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/cpu.h>
  10 #include <linux/init.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/irqchip/mips-gic.h>
  13 #include <linux/notifier.h>
  14 #include <linux/percpu.h>
  15 #include <linux/smp.h>
  16 #include <linux/time.h>
  17
  18 static DEFINE_PER_CPU(struct clock_event_device, gic_clockevent_device);
  19 static int gic_timer_irq;
  20 static unsigned int gic_frequency;
  21
  22 static int gic_next_event(unsigned long delta, struct clock_event_device *evt)
  23 {
  24         u64 cnt;
  25         int res;
  26
  27         cnt = gic_read_count();
  28         cnt += (u64)delta;
  29         gic_write_cpu_compare(cnt, cpumask_first(evt->cpumask));
  30         res = ((int)(gic_read_count() - cnt) >= 0) ? -ETIME : 0;
  31         return res;
  32 }
  33
  34 static void gic_set_clock_mode(enum clock_event_mode mode,
  35                                 struct clock_event_device *evt)
  36 {
  37         /* Nothing to do ...  */
  38 }
  39
  40 static irqreturn_t gic_compare_interrupt(int irq, void *dev_id)
  41 {
  42         struct clock_event_device *cd = dev_id;
  43
  44         gic_write_compare(gic_read_compare());
  45         cd->event_handler(cd);
  46         return IRQ_HANDLED;
  47 }
  48
  49 struct irqaction gic_compare_irqaction = {
  50         .handler = gic_compare_interrupt,
  51         .percpu_dev_id = &gic_clockevent_device,
  52         .flags = IRQF_PERCPU | IRQF_TIMER,
  53         .name = "timer",
  54 };
  55
  56 static void gic_clockevent_cpu_init(struct clock_event_device *cd)
  57 {
  58         unsigned int cpu = smp_processor_id();
  59
  60         cd->name                = "MIPS GIC";
  61         cd->features            = CLOCK_EVT_FEAT_ONESHOT |
  62                                   CLOCK_EVT_FEAT_C3STOP;
  63
  64         cd->rating              = 300;
  65         cd->irq                 = gic_timer_irq;
  66         cd->cpumask             = cpumask_of(cpu);
  67         cd->set_next_event      = gic_next_event;
  68         cd->set_mode            = gic_set_clock_mode;
  69
  70         clockevents_config_and_register(cd, gic_frequency, 0x300, 0x7fffffff);
  71
  72         enable_percpu_irq(gic_timer_irq, IRQ_TYPE_NONE);
  73 }
  74
  75 static void gic_clockevent_cpu_exit(struct clock_event_device *cd)
  76 {
  77         disable_percpu_irq(gic_timer_irq);
  78 }
  79
  80 static int gic_cpu_notifier(struct notifier_block *nb, unsigned long action,
  81                                 void *data)
  82 {
  83         switch (action & ~CPU_TASKS_FROZEN) {
  84         case CPU_STARTING:
  85                 gic_clockevent_cpu_init(this_cpu_ptr(&gic_clockevent_device));
  86                 break;
  87         case CPU_DYING:
  88                 gic_clockevent_cpu_exit(this_cpu_ptr(&gic_clockevent_device));
  89                 break;
  90         }
  91
  92         return NOTIFY_OK;
  93 }
  94
  95 static struct notifier_block gic_cpu_nb = {
  96         .notifier_call = gic_cpu_notifier,
  97 };
  98
  99 static int gic_clockevent_init(void)
 100 {
 101         if (!cpu_has_counter || !gic_frequency)
 102                 return -ENXIO;
 103
 104         gic_timer_irq = MIPS_GIC_IRQ_BASE +
 105                 GIC_LOCAL_TO_HWIRQ(GIC_LOCAL_INT_COMPARE);
 106         setup_percpu_irq(gic_timer_irq, &gic_compare_irqaction);
 107
 108         register_cpu_notifier(&gic_cpu_nb);
 109
 110         gic_clockevent_cpu_init(this_cpu_ptr(&gic_clockevent_device));
 111
 112         return 0;
 113 }
 114
 115 static cycle_t gic_hpt_read(struct clocksource *cs)
 116 {
 117         return gic_read_count();
 118 }
 119
 120 static struct clocksource gic_clocksource = {
 121         .name   = "GIC",
 122         .read   = gic_hpt_read,
 123         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 124 };
 125
 126 void __init gic_clocksource_init(unsigned int frequency)
 127 {
 128         gic_frequency = frequency;
 129
 130         /* Set clocksource mask. */
 131         gic_clocksource.mask = CLOCKSOURCE_MASK(gic_get_count_width());
 132
 133         /* Calculate a somewhat reasonable rating value. */
 134         gic_clocksource.rating = 200 + frequency / 10000000;
 135
 136         clocksource_register_hz(&gic_clocksource, frequency);
 137
 138         gic_clockevent_init();
 139 }