summaryrefslogtreecommitdiff
path: root/arch/arm/mach-u300/timer.c
blob: 6c68fe7979035b99c7639786c0eecc917060071c (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
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
/*
 *
 * arch/arm/mach-u300/timer.c
 *
 *
 * Copyright (C) 2007-2009 ST-Ericsson AB
 * License terms: GNU General Public License (GPL) version 2
 * Timer COH 901 328, runs the OS timer interrupt.
 * Author: Linus Walleij <linus.walleij@stericsson.com>
 */
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/types.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/err.h>

#include <mach/hardware.h>

/* Generic stuff */
#include <asm/mach/map.h>
#include <asm/mach/time.h>
#include <asm/mach/irq.h>

/* Be able to sleep for atleast 4 seconds (usually more) */
#define APPTIMER_MIN_RANGE 4

/*
 * APP side special timer registers
 * This timer contains four timers which can fire an interrupt each.
 * OS (operating system) timer @ 32768 Hz
 * DD (device driver) timer @ 1 kHz
 * GP1 (general purpose 1) timer @ 1MHz
 * GP2 (general purpose 2) timer @ 1MHz
 */

/* Reset OS Timer 32bit (-/W) */
#define U300_TIMER_APP_ROST					(0x0000)
#define U300_TIMER_APP_ROST_TIMER_RESET				(0x00000000)
/* Enable OS Timer 32bit (-/W) */
#define U300_TIMER_APP_EOST					(0x0004)
#define U300_TIMER_APP_EOST_TIMER_ENABLE			(0x00000000)
/* Disable OS Timer 32bit (-/W) */
#define U300_TIMER_APP_DOST					(0x0008)
#define U300_TIMER_APP_DOST_TIMER_DISABLE			(0x00000000)
/* OS Timer Mode Register 32bit (-/W) */
#define U300_TIMER_APP_SOSTM					(0x000c)
#define U300_TIMER_APP_SOSTM_MODE_CONTINUOUS			(0x00000000)
#define U300_TIMER_APP_SOSTM_MODE_ONE_SHOT			(0x00000001)
/* OS Timer Status Register 32bit (R/-) */
#define U300_TIMER_APP_OSTS					(0x0010)
#define U300_TIMER_APP_OSTS_TIMER_STATE_MASK			(0x0000000F)
#define U300_TIMER_APP_OSTS_TIMER_STATE_IDLE			(0x00000001)
#define U300_TIMER_APP_OSTS_TIMER_STATE_ACTIVE			(0x00000002)
#define U300_TIMER_APP_OSTS_ENABLE_IND				(0x00000010)
#define U300_TIMER_APP_OSTS_MODE_MASK				(0x00000020)
#define U300_TIMER_APP_OSTS_MODE_CONTINUOUS			(0x00000000)
#define U300_TIMER_APP_OSTS_MODE_ONE_SHOT			(0x00000020)
#define U300_TIMER_APP_OSTS_IRQ_ENABLED_IND			(0x00000040)
#define U300_TIMER_APP_OSTS_IRQ_PENDING_IND			(0x00000080)
/* OS Timer Current Count Register 32bit (R/-) */
#define U300_TIMER_APP_OSTCC					(0x0014)
/* OS Timer Terminal Count Register 32bit (R/W) */
#define U300_TIMER_APP_OSTTC					(0x0018)
/* OS Timer Interrupt Enable Register 32bit (-/W) */
#define U300_TIMER_APP_OSTIE					(0x001c)
#define U300_TIMER_APP_OSTIE_IRQ_DISABLE			(0x00000000)
#define U300_TIMER_APP_OSTIE_IRQ_ENABLE				(0x00000001)
/* OS Timer Interrupt Acknowledge Register 32bit (-/W) */
#define U300_TIMER_APP_OSTIA					(0x0020)
#define U300_TIMER_APP_OSTIA_IRQ_ACK				(0x00000080)

