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
bcm2835_sched_read(void)38 static u64 notrace bcm2835_sched_read(void)
39 {
40 return readl_relaxed(system_clock);
41 }
42
bcm2835_time_set_next_event(unsigned long event,struct clock_event_device * evt_dev)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
bcm2835_time_interrupt(int irq,void * dev_id)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
bcm2835_timer_init(struct device_node * node)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