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/bitops.h>
  20#include <linux/clockchips.h>
  21#include <linux/clocksource.h>
  22#include <linux/interrupt.h>
  23#include <linux/irqreturn.h>
  24#include <linux/kernel.h>
  25#include <linux/module.h>
  26#include <linux/of_address.h>
  27#include <linux/of_irq.h>
  28#include <linux/of_platform.h>
  29#include <linux/slab.h>
  30#include <linux/string.h>
  31
  32#include <asm/sched_clock.h>
  33#include <asm/irq.h>
  34
  35#define REG_CONTROL     0x00
  36#define REG_COUNTER_LO  0x04
  37#define REG_COUNTER_HI  0x08
  38#define REG_COMPARE(n)  (0x0c + (n) * 4)
  39#define MAX_TIMER       3
  40#define DEFAULT_TIMER   3
  41
  42struct bcm2835_timer {
  43        void __iomem *control;
  44        void __iomem *compare;
  45        int match_mask;
  46        struct clock_event_device evt;
  47        struct irqaction act;
  48};
  49
  50static void __iomem *system_clock __read_mostly;
  51
  52static u32 notrace bcm2835_sched_read(void)
  53{
  54        return readl_relaxed(system_clock);
  55}
  56
  57static void bcm2835_time_set_mode(enum clock_event_mode mode,
  58        struct clock_event_device *evt_dev)
  59{
  60        switch (mode) {
  61        case CLOCK_EVT_MODE_ONESHOT:
  62        case CLOCK_EVT_MODE_UNUSED:
  63        case CLOCK_EVT_MODE_SHUTDOWN:
  64        case CLOCK_EVT_MODE_RESUME:
  65                break;
  66        default:
  67                WARN(1, "%s: unhandled event mode %d\n", __func__, mode);
  68                break;
  69        }
  70}
  71
  72static int bcm2835_time_set_next_event(unsigned long event,
  73        struct clock_event_device *evt_dev)
  74{
  75        struct bcm2835_timer *timer = container_of(evt_dev,
  76                struct bcm2835_timer, evt);
  77        writel_relaxed(readl_relaxed(system_clock) + event,
  78                timer->compare);
  79        return 0;
  80}
  81
  82static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
  83{
  84        struct bcm2835_timer *timer = dev_id;
  85        void (*event_handler)(struct clock_event_device *);
  86        if (readl_relaxed(timer->control) & timer->match_mask) {
  87                writel_relaxed(timer->match_mask, timer->control);
  88
  89                event_handler = ACCESS_ONCE(timer->evt.event_handler);
  90                if (event_handler)
  91                        event_handler(&timer->evt);
  92                return IRQ_HANDLED;
  93        } else {
  94                return IRQ_NONE;
  95        }
  96}
  97
  98static struct of_device_id bcm2835_time_match[] __initconst = {
  99        { .compatible = "brcm,bcm2835-system-timer" },
 100        {}
 101};
 102
 103static void __init bcm2835_timer_init(void)
 104{
 105        struct device_node *node;
 106        void __iomem *base;
 107        u32 freq;
 108        int irq;
 109        struct bcm2835_timer *timer;
 110
 111        node = of_find_matching_node(NULL, bcm2835_time_match);
 112        if (!node)
 113                panic("No bcm2835 timer node");
 114
 115        base = of_iomap(node, 0);
 116        if (!base)
 117                panic("Can't remap registers");
 118
 119        if (of_property_read_u32(node, "clock-frequency", &freq))
 120                panic("Can't read clock-frequency");
 121
 122        system_clock = base + REG_COUNTER_LO;
 123        setup_sched_clock(bcm2835_sched_read, 32, freq);
 124
 125        clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
 126                freq, 300, 32, clocksource_mmio_readl_up);
 127
 128        irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
 129        if (irq <= 0)
 130                panic("Can't parse IRQ");
 131
 132        timer = kzalloc(sizeof(*timer), GFP_KERNEL);
 133        if (!timer)
 134                panic("Can't allocate timer struct\n");
 135
 136        timer->control = base + REG_CONTROL;
 137        timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
 138        timer->match_mask = BIT(DEFAULT_TIMER);
 139        timer->evt.name = node->name;
 140        timer->evt.rating = 300;
 141        timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
 142        timer->evt.set_mode = bcm2835_time_set_mode;
 143        timer->evt.set_next_event = bcm2835_time_set_next_event;
 144        timer->evt.cpumask = cpumask_of(0);
 145        timer->act.name = node->name;
 146        timer->act.flags = IRQF_TIMER | IRQF_SHARED;
 147        timer->act.dev_id = timer;
 148        timer->act.handler = bcm2835_time_interrupt;
 149
 150        if (setup_irq(irq, &timer->act))
 151                panic("Can't set up timer IRQ\n");
 152
 153        clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
 154
 155        pr_info("bcm2835: system timer (irq = %d)\n", irq);
 156}
 157CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
 158                        bcm2835_timer_init);
 159
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