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 
42 struct 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 
50 static void __iomem *system_clock __read_mostly;
51 
52 static u64 notrace bcm2835_sched_read(void)
53 {
54 	return readl_relaxed(system_clock);
55 }
56 
57 static 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 
72 static 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 
82 static 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 
98 static 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 }
147 CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
148 			bcm2835_timer_init);
149