LXR linux/drivers/clocksource/bcm2835

   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#include <linux/sched_clock.h>
  32
  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 u64 notrace bcm2835_sched_read(void)
  53{
  54        return readl_relaxed(system_clock);
  55}
  56
  57static int bcm2835_time_set_next_event(unsigned long event,
  58        struct clock_event_device *evt_dev)
  59{
  60        struct bcm2835_timer *timer = container_of(evt_dev,
  61                struct bcm2835_timer, evt);
  62        writel_relaxed(readl_relaxed(system_clock) + event,
  63                timer->compare);
  64        return 0;
  65}
  66
  67static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
  68{
  69        struct bcm2835_timer *timer = dev_id;
  70        void (*event_handler)(struct clock_event_device *);
  71        if (readl_relaxed(timer->control) & timer->match_mask) {
  72                writel_relaxed(timer->match_mask, timer->control);
  73
  74                event_handler = ACCESS_ONCE(timer->evt.event_handler);
  75                if (event_handler)
  76                        event_handler(&timer->evt);
  77                return IRQ_HANDLED;
  78        } else {
  79                return IRQ_NONE;
  80        }
  81}
  82
  83static int __init bcm2835_timer_init(struct device_node *node)
  84{
  85        void __iomem *base;
  86        u32 freq;
  87        int irq, ret;
  88        struct bcm2835_timer *timer;
  89
  90        base = of_iomap(node, 0);
  91        if (!base) {
  92                pr_err("Can't remap registers");
  93                return -ENXIO;
  94        }
  95
  96        ret = of_property_read_u32(node, "clock-frequency", &freq);
  97        if (ret) {
  98                pr_err("Can't read clock-frequency");
  99                return ret;
 100        }
 101
 102        system_clock = base + REG_COUNTER_LO;
 103        sched_clock_register(bcm2835_sched_read, 32, freq);
 104
 105        clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
 106                freq, 300, 32, clocksource_mmio_readl_up);
 107
 108        irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
 109        if (irq <= 0) {
 110                pr_err("Can't parse IRQ");
 111                return -EINVAL;
 112        }
 113
 114        timer = kzalloc(sizeof(*timer), GFP_KERNEL);
 115        if (!timer) {
 116                pr_err("Can't allocate timer struct\n");
 117                return -ENOMEM;
 118        }
 119
 120        timer->control = base + REG_CONTROL;
 121        timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
 122        timer->match_mask = BIT(DEFAULT_TIMER);
 123        timer->evt.name = node->name;
 124        timer->evt.rating = 300;
 125        timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
 126        timer->evt.set_next_event = bcm2835_time_set_next_event;
 127        timer->evt.cpumask = cpumask_of(0);
 128        timer->act.name = node->name;
 129        timer->act.flags = IRQF_TIMER | IRQF_SHARED;
 130        timer->act.dev_id = timer;
 131        timer->act.handler = bcm2835_time_interrupt;
 132
 133        ret = setup_irq(irq, &timer->act);
 134        if (ret) {
 135                pr_err("Can't set up timer IRQ\n");
 136                return ret;
 137        }
 138
 139        clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
 140
 141        pr_info("bcm2835: system timer (irq = %d)\n", irq);
 142
 143        return 0;
 144}
 145CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
 146                        bcm2835_timer_init);
 147