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 
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 
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 
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 
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 
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