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		goto err_iounmap;
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		ret = -EINVAL;
112		goto err_iounmap;
113	}
114
115	timer = kzalloc(sizeof(*timer), GFP_KERNEL);
116	if (!timer) {
117		pr_err("Can't allocate timer struct\n");
118		ret = -ENOMEM;
119		goto err_iounmap;
120	}
121
122	timer->control = base + REG_CONTROL;
123	timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
124	timer->match_mask = BIT(DEFAULT_TIMER);
125	timer->evt.name = node->name;
126	timer->evt.rating = 300;
127	timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
128	timer->evt.set_next_event = bcm2835_time_set_next_event;
129	timer->evt.cpumask = cpumask_of(0);
130	timer->act.name = node->name;
131	timer->act.flags = IRQF_TIMER | IRQF_SHARED;
132	timer->act.dev_id = timer;
133	timer->act.handler = bcm2835_time_interrupt;
134
135	ret = setup_irq(irq, &timer->act);
136	if (ret) {
137		pr_err("Can't set up timer IRQ\n");
138		goto err_iounmap;
139	}
140
141	clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
142
143	pr_info("bcm2835: system timer (irq = %d)\n", irq);
144
145	return 0;
146
147err_iounmap:
148	iounmap(base);
149	return ret;
150}
151CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
152			bcm2835_timer_init);