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 #define MIN_OSCR_DELTA 16
54
55 static void __iomem *regbase;
56
vt8500_timer_read(struct clocksource * cs)57 static cycle_t vt8500_timer_read(struct clocksource *cs)
58 {
59 int loops = msecs_to_loops(10);
60 writel(3, regbase + TIMER_CTRL_VAL);
61 while ((readl((regbase + TIMER_AS_VAL)) & TIMER_COUNT_R_ACTIVE)
62 && --loops)
63 cpu_relax();
64 return readl(regbase + TIMER_COUNT_VAL);
65 }
66
67 static struct clocksource clocksource = {
68 .name = "vt8500_timer",
69 .rating = 200,
70 .read = vt8500_timer_read,
71 .mask = CLOCKSOURCE_MASK(32),
72 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
73 };
74
vt8500_timer_set_next_event(unsigned long cycles,struct clock_event_device * evt)75 static int vt8500_timer_set_next_event(unsigned long cycles,
76 struct clock_event_device *evt)
77 {
78 int loops = msecs_to_loops(10);
79 cycle_t alarm = clocksource.read(&clocksource) + cycles;
80 while ((readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE)
81 && --loops)
82 cpu_relax();
83 writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL);
84
85 if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA)
86 return -ETIME;
87
88 writel(1, regbase + TIMER_IER_VAL);
89
90 return 0;
91 }
92
vt8500_shutdown(struct clock_event_device * evt)93 static int vt8500_shutdown(struct clock_event_device *evt)
94 {
95 writel(readl(regbase + TIMER_CTRL_VAL) | 1, regbase + TIMER_CTRL_VAL);
96 writel(0, regbase + TIMER_IER_VAL);
97 return 0;
98 }
99
100 static struct clock_event_device clockevent = {
101 .name = "vt8500_timer",
102 .features = CLOCK_EVT_FEAT_ONESHOT,
103 .rating = 200,
104 .set_next_event = vt8500_timer_set_next_event,
105 .set_state_shutdown = vt8500_shutdown,
106 .set_state_oneshot = vt8500_shutdown,
107 };
108
vt8500_timer_interrupt(int irq,void * dev_id)109 static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
110 {
111 struct clock_event_device *evt = dev_id;
112 writel(0xf, regbase + TIMER_STATUS_VAL);
113 evt->event_handler(evt);
114
115 return IRQ_HANDLED;
116 }
117
118 static struct irqaction irq = {
119 .name = "vt8500_timer",
120 .flags = IRQF_TIMER | IRQF_IRQPOLL,
121 .handler = vt8500_timer_interrupt,
122 .dev_id = &clockevent,
123 };
124
vt8500_timer_init(struct device_node * np)125 static void __init vt8500_timer_init(struct device_node *np)
126 {
127 int timer_irq;
128
129 regbase = of_iomap(np, 0);
130 if (!regbase) {
131 pr_err("%s: Missing iobase description in Device Tree\n",
132 __func__);
133 return;
134 }
135 timer_irq = irq_of_parse_and_map(np, 0);
136 if (!timer_irq) {
137 pr_err("%s: Missing irq description in Device Tree\n",
138 __func__);
139 return;
140 }
141
142 writel(1, regbase + TIMER_CTRL_VAL);
143 writel(0xf, regbase + TIMER_STATUS_VAL);
144 writel(~0, regbase + TIMER_MATCH_VAL);
145
146 if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ))
147 pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n",
148 __func__, clocksource.name);
149
150 clockevent.cpumask = cpumask_of(0);
151
152 if (setup_irq(timer_irq, &irq))
153 pr_err("%s: setup_irq failed for %s\n", __func__,
154 clockevent.name);
155 clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ,
156 MIN_OSCR_DELTA * 2, 0xf0000000);
157 }
158
159 CLOCKSOURCE_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init);
160