drivers/clocksource/bcm2835_timer.c

   1 /*
   2  * Copyright 2012 Simon Arlott
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17  */
  18
  19 #include <linux/bcm2835_timer.h>
  20 #include <linux/bitops.h>
  21 #include <linux/clockchips.h>
  22 #include <linux/clocksource.h>
  23 #include <linux/interrupt.h>
  24 #include <linux/irqreturn.h>
  25 #include <linux/kernel.h>
  26 #include <linux/module.h>
  27 #include <linux/of_address.h>
  28 #include <linux/of_irq.h>
  29 #include <linux/of_platform.h>
  30 #include <linux/slab.h>
  31 #include <linux/string.h>
  32
  33 #include <asm/sched_clock.h>
  34 #include <asm/irq.h>
  35
  36 #define REG_CONTROL     0x00
  37 #define REG_COUNTER_LO  0x04
  38 #define REG_COUNTER_HI  0x08
  39 #define REG_COMPARE(n)  (0x0c + (n) * 4)
  40 #define MAX_TIMER       3
  41 #define DEFAULT_TIMER   3
  42
  43 struct bcm2835_timer {
  44         void __iomem *control;
  45         void __iomem *compare;
  46         int match_mask;
  47         struct clock_event_device evt;
  48         struct irqaction act;
  49 };
  50
  51 static void __iomem *system_clock __read_mostly;
  52
  53 static u32 notrace bcm2835_sched_read(void)
  54 {
  55         return readl_relaxed(system_clock);
  56 }
  57
  58 static void bcm2835_time_set_mode(enum clock_event_mode mode,
  59         struct clock_event_device *evt_dev)
  60 {
  61         switch (mode) {
  62         case CLOCK_EVT_MODE_ONESHOT:
  63         case CLOCK_EVT_MODE_UNUSED:
  64         case CLOCK_EVT_MODE_SHUTDOWN:
  65         case CLOCK_EVT_MODE_RESUME:
  66                 break;
  67         default:
  68                 WARN(1, "%s: unhandled event mode %d\n", __func__, mode);
  69                 break;
  70         }
  71 }
  72
  73 static int bcm2835_time_set_next_event(unsigned long event,
  74         struct clock_event_device *evt_dev)
  75 {
  76         struct bcm2835_timer *timer = container_of(evt_dev,
  77                 struct bcm2835_timer, evt);
  78         writel_relaxed(readl_relaxed(system_clock) + event,
  79                 timer->compare);
  80         return 0;
  81 }
  82
  83 static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
  84 {
  85         struct bcm2835_timer *timer = dev_id;
  86         void (*event_handler)(struct clock_event_device *);
  87         if (readl_relaxed(timer->control) & timer->match_mask) {
  88                 writel_relaxed(timer->match_mask, timer->control);
  89
  90                 event_handler = ACCESS_ONCE(timer->evt.event_handler);
  91                 if (event_handler)
  92                         event_handler(&timer->evt);
  93                 return IRQ_HANDLED;
  94         } else {
  95                 return IRQ_NONE;
  96         }
  97 }
  98
  99 static struct of_device_id bcm2835_time_match[] __initconst = {
 100         { .compatible = "brcm,bcm2835-system-timer" },
 101         {}
 102 };
 103
 104 void __init bcm2835_timer_init(void)
 105 {
 106         struct device_node *node;
 107         void __iomem *base;
 108         u32 freq;
 109         int irq;
 110         struct bcm2835_timer *timer;
 111
 112         node = of_find_matching_node(NULL, bcm2835_time_match);
 113         if (!node)
 114                 panic("No bcm2835 timer node");
 115
 116         base = of_iomap(node, 0);
 117         if (!base)
 118                 panic("Can't remap registers");
 119
 120         if (of_property_read_u32(node, "clock-frequency", &freq))
 121                 panic("Can't read clock-frequency");
 122
 123         system_clock = base + REG_COUNTER_LO;
 124         setup_sched_clock(bcm2835_sched_read, 32, freq);
 125
 126         clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
 127                 freq, 300, 32, clocksource_mmio_readl_up);
 128
 129         irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
 130         if (irq <= 0)
 131                 panic("Can't parse IRQ");
 132
 133         timer = kzalloc(sizeof(*timer), GFP_KERNEL);
 134         if (!timer)
 135                 panic("Can't allocate timer struct\n");
 136
 137         timer->control = base + REG_CONTROL;
 138         timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
 139         timer->match_mask = BIT(DEFAULT_TIMER);
 140         timer->evt.name = node->name;
 141         timer->evt.rating = 300;
 142         timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
 143         timer->evt.set_mode = bcm2835_time_set_mode;
 144         timer->evt.set_next_event = bcm2835_time_set_next_event;
 145         timer->evt.cpumask = cpumask_of(0);
 146         timer->act.name = node->name;
 147         timer->act.flags = IRQF_TIMER | IRQF_SHARED;
 148         timer->act.dev_id = timer;
 149         timer->act.handler = bcm2835_time_interrupt;
 150
 151         if (setup_irq(irq, &timer->act))
 152                 panic("Can't set up timer IRQ\n");
 153
 154         clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
 155
 156         pr_info("bcm2835: system timer (irq = %d)\n", irq);
 157 }