aboutsummaryrefslogtreecommitdiff
path: root/arch/arm/plat-spear/time.c
blob: 0c77e42986758554bc25931cc6ed88287353a9b9 (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
/*
 * arch/arm/plat-spear/time.c
 *
 * Copyright (C) 2010 ST Microelectronics
 * Shiraz Hashim<shiraz.hashim@st.com>
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/clk.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/time.h>
#include <linux/irq.h>
#include <asm/mach/time.h>
#include <mach/generic.h>
#include <mach/hardware.h>
#include <mach/irqs.h>

/*
 * We would use TIMER0 and TIMER1 as clockevent and clocksource.
 * Timer0 and Timer1 both belong to same gpt block in cpu subbsystem. Further
 * they share same functional clock. Any change in one's functional clock will
 * also affect other timer.
 */

#define CLKEVT	0	/* gpt0, channel0 as clockevent */
#define CLKSRC	1	/* gpt0, channel1 as clocksource */

/* Register offsets, x is channel number */
#define CR(x)		((x) * 0x80 + 0x80)
#define IR(x)		((x) * 0x80 + 0x84)
#define LOAD(x)		((x) * 0x80 + 0x88)
#define COUNT(x)	((x) * 0x80 + 0x8C)

/* Reg bit definitions */
#define CTRL_INT_ENABLE		0x0100
#define CTRL_ENABLE		0x0020
#define CTRL_ONE_SHOT		0x0010

#define CTRL_PRESCALER1		0x0
#define CTRL_PRESCALER2		0x1
#define CTRL_PRESCALER4		0x2
#define CTRL_PRESCALER8		0x3
#define CTRL_PRESCALER16	0x4
#define CTRL_PRESCALER32	0x5
#define CTRL_PRESCALER64	0x6
#define CTRL_PRESCALER128	0x7
#define CTRL_PRESCALER256	0x8

#define INT_STATUS		0x1

/*
 * Minimum clocksource/clockevent timer range in seconds
 */
#define SPEAR_MIN_RANGE 4

static __iomem void *gpt_base;
static struct clk *gpt_clk;

static void clockevent_set_mode(enum clock_event_mode mode,
				struct clock_event_device *clk_event_dev);
static int clockevent_next_event(unsigned long evt,
				 struct clock_event_device *clk_event_dev);

static void spear_clocksource_init(void)
{
	u32 tick_rate;
	u16 val;

	/* program the prescaler (/256)*/
	writew(CTRL_PRESCALER256, gpt_base + CR(CLKSRC));

	/* find out actual clock driving Timer */
	tick_rate = clk_get_rate(gpt_clk);
	tick_rate >>= CTRL_PRESCALER256;

	writew(0xFFFF, gpt_base + LOAD(CLKSRC));

	val = readw(gpt_base + CR(CLKSRC));
	val &= ~CTRL_ONE_SHOT;	/* autoreload mode */
	val |= CTRL_ENABLE ;
	writew(val, gpt_base + CR(CLKSRC));

	/* register the clocksource */
	clocksource_mmio_init(gpt_base + COUNT(CLKSRC), "tmr1", tick_rate,
		200, 16, clocksource_mmio_readw_up);
}

static struct clock_event_device clkevt = {
	.name = "tmr0",
	.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
	.set_mode = clockevent_set_mode,
	.set_next_event = clockevent_next_event,
	.shift = 0,	/* to be computed */
};

static void clockevent_set_mode(enum clock_event_mode mode,
				struct clock_event_device *clk_event_dev)
{
	u32 period;
	u16 val;

	/* stop the timer */
	val = readw(gpt_base + CR(CLKEVT));
	val &= ~CTRL_ENABLE;
	writew(val, gpt_base + CR(CLKEVT));

	switch (mode) {
	case CLOCK_EVT_MODE_PERIODIC:
		period = clk_get_rate(gpt_clk) / HZ;
		period >>= CTRL_PRESCALER16;
		writew(period, gpt_base + LOAD(CLKEVT));

		val = readw(gpt_base + CR(CLKEVT));
		val &= ~CTRL_ONE_SHOT;
		val |= CTRL_ENABLE | CTRL_INT_ENABLE;
		writew(val, gpt_base + CR(CLKEVT));

		break;
	case CLOCK_EVT_MODE_ONESHOT:
		val = readw(gpt_base + CR(CLKEVT));
		val |= CTRL_ONE_SHOT;
		writew(val, gpt_base + CR(CLKEVT));

		break;
	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
	case CLOCK_EVT_MODE_RESUME:

		break;
	default:
		pr_err("Invalid mode requested\n");
		break;
	}
}

static int clockevent_next_event(unsigned long cycles,
				 struct clock_event_device *clk_event_dev)
{
	u16 val;

	writew(cycles, gpt_base + LOAD(CLKEVT));

	val = readw(gpt_base + CR(CLKEVT));
	val |= CTRL_ENABLE | CTRL_INT_ENABLE;
	writew(val, gpt_base + CR(CLKEVT));

	return 0;
}

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

	writew(INT_STATUS, gpt_base + IR(CLKEVT));

	evt->event_handler(evt);

	return IRQ_HANDLED;
}

static struct irqaction spear_timer_irq = {
	.name = "timer",
	.flags = IRQF_DISABLED | IRQF_TIMER,
	.handler = spear_timer_interrupt
};

static void __init spear_clockevent_init(void)
{
	u32 tick_rate;

	/* program the prescaler */
	writew(CTRL_PRESCALER16, gpt_base + CR(CLKEVT));

	tick_rate = clk_get_rate(gpt_clk);
	tick_rate >>= CTRL_PRESCALER16;

	clockevents_calc_mult_shift(&clkevt, tick_rate, SPEAR_MIN_RANGE);

	clkevt.max_delta_ns = clockevent_delta2ns(0xfff0,
			&clkevt);
	clkevt.min_delta_ns = clockevent_delta2ns(3, &clkevt);

	clkevt.cpumask = cpumask_of(0);

	clockevents_register_device(&clkevt);

	setup_irq(SPEAR_GPT0_CHAN0_IRQ, &spear_timer_irq);
}

void __init spear_setup_timer(void)
{
	int ret;

	if (!request_mem_region(SPEAR_GPT0_BASE, SZ_1K, "gpt0")) {
		pr_err("%s:cannot get IO addr\n", __func__);
		return;
	}

	gpt_base = (void __iomem *)ioremap(SPEAR_GPT0_BASE, SZ_1K);
	if (!gpt_base) {
		pr_err("%s:ioremap failed for gpt\n", __func__);
		goto err_mem;
	}

	gpt_clk = clk_get_sys("gpt0", NULL);
	if (!gpt_clk) {
		pr_err("%s:couldn't get clk for gpt\n", __func__);
		goto err_iomap;
	}

	ret = clk_enable(gpt_clk);
	if (ret < 0) {
		pr_err("%s:couldn't enable gpt clock\n", __func__);
		goto err_clk;
	}

	spear_clockevent_init();
	spear_clocksource_init();

	return;

err_clk:
	clk_put(gpt_clk);
err_iomap:
	iounmap(gpt_base);
err_mem:
	release_mem_region(SPEAR_GPT0_BASE, SZ_1K);
}