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 void __init bcm2835_timer_init(struct device_node *node)
 84{
 85	void __iomem *base;
 86	u32 freq;
 87	int irq;
 88	struct bcm2835_timer *timer;
 89
 90	base = of_iomap(node, 0);
 91	if (!base)
 92		panic("Can't remap registers");
 93
 94	if (of_property_read_u32(node, "clock-frequency", &freq))
 95		panic("Can't read clock-frequency");
 96
 97	system_clock = base + REG_COUNTER_LO;
 98	sched_clock_register(bcm2835_sched_read, 32, freq);
 99
100	clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
101		freq, 300, 32, clocksource_mmio_readl_up);
102
103	irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
104	if (irq <= 0)
105		panic("Can't parse IRQ");
106
107	timer = kzalloc(sizeof(*timer), GFP_KERNEL);
108	if (!timer)
109		panic("Can't allocate timer struct\n");
110
111	timer->control = base + REG_CONTROL;
112	timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
113	timer->match_mask = BIT(DEFAULT_TIMER);
114	timer->evt.name = node->name;
115	timer->evt.rating = 300;
116	timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
117	timer->evt.set_next_event = bcm2835_time_set_next_event;
118	timer->evt.cpumask = cpumask_of(0);
119	timer->act.name = node->name;
120	timer->act.flags = IRQF_TIMER | IRQF_SHARED;
121	timer->act.dev_id = timer;
122	timer->act.handler = bcm2835_time_interrupt;
123
124	if (setup_irq(irq, &timer->act))
125		panic("Can't set up timer IRQ\n");
126
127	clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
128
129	pr_info("bcm2835: system timer (irq = %d)\n", irq);
130}
131CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
132			bcm2835_timer_init);