aboutsummaryrefslogtreecommitdiffstats
path: root/arch/arm/kernel/smp_twd.c
blob: 7a79b24597b2d51953826338e13656803fe9c229 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
/*
 *  linux/arch/arm/kernel/smp_twd.c
 *
 *  Copyright (C) 2002 ARM Ltd.
 *  All Rights Reserved
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/smp.h>
#include <linux/jiffies.h>
#include <linux/clockchips.h>
#include <linux/irq.h>
#include <linux/io.h>

#include <asm/smp_twd.h>
#include <asm/localtimer.h>
#include <asm/hardware/gic.h>

/* set up by the platform code */
void __iomem *twd_base;

static struct clk *twd_clk;
static unsigned long twd_timer_rate;

static struct clock_event_device __percpu **twd_evt;

static void twd_set_mode(enum clock_event_mode mode,
			struct clock_event_device *clk)
{
	unsigned long ctrl;

	switch (mode) {
	case CLOCK_EVT_MODE_PERIODIC:
		/* timer load already set up */
		ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
			| TWD_TIMER_CONTROL_PERIODIC;
		__raw_writel(twd_timer_rate / HZ, twd_base + TWD_TIMER_LOAD);
		break;
	case CLOCK_EVT_MODE_ONESHOT:
		/* period set, and timer enabled in 'next_event' hook */
		ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
		break;
	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
	default:
		ctrl = 0;
	}

	__raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
}

static int twd_set_next_event(unsigned long evt,
			struct clock_event_device *unused)
{
	unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);

	ctrl |= TWD_TIMER_CONTROL_ENABLE;

	__raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
	__raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);

	return 0;
}

/*
 * local_timer_ack: checks for a local timer interrupt.
 *
 * If a local timer interrupt has occurred, acknowledge and return 1.
 * Otherwise, return 0.
 */
int twd_timer_ack(void)
{
	if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
		__raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
		return 1;
	}

	return 0;
}

void twd_timer_stop(struct clock_event_device *clk)
{
	twd_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
	disable_percpu_irq(clk->irq);
}

#ifdef CONFIG_CPU_FREQ

/*
 * Updates clockevent frequency when the cpu frequency changes.
 * Called on the cpu that is changing frequency with interrupts disabled.
 */
static void twd_update_frequency(void *data)
{
	twd_timer_rate = clk_get_rate(twd_clk);

	clockevents_update_freq(*__this_cpu_ptr(twd_evt), twd_timer_rate);
}

static int twd_cpufreq_transition(struct notifier_block *nb,
	unsigned long state, void *data)
{
	struct cpufreq_freqs *freqs = data;

	/*
	 * The twd clock events must be reprogrammed to account for the new
	 * frequency.  The timer is local to a cpu, so cross-call to the
	 * changing cpu.
	 */
	if (state == CPUFREQ_POSTCHANGE || state == CPUFREQ_RESUMECHANGE)
		smp_call_function_single(freqs->cpu, twd_update_frequency,
			NULL, 1);

	return NOTIFY_OK;
}

static struct notifier_block twd_cpufreq_nb = {
	.notifier_call = twd_cpufreq_transition,
};

static int twd_cpufreq_init(void)
{
	if (twd_evt && *__this_cpu_ptr(twd_evt) && !IS_ERR(twd_clk))
		return cpufreq_register_notifier(&twd_cpufreq_nb,
			CPUFREQ_TRANSITION_NOTIFIER);

	return 0;
}
core_initcall(twd_cpufreq_init);

#endif

static void __cpuinit twd_calibrate_rate(void)
{
	unsigned long count;
	u64 waitjiffies;

	/*
	 * If this is the first time round, we need to work out how fast
	 * the timer ticks
	 */
	if (twd_timer_rate == 0) {
		printk(KERN_INFO "Calibrating local timer... ");

		/* Wait for a tick to start */
		waitjiffies = get_jiffies_64() + 1;

		while (get_jiffies_64() < waitjiffies)
			udelay(10);

		/* OK, now the tick has started, let's get the timer going */
		waitjiffies += 5;

				 /* enable, no interrupt or reload */
		__raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);

				 /* maximum value */
		__raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);

		while (get_jiffies_64() < waitjiffies)
			udelay(10);

		count = __raw_readl(twd_base + TWD_TIMER_COUNTER);

		twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);

		printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
			(twd_timer_rate / 10000) % 100);
	}
}

static irqreturn_t twd_handler(int irq, void *dev_id)
{
	struct clock_event_device *evt = *(struct clock_event_device **)dev_id;

	if (twd_timer_ack()) {
		evt->event_handler(evt);
		return IRQ_HANDLED;
	}

	return IRQ_NONE;
}

static struct clk *twd_get_clock(void)
{
	struct clk *clk;
	int err;

	clk = clk_get_sys("smp_twd", NULL);
	if (IS_ERR(clk)) {
		pr_err("smp_twd: clock not found: %d\n", (int)PTR_ERR(clk));
		return clk;
	}

	err = clk_prepare(clk);
	if (err) {
		pr_err("smp_twd: clock failed to prepare: %d\n", err);
		clk_put(clk);
		return ERR_PTR(err);
	}

	err = clk_enable(clk);
	if (err) {
		pr_err("smp_twd: clock failed to enable: %d\n", err);
		clk_unprepare(clk);
		clk_put(clk);
		return ERR_PTR(err);
	}

	return clk;
}

/*
 * Setup the local clock events for a CPU.
 */
void __cpuinit twd_timer_setup(struct clock_event_device *clk)
{
	struct clock_event_device **this_cpu_clk;

	if (!twd_evt) {
		int err;

		twd_evt = alloc_percpu(struct clock_event_device *);
		if (!twd_evt) {
			pr_err("twd: can't allocate memory\n");
			return;
		}

		err = request_percpu_irq(clk->irq, twd_handler,
					 "twd", twd_evt);
		if (err) {
			pr_err("twd: can't register interrupt %d (%d)\n",
			       clk->irq, err);
			return;
		}
	}

	if (!twd_clk)
		twd_clk = twd_get_clock();

	if (!IS_ERR_OR_NULL(twd_clk))
		twd_timer_rate = clk_get_rate(twd_clk);
	else
		twd_calibrate_rate();

	__raw_writel(0, twd_base + TWD_TIMER_CONTROL);

	clk->name = "local_timer";
	clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
			CLOCK_EVT_FEAT_C3STOP;
	clk->rating = 350;
	clk->set_mode = twd_set_mode;
	clk->set_next_event = twd_set_next_event;

	this_cpu_clk = __this_cpu_ptr(twd_evt);
	*this_cpu_clk = clk;

	clockevents_config_and_register(clk, twd_timer_rate,
					0xf, 0xffffffff);
	enable_percpu_irq(clk->irq, 0);
}