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 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 void __init bcm2835_timer_init(struct device_node *node)
99{
100	void __iomem *base;
101	u32 freq;
102	int irq;
103	struct bcm2835_timer *timer;
104
105	base = of_iomap(node, 0);
106	if (!base)
107		panic("Can't remap registers");
108
109	if (of_property_read_u32(node, "clock-frequency", &freq))
110		panic("Can't read clock-frequency");
111
112	system_clock = base + REG_COUNTER_LO;
113	sched_clock_register(bcm2835_sched_read, 32, freq);
114
115	clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
116		freq, 300, 32, clocksource_mmio_readl_up);
117
118	irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
119	if (irq <= 0)
120		panic("Can't parse IRQ");
121
122	timer = kzalloc(sizeof(*timer), GFP_KERNEL);
123	if (!timer)
124		panic("Can't allocate timer struct\n");
125
126	timer->control = base + REG_CONTROL;
127	timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
128	timer->match_mask = BIT(DEFAULT_TIMER);
129	timer->evt.name = node->name;
130	timer->evt.rating = 300;
131	timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
132	timer->evt.set_mode = bcm2835_time_set_mode;
133	timer->evt.set_next_event = bcm2835_time_set_next_event;
134	timer->evt.cpumask = cpumask_of(0);
135	timer->act.name = node->name;
136	timer->act.flags = IRQF_TIMER | IRQF_SHARED;
137	timer->act.dev_id = timer;
138	timer->act.handler = bcm2835_time_interrupt;
139
140	if (setup_irq(irq, &timer->act))
141		panic("Can't set up timer IRQ\n");
142
143	clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
144
145	pr_info("bcm2835: system timer (irq = %d)\n", irq);
146}
147CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
148			bcm2835_timer_init);
149