tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
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
53static void __iomem *regbase;
54
55static 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
65static 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
73static 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
91static int vt8500_shutdown(struct clock_event_device *evt)
92{
93 writel(readl(regbase + TIMER_CTRL_VAL) | 1, regbase + TIMER_CTRL_VAL);
94 writel(0, regbase + TIMER_IER_VAL);
95 return 0;
96}
97
98static struct clock_event_device clockevent = {
99 .name = "vt8500_timer",
100 .features = CLOCK_EVT_FEAT_ONESHOT,
101 .rating = 200,
102 .set_next_event = vt8500_timer_set_next_event,
103 .set_state_shutdown = vt8500_shutdown,
104 .set_state_oneshot = vt8500_shutdown,
105};
106
107static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
108{
109 struct clock_event_device *evt = dev_id;
110 writel(0xf, regbase + TIMER_STATUS_VAL);
111 evt->event_handler(evt);
112
113 return IRQ_HANDLED;
114}
115
116static struct irqaction irq = {
117 .name = "vt8500_timer",
118 .flags = IRQF_TIMER | IRQF_IRQPOLL,
119 .handler = vt8500_timer_interrupt,
120 .dev_id = &clockevent,
121};
122
123static void __init vt8500_timer_init(struct device_node *np)
124{
125 int timer_irq;
126
127 regbase = of_iomap(np, 0);
128 if (!regbase) {
129 pr_err("%s: Missing iobase description in Device Tree\n",
130 __func__);
131 return;
132 }
133 timer_irq = irq_of_parse_and_map(np, 0);
134 if (!timer_irq) {
135 pr_err("%s: Missing irq description in Device Tree\n",
136 __func__);
137 return;
138 }
139
140 writel(1, regbase + TIMER_CTRL_VAL);
141 writel(0xf, regbase + TIMER_STATUS_VAL);
142 writel(~0, regbase + TIMER_MATCH_VAL);
143
144 if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ))
145 pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n",
146 __func__, clocksource.name);
147
148 clockevent.cpumask = cpumask_of(0);
149
150 if (setup_irq(timer_irq, &irq))
151 pr_err("%s: setup_irq failed for %s\n", __func__,
152 clockevent.name);
153 clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ,
154 4, 0xf0000000);
155}
156
157CLOCKSOURCE_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init);