1 /*
2 * arch/arm/mach-vt8500/timer.c
3 *
4 * Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz>
5 * Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 */
21
22 /*
23 * This file is copied and modified from the original timer.c provided by
24 * Alexey Charkov. Minor changes have been made for Device Tree Support.
25 */
26
27 #include <linux/io.h>
28 #include <linux/irq.h>
29 #include <linux/interrupt.h>
30 #include <linux/clocksource.h>
31 #include <linux/clockchips.h>
32 #include <linux/delay.h>
33 #include <asm/mach/time.h>
34
35 #include <linux/of.h>
36 #include <linux/of_address.h>
37 #include <linux/of_irq.h>
38
39 #define VT8500_TIMER_OFFSET 0x0100
40 #define VT8500_TIMER_HZ 3000000
41 #define TIMER_MATCH_VAL 0x0000
42 #define TIMER_COUNT_VAL 0x0010
43 #define TIMER_STATUS_VAL 0x0014
44 #define TIMER_IER_VAL 0x001c /* interrupt enable */
45 #define TIMER_CTRL_VAL 0x0020
46 #define TIMER_AS_VAL 0x0024 /* access status */
47 #define TIMER_COUNT_R_ACTIVE (1 << 5) /* not ready for read */
48 #define TIMER_COUNT_W_ACTIVE (1 << 4) /* not ready for write */
49 #define TIMER_MATCH_W_ACTIVE (1 << 0) /* not ready for write */
50
51 #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
52
53 static void __iomem *regbase;
54
vt8500_timer_read(struct clocksource * cs)55 static cycle_t vt8500_timer_read(struct clocksource *cs)
56 {
57 int loops = msecs_to_loops(10);
58 writel(3, regbase + TIMER_CTRL_VAL);
59 while ((readl((regbase + TIMER_AS_VAL)) & TIMER_COUNT_R_ACTIVE)
60 && --loops)
61 cpu_relax();
62 return readl(regbase + TIMER_COUNT_VAL);
63 }
64
65 static struct clocksource clocksource = {
66 .name = "vt8500_timer",
67 .rating = 200,
68 .read = vt8500_timer_read,
69 .mask = CLOCKSOURCE_MASK(32),
70 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
71 };
72
vt8500_timer_set_next_event(unsigned long cycles,struct clock_event_device * evt)73 static int vt8500_timer_set_next_event(unsigned long cycles,
74 struct clock_event_device *evt)
75 {
76 int loops = msecs_to_loops(10);
77 cycle_t alarm = clocksource.read(&clocksource) + cycles;
78 while ((readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE)
79 && --loops)
80 cpu_relax();
81 writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL);
82
83 if ((signed)(alarm - clocksource.read(&clocksource)) <= 16)
84 return -ETIME;
85
86 writel(1, regbase + TIMER_IER_VAL);
87
88 return 0;
89 }
90
vt8500_timer_set_mode(enum clock_event_mode mode,struct clock_event_device * evt)91 static void vt8500_timer_set_mode(enum clock_event_mode mode,
92 struct clock_event_device *evt)
93 {
94 switch (mode) {
95 case CLOCK_EVT_MODE_RESUME:
96 case CLOCK_EVT_MODE_PERIODIC:
97 break;
98 case CLOCK_EVT_MODE_ONESHOT:
99 case CLOCK_EVT_MODE_UNUSED:
100 case CLOCK_EVT_MODE_SHUTDOWN:
101 writel(readl(regbase + TIMER_CTRL_VAL) | 1,
102 regbase + TIMER_CTRL_VAL);
103 writel(0, regbase + TIMER_IER_VAL);
104 break;
105 }
106 }
107
108 static struct clock_event_device clockevent = {
109 .name = "vt8500_timer",
110 .features = CLOCK_EVT_FEAT_ONESHOT,
111 .rating = 200,
112 .set_next_event = vt8500_timer_set_next_event,
113 .set_mode = vt8500_timer_set_mode,
114 };
115
vt8500_timer_interrupt(int irq,void * dev_id)116 static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
117 {
118 struct clock_event_device *evt = dev_id;
119 writel(0xf, regbase + TIMER_STATUS_VAL);
120 evt->event_handler(evt);
121
122 return IRQ_HANDLED;
123 }
124
125 static struct irqaction irq = {
126 .name = "vt8500_timer",
127 .flags = IRQF_TIMER | IRQF_IRQPOLL,
128 .handler = vt8500_timer_interrupt,
129 .dev_id = &clockevent,
130 };
131
vt8500_timer_init(struct device_node * np)132 static void __init vt8500_timer_init(struct device_node *np)
133 {
134 int timer_irq;
135
136 regbase = of_iomap(np, 0);
137 if (!regbase) {
138 pr_err("%s: Missing iobase description in Device Tree\n",
139 __func__);
140 return;
141 }
142 timer_irq = irq_of_parse_and_map(np, 0);
143 if (!timer_irq) {
144 pr_err("%s: Missing irq description in Device Tree\n",
145 __func__);
146 return;
147 }
148
149 writel(1, regbase + TIMER_CTRL_VAL);
150 writel(0xf, regbase + TIMER_STATUS_VAL);
151 writel(~0, regbase + TIMER_MATCH_VAL);
152
153 if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ))
154 pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n",
155 __func__, clocksource.name);
156
157 clockevent.cpumask = cpumask_of(0);
158
159 if (setup_irq(timer_irq, &irq))
160 pr_err("%s: setup_irq failed for %s\n", __func__,
161 clockevent.name);
162 clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ,
163 4, 0xf0000000);
164 }
165
166 CLOCKSOURCE_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init);
167