Linux Kernel  3.7.1
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timer.c
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1 /*
2  * arch/arm/mach-vt8500/timer_dt.c
3  *
4  * Copyright (C) 2012 Tony Prisk <[email protected]>
5  * Copyright (C) 2010 Alexey Charkov <[email protected]>
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 
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),
71 };
72 
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 
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 
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",
128  .handler = vt8500_timer_interrupt,
129  .dev_id = &clockevent,
130 };
131 
132 static struct of_device_id vt8500_timer_ids[] = {
133  { .compatible = "via,vt8500-timer" },
134  { }
135 };
136 
138 {
139  struct device_node *np;
140  int timer_irq;
141 
142  np = of_find_matching_node(NULL, vt8500_timer_ids);
143  if (!np) {
144  pr_err("%s: Timer description missing from Device Tree\n",
145  __func__);
146  return;
147  }
148  regbase = of_iomap(np, 0);
149  if (!regbase) {
150  pr_err("%s: Missing iobase description in Device Tree\n",
151  __func__);
152  of_node_put(np);
153  return;
154  }
155  timer_irq = irq_of_parse_and_map(np, 0);
156  if (!timer_irq) {
157  pr_err("%s: Missing irq description in Device Tree\n",
158  __func__);
159  of_node_put(np);
160  return;
161  }
162 
163  writel(1, regbase + TIMER_CTRL_VAL);
164  writel(0xf, regbase + TIMER_STATUS_VAL);
165  writel(~0, regbase + TIMER_MATCH_VAL);
166 
167  if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ))
168  pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n",
169  __func__, clocksource.name);
170 
171  clockevents_calc_mult_shift(&clockevent, VT8500_TIMER_HZ, 4);
172 
173  /* copy-pasted from mach-msm; no idea */
174  clockevent.max_delta_ns =
175  clockevent_delta2ns(0xf0000000, &clockevent);
176  clockevent.min_delta_ns = clockevent_delta2ns(4, &clockevent);
177  clockevent.cpumask = cpumask_of(0);
178 
179  if (setup_irq(timer_irq, &irq))
180  pr_err("%s: setup_irq failed for %s\n", __func__,
181  clockevent.name);
182  clockevents_register_device(&clockevent);
183 }
184