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_address.h>
14 #include <linux/of_irq.h>
15 #include <linux/of_platform.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 struct irqaction act;
35 };
36
37 static void __iomem *system_clock __read_mostly;
38
bcm2835_sched_read(void)39 static u64 notrace bcm2835_sched_read(void)
40 {
41 return readl_relaxed(system_clock);
42 }
43
bcm2835_time_set_next_event(unsigned long event,struct clock_event_device * evt_dev)44 static int bcm2835_time_set_next_event(unsigned long event,
45 struct clock_event_device *evt_dev)
46 {
47 struct bcm2835_timer *timer = container_of(evt_dev,
48 struct bcm2835_timer, evt);
49 writel_relaxed(readl_relaxed(system_clock) + event,
50 timer->compare);
51 return 0;
52 }
53
bcm2835_time_interrupt(int irq,void * dev_id)54 static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
55 {
56 struct bcm2835_timer *timer = dev_id;
57 void (*event_handler)(struct clock_event_device *);
58 if (readl_relaxed(timer->control) & timer->match_mask) {
59 writel_relaxed(timer->match_mask, timer->control);
60
61 event_handler = READ_ONCE(timer->evt.event_handler);
62 if (event_handler)
63 event_handler(&timer->evt);
64 return IRQ_HANDLED;
65 } else {
66 return IRQ_NONE;
67 }
68 }
69
bcm2835_timer_init(struct device_node * node)70 static int __init bcm2835_timer_init(struct device_node *node)
71 {
72 void __iomem *base;
73 u32 freq;
74 int irq, ret;
75 struct bcm2835_timer *timer;
76
77 base = of_iomap(node, 0);
78 if (!base) {
79 pr_err("Can't remap registers\n");
80 return -ENXIO;
81 }
82
83 ret = of_property_read_u32(node, "clock-frequency", &freq);
84 if (ret) {
85 pr_err("Can't read clock-frequency\n");
86 goto err_iounmap;
87 }
88
89 system_clock = base + REG_COUNTER_LO;
90 sched_clock_register(bcm2835_sched_read, 32, freq);
91
92 clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
93 freq, 300, 32, clocksource_mmio_readl_up);
94
95 irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
96 if (irq <= 0) {
97 pr_err("Can't parse IRQ\n");
98 ret = -EINVAL;
99 goto err_iounmap;
100 }
101
102 timer = kzalloc(sizeof(*timer), GFP_KERNEL);
103 if (!timer) {
104 ret = -ENOMEM;
105 goto err_iounmap;
106 }
107
108 timer->control = base + REG_CONTROL;
109 timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
110 timer->match_mask = BIT(DEFAULT_TIMER);
111 timer->evt.name = node->name;
112 timer->evt.rating = 300;
113 timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
114 timer->evt.set_next_event = bcm2835_time_set_next_event;
115 timer->evt.cpumask = cpumask_of(0);
116 timer->act.name = node->name;
117 timer->act.flags = IRQF_TIMER | IRQF_SHARED;
118 timer->act.dev_id = timer;
119 timer->act.handler = bcm2835_time_interrupt;
120
121 ret = setup_irq(irq, &timer->act);
122 if (ret) {
123 pr_err("Can't set up timer IRQ\n");
124 goto err_iounmap;
125 }
126
127 clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
128
129 pr_info("bcm2835: system timer (irq = %d)\n", irq);
130
131 return 0;
132
133 err_iounmap:
134 iounmap(base);
135 return ret;
136 }
137 TIMER_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
138 bcm2835_timer_init);
139