_jiffy.
  87  */
  88 void __init setup_clock(void)
  89 {
  90         cycles_per_sec = hv_sysconf(HV_SYSCONF_CPU_SPEED);
  91         sched_clock_mult =
  92                 clocksource_hz2mult(cycles_per_sec, SCHED_CLOCK_SHIFT);
  93 }
  94
  95 void __init calibrate_delay(void)
  96 {
  97         loops_per_jiffy = get_clock_rate() / HZ;
  98         pr_info("Clock rate yields %lu.%02lu BogoMIPS (lpj=%lu)\n",
  99                 loops_per_jiffy/(500000/HZ),
 100                 (loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy);
 101 }
 102
 103 /* Called fairly late in init/main.c, but before we go smp. */
 104 void __init time_init(void)
 105 {
 106         /* Initialize and register the clock source. */
 107         clocksource_register_hz(&cycle_counter_cs, cycles_per_sec);
 108
 109         /* Start up the tile-timer interrupt source on the boot cpu. */
 110         setup_tile_timer();
 111 }
 112
 113
 114 /*
 115  * Define the tile timer clock event device.  The timer is driven by
 116  * the TILE_TIMER_CONTROL register, which consists of a 31-bit down
 117  * counter, plus bit 31, which signifies that the counter has wrapped
 118  * from zero to (2**31) - 1.  The INT_TILE_TIMER interrupt will be
 119  * raised as long as bit 31 is set.
 120  *
 121  * The TILE_MINSEC value represents the largest range of real-time
 122  * we can possibly cover with the timer, based on MAX_TICK combined
 123  * with the slowest reasonable clock rate we might run at.
 124  */
 125
 126 #define MAX_TICK 0x7fffffff   /* we have 31 bits of countdown timer */
 127 #define TILE_MINSEC 5         /* timer covers no more than 5 seconds */
 128
 129 static int tile_timer_set_next_event(unsigned long ticks,
 130                                      struct clock_event_device *evt)
 131 {
 132         BUG_ON(ticks > MAX_TICK);
 133         __insn_mtspr(SPR_TILE_TIMER_CONTROL, ticks);
 134         arch_local_irq_unmask_now(INT_TILE_TIMER);
 135         return 0;
 136 }
 137
 138 /*
 139  * Whenever anyone tries to change modes, we just mask interrupts
 140  * and wait for the next event to get set.
 141  */
 142 static void tile_timer_set_mode(enum clock_event_mode mode,
 143                                 struct clock_event_device *evt)
 144 {
 145         arch_local_irq_mask_now(INT_TILE_TIMER);
 146 }
 147
 148 /*
 149  * Set min_delta_ns to 1 microsecond, since it takes about
 150  * that long to fire the interrupt.
 151  */
 152 static DEFINE_PER_CPU(struct clock_event_device, tile_timer) = {
 153         .name = "tile timer",
 154         .features = CLOCK_EVT_FEAT_ONESHOT,
 155         .min_delta_ns = 1000,
 156         .rating = 100,
 157         .irq = -1,
 158         .set_next_event = tile_timer_set_next_event,
 159         .set_mode = tile_timer_set_mode,
 160 };
 161
 162 void __cpuinit setup_tile_timer(void)
 163 {
 164         struct clock_event_device *evt = &__get_cpu_var(tile_timer);
 165
 166         /* Fill in fields that are speed-specific. */
 167         clockevents_calc_mult_shift(evt, cycles_per_sec, TILE_MINSEC);
 168         evt->max_delta_ns = clockevent_delta2ns(MAX_TICK, evt);
 169
 170         /* Mark as being for this cpu only. */
 171         evt->cpumask = cpumask_of(smp_processor_id());
 172
 173         /* Start out with timer not firing. */
 174         arch_local_irq_mask_now(INT_TILE_TIMER);
 175
 176         /* Register tile timer. */
 177         clockevents_register_device(evt);
 178 }
 179
 180 /* Called from the interrupt vector. */
 181 void do_timer_interrupt(struct pt_regs *regs, int fault_num)
 182 {
 183         struct pt_regs *old_regs = set_irq_regs(regs);
 184         struct clock_event_device *evt = &__get_cpu_var(tile_timer);
 185
 186         /*
 187          * Mask the timer interrupt here, since we are a oneshot timer
 188          * and there are now by definition no events pending.
 189          */
 190         arch_local_irq_mask(INT_TILE_TIMER);
 191
 192         /* Track time spent here in an interrupt context */
 193         irq_enter();
 194
 195         /* Track interrupt count. */
 196         __get_cpu_var(irq_stat).irq_timer_count++;
 197
 198         /* Call the generic timer handler */
 199         evt->event_handler(evt);
 200
 201         /*
 202          * Track time spent against the current process again and
 203          * process any softirqs if they are waiting.
 204          */
 205         irq_exit();
 206
 207         set_irq_regs(old_regs);
 208 }
 209
 210 /*
 211  * Scheduler clock - returns current time in nanosec units.
 212  * Note that with LOCKDEP, this is called during lockdep_init(), and
 213  * we will claim that sched_clock() is zero for a little while, until
 214  * we run setup_clock(), above.
 215  */
 216 unsigned long long sched_clock(void)
 217 {
 218         return clocksource_cyc2ns(get_cycles(),
 219                                   sched_clock_mult, SCHED_CLOCK_SHIFT);
 220 }
 221
 222 int setup_profiling_timer(unsigned int multiplier)
 223 {
 224         return -EINVAL;
 225 }
 226
 227 /*
 228  * Use the tile timer to convert nsecs to core clock cycles, relying
 229  * on it having the same frequency as SPR_CYCLE.
 230  */
 231 cycles_t ns2cycles(unsigned long nsecs)
 232 {
 233         struct clock_event_device *dev = &__get_cpu_var(tile_timer);
 234         return ((u64)nsecs * dev->mult) >> dev->shift;
 235 }