linux/drivers/clocksource/bcm2835_timer.c
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   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
  43struct 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
  51static void __iomem *system_clock __read_mostly;
  52
  53static u32 notrace bcm2835_sched_read(void)
  54{
  55        return readl_relaxed(system_clock);
  56}
  57
  58static 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
  73static 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
  83static 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
  99static struct of_device_id bcm2835_time_match[] __initconst = {
 100        { .compatible = "brcm,bcm2835-system-timer" },
 101        {}
 102};
 103
 104static void __init bcm2835_time_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}
 158
 159struct sys_timer bcm2835_timer = {
 160        .init = bcm2835_time_init,
 161};
 162
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