1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * arch/arm/mach-vt8500/timer.c
4 *
5 * Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz>
6 * Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
7 */
8
9 /*
10 * This file is copied and modified from the original timer.c provided by
11 * Alexey Charkov. Minor changes have been made for Device Tree Support.
12 */
13
14 #include <linux/io.h>
15 #include <linux/irq.h>
16 #include <linux/interrupt.h>
17 #include <linux/clocksource.h>
18 #include <linux/clockchips.h>
19 #include <linux/delay.h>
20
21 #include <linux/of.h>
22 #include <linux/of_address.h>
23 #include <linux/of_irq.h>
24
25 #define VT8500_TIMER_OFFSET 0x0100
26 #define VT8500_TIMER_HZ 3000000
27 #define TIMER_MATCH_VAL 0x0000
28 #define TIMER_COUNT_VAL 0x0010
29 #define TIMER_STATUS_VAL 0x0014
30 #define TIMER_IER_VAL 0x001c /* interrupt enable */
31 #define TIMER_CTRL_VAL 0x0020
32 #define TIMER_AS_VAL 0x0024 /* access status */
33 #define TIMER_COUNT_R_ACTIVE (1 << 5) /* not ready for read */
34 #define TIMER_COUNT_W_ACTIVE (1 << 4) /* not ready for write */
35 #define TIMER_MATCH_W_ACTIVE (1 << 0) /* not ready for write */
36
37 #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
38
39 #define MIN_OSCR_DELTA 16
40
41 static void __iomem *regbase;
42
vt8500_timer_read(struct clocksource * cs)43 static u64 vt8500_timer_read(struct clocksource *cs)
44 {
45 int loops = msecs_to_loops(10);
46 writel(3, regbase + TIMER_CTRL_VAL);
47 while ((readl((regbase + TIMER_AS_VAL)) & TIMER_COUNT_R_ACTIVE)
48 && --loops)
49 cpu_relax();
50 return readl(regbase + TIMER_COUNT_VAL);
51 }
52
53 static struct clocksource clocksource = {
54 .name = "vt8500_timer",
55 .rating = 200,
56 .read = vt8500_timer_read,
57 .mask = CLOCKSOURCE_MASK(32),
58 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
59 };
60
vt8500_timer_set_next_event(unsigned long cycles,struct clock_event_device * evt)61 static int vt8500_timer_set_next_event(unsigned long cycles,
62 struct clock_event_device *evt)
63 {
64 int loops = msecs_to_loops(10);
65 u64 alarm = clocksource.read(&clocksource) + cycles;
66 while ((readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE)
67 && --loops)
68 cpu_relax();
69 writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL);
70
71 if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA)
72 return -ETIME;
73
74 writel(1, regbase + TIMER_IER_VAL);
75
76 return 0;
77 }
78
vt8500_shutdown(struct clock_event_device * evt)79 static int vt8500_shutdown(struct clock_event_device *evt)
80 {
81 writel(readl(regbase + TIMER_CTRL_VAL) | 1, regbase + TIMER_CTRL_VAL);
82 writel(0, regbase + TIMER_IER_VAL);
83 return 0;
84 }
85
86 static struct clock_event_device clockevent = {
87 .name = "vt8500_timer",
88 .features = CLOCK_EVT_FEAT_ONESHOT,
89 .rating = 200,
90 .set_next_event = vt8500_timer_set_next_event,
91 .set_state_shutdown = vt8500_shutdown,
92 .set_state_oneshot = vt8500_shutdown,
93 };
94
vt8500_timer_interrupt(int irq,void * dev_id)95 static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
96 {
97 struct clock_event_device *evt = dev_id;
98 writel(0xf, regbase + TIMER_STATUS_VAL);
99 evt->event_handler(evt);
100
101 return IRQ_HANDLED;
102 }
103
vt8500_timer_init(struct device_node * np)104 static int __init vt8500_timer_init(struct device_node *np)
105 {
106 int timer_irq, ret;
107
108 regbase = of_iomap(np, 0);
109 if (!regbase) {
110 pr_err("%s: Missing iobase description in Device Tree\n",
111 __func__);
112 return -ENXIO;
113 }
114
115 timer_irq = irq_of_parse_and_map(np, 0);
116 if (!timer_irq) {
117 pr_err("%s: Missing irq description in Device Tree\n",
118 __func__);
119 return -EINVAL;
120 }
121
122 writel(1, regbase + TIMER_CTRL_VAL);
123 writel(0xf, regbase + TIMER_STATUS_VAL);
124 writel(~0, regbase + TIMER_MATCH_VAL);
125
126 ret = clocksource_register_hz(&clocksource, VT8500_TIMER_HZ);
127 if (ret) {
128 pr_err("%s: clocksource_register failed for %s\n",
129 __func__, clocksource.name);
130 return ret;
131 }
132
133 clockevent.cpumask = cpumask_of(0);
134
135 ret = request_irq(timer_irq, vt8500_timer_interrupt,
136 IRQF_TIMER | IRQF_IRQPOLL, "vt8500_timer",
137 &clockevent);
138 if (ret) {
139 pr_err("%s: setup_irq failed for %s\n", __func__,
140 clockevent.name);
141 return ret;
142 }
143
144 clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ,
145 MIN_OSCR_DELTA * 2, 0xf0000000);
146
147 return 0;
148 }
149
150 TIMER_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init);
151