/* Reset DD Timer 32bit (-/W) */
#define U300_TIMER_APP_RDDT					(0x0040)
#define U300_TIMER_APP_RDDT_TIMER_RESET				(0x00000000)
/* Enable DD Timer 32bit (-/W) */
#define U300_TIMER_APP_EDDT					(0x0044)
#define U300_TIMER_APP_EDDT_TIMER_ENABLE			(0x00000000)
/* Disable DD Timer 32bit (-/W) */
#define U300_TIMER_APP_DDDT					(0x0048)
#define U300_TIMER_APP_DDDT_TIMER_DISABLE			(0x00000000)
/* DD Timer Mode Register 32bit (-/W) */
#define U300_TIMER_APP_SDDTM					(0x004c)
#define U300_TIMER_APP_SDDTM_MODE_CONTINUOUS			(0x00000000)
#define U300_TIMER_APP_SDDTM_MODE_ONE_SHOT			(0x00000001)
/* DD Timer Status Register 32bit (R/-) */
#define U300_TIMER_APP_DDTS					(0x0050)
#define U300_TIMER_APP_DDTS_TIMER_STATE_MASK			(0x0000000F)
#define U300_TIMER_APP_DDTS_TIMER_STATE_IDLE			(0x00000001)
#define U300_TIMER_APP_DDTS_TIMER_STATE_ACTIVE			(0x00000002)
#define U300_TIMER_APP_DDTS_ENABLE_IND				(0x00000010)
#define U300_TIMER_APP_DDTS_MODE_MASK				(0x00000020)
#define U300_TIMER_APP_DDTS_MODE_CONTINUOUS			(0x00000000)
#define U300_TIMER_APP_DDTS_MODE_ONE_SHOT			(0x00000020)
#define U300_TIMER_APP_DDTS_IRQ_ENABLED_IND			(0x00000040)
#define U300_TIMER_APP_DDTS_IRQ_PENDING_IND			(0x00000080)
/* DD Timer Current Count Register 32bit (R/-) */
#define U300_TIMER_APP_DDTCC					(0x0054)
/* DD Timer Terminal Count Register 32bit (R/W) */
#define U300_TIMER_APP_DDTTC					(0x0058)
/* DD Timer Interrupt Enable Register 32bit (-/W) */
#define U300_TIMER_APP_DDTIE					(0x005c)
#define U300_TIMER_APP_DDTIE_IRQ_DISABLE			(0x00000000)
#define U300_TIMER_APP_DDTIE_IRQ_ENABLE				(0x00000001)
/* DD Timer Interrupt Acknowledge Register 32bit (-/W) */
#define U300_TIMER_APP_DDTIA					(0x0060)
#define U300_TIMER_APP_DDTIA_IRQ_ACK				(0x00000080)

/* Reset GP1 Timer 32bit (-/W) */
#define U300_TIMER_APP_RGPT1					(0x0080)
#define U300_TIMER_APP_RGPT1_TIMER_RESET			(0x00000000)
/* Enable GP1 Timer 32bit (-/W) */
#define U300_TIMER_APP_EGPT1					(0x0084)
#define U300_TIMER_APP_EGPT1_TIMER_ENABLE			(0x00000000)
/* Disable GP1 Timer 32bit (-/W) */
#define U300_TIMER_APP_DGPT1					(0x0088)
#define U300_TIMER_APP_DGPT1_TIMER_DISABLE			(0x00000000)
/* GP1 Timer Mode Register 32bit (-/W) */
#define U300_TIMER_APP_SGPT1M					(0x008c)
#define U300_TIMER_APP_SGPT1M_MODE_CONTINUOUS			(0x00000000)
#define U300_TIMER_APP_SGPT1M_MODE_ONE_SHOT			(0x00000001)
/* GP1 Timer Status Register 32bit (R/-) */
#define U300_TIMER_APP_GPT1S					(0x0090)
#define U300_TIMER_APP_GPT1S_TIMER_STATE_MASK			(0x0000000F)
#define U300_TIMER_APP_GPT1S_TIMER_STATE_IDLE			(0x00000001)
#define U300_TIMER_APP_GPT1S_TIMER_STATE_ACTIVE			(0x00000002)
#define U300_TIMER_APP_GPT1S_ENABLE_IND				(0x00000010)
#define U300_TIMER_APP_GPT1S_MODE_MASK				(0x00000020)
#define U300_TIMER_APP_GPT1S_MODE_CONTINUOUS			(0x00000000)
#define U300_TIMER_APP_GPT1S_MODE_ONE_SHOT			(0x00000020)
#define U300_TIMER_APP_GPT1S_IRQ_ENABLED_IND			(0x00000040)
#define U300_TIMER_APP_GPT1S_IRQ_PENDING_IND			(0x00000080)
/* GP1 Timer Current Count Register 32bit (R/-) */
#define U300_TIMER_APP_GPT1CC					(0x0094)
/* GP1 Timer Terminal Count Register 32bit (R/W) */
#define U300_TIMER_APP_GPT1TC					(0x0098)
/* GP1 Timer Interrupt Enable Register 32bit (-/W) */
#define U300_TIMER_APP_GPT1IE					(0x009c)
#define U300_TIMER_APP_GPT1IE_IRQ_DISABLE			(0x00000000)
#define U300_TIMER_APP_GPT1IE_IRQ_ENABLE			(0x00000001)
/* GP1 Timer Interrupt Acknowledge Register 32bit (-/W) */
#define U300_TIMER_APP_GPT1IA					(0x00a0)
#define U300_TIMER_APP_GPT1IA_IRQ_ACK				(0x00000080)

