1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Copyright 2012 Simon Arlott
4  */
5 
6 #include <linux/bitops.h>
7 #include <linux/clockchips.h>
8 #include <linux/clocksource.h>
9 #include <linux/interrupt.h>
10 #include <linux/irqreturn.h>
11 #include <linux/kernel.h>
12 #include <linux/module.h>
13 #include <linux/of.h>
14 #include <linux/of_address.h>
15 #include <linux/of_irq.h>
16 #include <linux/slab.h>
17 #include <linux/string.h>
18 #include <linux/sched_clock.h>
19 
20 #include <asm/irq.h>
21 
22 #define REG_CONTROL	0x00
23 #define REG_COUNTER_LO	0x04
24 #define REG_COUNTER_HI	0x08
25 #define REG_COMPARE(n)	(0x0c + (n) * 4)
26 #define MAX_TIMER	3
27 #define DEFAULT_TIMER	3
28 
29 struct bcm2835_timer {
30 	void __iomem *control;
31 	void __iomem *compare;
32 	int match_mask;
33 	struct clock_event_device evt;
34 };
35 
36 static void __iomem *system_clock __read_mostly;
37 
38 static u64 notrace bcm2835_sched_read(void)
39 {
40 	return readl_relaxed(system_clock);
41 }
42 
43 static int bcm2835_time_set_next_event(unsigned long event,
44 	struct clock_event_device *evt_dev)
45 {
46 	struct bcm2835_timer *timer = container_of(evt_dev,
47 		struct bcm2835_timer, evt);
48 	writel_relaxed(readl_relaxed(system_clock) + event,
49 		timer->compare);
50 	return 0;
51 }
52 
53 static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
54 {
55 	struct bcm2835_timer *timer = dev_id;
56 	void (*event_handler)(struct clock_event_device *);
57 	if (readl_relaxed(timer->control) & timer->match_mask) {
58 		writel_relaxed(timer->match_mask, timer->control);
59 
60 		event_handler = READ_ONCE(timer->evt.event_handler);
61 		if (event_handler)
62 			event_handler(&timer->evt);
63 		return IRQ_HANDLED;
64 	} else {
65 		return IRQ_NONE;
66 	}
67 }
68 
69 static int __init bcm2835_timer_init(struct device_node *node)
70 {
71 	void __iomem *base;
72 	u32 freq;
73 	int irq, ret;
74 	struct bcm2835_timer *timer;
75 
76 	base = of_iomap(node, 0);
77 	if (!base) {
78 		pr_err("Can't remap registers\n");
79 		return -ENXIO;
80 	}
81 
82 	ret = of_property_read_u32(node, "clock-frequency", &freq);
83 	if (ret) {
84 		pr_err("Can't read clock-frequency\n");
85 		goto err_iounmap;
86 	}
87 
88 	system_clock = base + REG_COUNTER_LO;
89 	sched_clock_register(bcm2835_sched_read, 32, freq);
90 
91 	clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
92 		freq, 300, 32, clocksource_mmio_readl_up);
93 
94 	irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
95 	if (irq <= 0) {
96 		pr_err("Can't parse IRQ\n");
97 		ret = -EINVAL;
98 		goto err_iounmap;
99 	}
100 
101 	timer = kzalloc(sizeof(*timer), GFP_KERNEL);
102 	if (!timer) {
103 		ret = -ENOMEM;
104 		goto err_iounmap;
105 	}
106 
107 	timer->control = base + REG_CONTROL;
108 	timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
109 	timer->match_mask = BIT(DEFAULT_TIMER);
110 	timer->evt.name = node->name;
111 	timer->evt.rating = 300;
112 	timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
113 	timer->evt.set_next_event = bcm2835_time_set_next_event;
114 	timer->evt.cpumask = cpumask_of(0);
115 
116 	ret = request_irq(irq, bcm2835_time_interrupt, IRQF_TIMER | IRQF_SHARED,
117 			  node->name, timer);
118 	if (ret) {
119 		pr_err("Can't set up timer IRQ\n");
120 		goto err_timer_free;
121 	}
122 
123 	clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
124 
125 	pr_info("bcm2835: system timer (irq = %d)\n", irq);
126 
127 	return 0;
128 
129 err_timer_free:
130 	kfree(timer);
131 
132 err_iounmap:
133 	iounmap(base);
134 	return ret;
135 }
136 TIMER_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
137 			bcm2835_timer_init);
138