drivers/clocksource/mips-gic-timer.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 2012 MIPS Technologies, Inc.  All rights reserved.
   7  */
   8 #include <linux/clockchips.h>
   9 #include <linux/init.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/irqchip/mips-gic.h>
  12 #include <linux/percpu.h>
  13 #include <linux/smp.h>
  14 #include <linux/time.h>
  15
  16 #include <asm/time.h>
  17
  18 static DEFINE_PER_CPU(struct clock_event_device, gic_clockevent_device);
  19 static int gic_timer_irq_installed;
  20
  21 static int gic_next_event(unsigned long delta, struct clock_event_device *evt)
  22 {
  23         u64 cnt;
  24         int res;
  25
  26         cnt = gic_read_count();
  27         cnt += (u64)delta;
  28         gic_write_cpu_compare(cnt, cpumask_first(evt->cpumask));
  29         res = ((int)(gic_read_count() - cnt) >= 0) ? -ETIME : 0;
  30         return res;
  31 }
  32
  33 static void gic_set_clock_mode(enum clock_event_mode mode,
  34                                 struct clock_event_device *evt)
  35 {
  36         /* Nothing to do ...  */
  37 }
  38
  39 static irqreturn_t gic_compare_interrupt(int irq, void *dev_id)
  40 {
  41         struct clock_event_device *cd;
  42         int cpu = smp_processor_id();
  43
  44         gic_write_compare(gic_read_compare());
  45         cd = &per_cpu(gic_clockevent_device, cpu);
  46         cd->event_handler(cd);
  47         return IRQ_HANDLED;
  48 }
  49
  50 struct irqaction gic_compare_irqaction = {
  51         .handler = gic_compare_interrupt,
  52         .flags = IRQF_PERCPU | IRQF_TIMER,
  53         .name = "timer",
  54 };
  55
  56 static void gic_event_handler(struct clock_event_device *dev)
  57 {
  58 }
  59
  60 int gic_clockevent_init(void)
  61 {
  62         unsigned int cpu = smp_processor_id();
  63         struct clock_event_device *cd;
  64         unsigned int irq;
  65
  66         if (!cpu_has_counter || !gic_frequency)
  67                 return -ENXIO;
  68
  69         irq = MIPS_GIC_IRQ_BASE + GIC_LOCAL_TO_HWIRQ(GIC_LOCAL_INT_COMPARE);
  70
  71         cd = &per_cpu(gic_clockevent_device, cpu);
  72
  73         cd->name                = "MIPS GIC";
  74         cd->features            = CLOCK_EVT_FEAT_ONESHOT |
  75                                   CLOCK_EVT_FEAT_C3STOP;
  76
  77         clockevent_set_clock(cd, gic_frequency);
  78
  79         /* Calculate the min / max delta */
  80         cd->max_delta_ns        = clockevent_delta2ns(0x7fffffff, cd);
  81         cd->min_delta_ns        = clockevent_delta2ns(0x300, cd);
  82
  83         cd->rating              = 300;
  84         cd->irq                 = irq;
  85         cd->cpumask             = cpumask_of(cpu);
  86         cd->set_next_event      = gic_next_event;
  87         cd->set_mode            = gic_set_clock_mode;
  88         cd->event_handler       = gic_event_handler;
  89
  90         clockevents_register_device(cd);
  91
  92         if (!gic_timer_irq_installed) {
  93                 setup_percpu_irq(irq, &gic_compare_irqaction);
  94                 gic_timer_irq_installed = 1;
  95         }
  96
  97         enable_percpu_irq(irq, IRQ_TYPE_NONE);
  98
  99         return 0;
 100 }
 101
 102 static cycle_t gic_hpt_read(struct clocksource *cs)
 103 {
 104         return gic_read_count();
 105 }
 106
 107 static struct clocksource gic_clocksource = {
 108         .name   = "GIC",
 109         .read   = gic_hpt_read,
 110         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 111 };
 112
 113 void __init gic_clocksource_init(unsigned int frequency)
 114 {
 115         /* Set clocksource mask. */
 116         gic_clocksource.mask = CLOCKSOURCE_MASK(gic_get_count_width());
 117
 118         /* Calculate a somewhat reasonable rating value. */
 119         gic_clocksource.rating = 200 + frequency / 10000000;
 120
 121         clocksource_register_hz(&gic_clocksource, frequency);
 122 }