/* Reset GP2 Timer 32bit (-/W) */
#define U300_TIMER_APP_RGPT2					(0x00c0)
#define U300_TIMER_APP_RGPT2_TIMER_RESET			(0x00000000)
/* Enable GP2 Timer 32bit (-/W) */
#define U300_TIMER_APP_EGPT2					(0x00c4)
#define U300_TIMER_APP_EGPT2_TIMER_ENABLE			(0x00000000)
/* Disable GP2 Timer 32bit (-/W) */
#define U300_TIMER_APP_DGPT2					(0x00c8)
#define U300_TIMER_APP_DGPT2_TIMER_DISABLE			(0x00000000)
/* GP2 Timer Mode Register 32bit (-/W) */
#define U300_TIMER_APP_SGPT2M					(0x00cc)
#define U300_TIMER_APP_SGPT2M_MODE_CONTINUOUS			(0x00000000)
#define U300_TIMER_APP_SGPT2M_MODE_ONE_SHOT			(0x00000001)
/* GP2 Timer Status Register 32bit (R/-) */
#define U300_TIMER_APP_GPT2S					(0x00d0)
#define U300_TIMER_APP_GPT2S_TIMER_STATE_MASK			(0x0000000F)
#define U300_TIMER_APP_GPT2S_TIMER_STATE_IDLE			(0x00000001)
#define U300_TIMER_APP_GPT2S_TIMER_STATE_ACTIVE			(0x00000002)
#define U300_TIMER_APP_GPT2S_ENABLE_IND				(0x00000010)
#define U300_TIMER_APP_GPT2S_MODE_MASK				(0x00000020)
#define U300_TIMER_APP_GPT2S_MODE_CONTINUOUS			(0x00000000)
#define U300_TIMER_APP_GPT2S_MODE_ONE_SHOT			(0x00000020)
#define U300_TIMER_APP_GPT2S_IRQ_ENABLED_IND			(0x00000040)
#define U300_TIMER_APP_GPT2S_IRQ_PENDING_IND			(0x00000080)
/* GP2 Timer Current Count Register 32bit (R/-) */
#define U300_TIMER_APP_GPT2CC					(0x00d4)
/* GP2 Timer Terminal Count Register 32bit (R/W) */
#define U300_TIMER_APP_GPT2TC					(0x00d8)
/* GP2 Timer Interrupt Enable Register 32bit (-/W) */
#define U300_TIMER_APP_GPT2IE					(0x00dc)
#define U300_TIMER_APP_GPT2IE_IRQ_DISABLE			(0x00000000)
#define U300_TIMER_APP_GPT2IE_IRQ_ENABLE			(0x00000001)
/* GP2 Timer Interrupt Acknowledge Register 32bit (-/W) */
#define U300_TIMER_APP_GPT2IA					(0x00e0)
#define U300_TIMER_APP_GPT2IA_IRQ_ACK				(0x00000080)

/* Clock request control register - all four timers */
#define U300_TIMER_APP_CRC					(0x100)
#define U300_TIMER_APP_CRC_CLOCK_REQUEST_ENABLE			(0x00000001)

#define TICKS_PER_JIFFY ((CLOCK_TICK_RATE + (HZ/2)) / HZ)
#define US_PER_TICK ((1000000 + (HZ/2)) / HZ)

/*
 * The u300_set_mode() function is always called first, if we
 * have oneshot timer active, the oneshot scheduling function
 * u300_set_next_event() is called immediately after.
 */
static void u300_set_mode(enum clock_event_mode mode,
			  struct clock_event_device *evt)
{
	switch (mode) {
	case CLOCK_EVT_MODE_PERIODIC:
		/* Disable interrupts on GPT1 */
		writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
		/* Disable GP1 while we're reprogramming it. */
		writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_DGPT1);
		/*
		 * Set the periodic mode to a certain number of ticks per
		 * jiffy.
		 */
		writel(TICKS_PER_JIFFY,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1TC);
		/*
		 * Set continuous mode, so the timer keeps triggering
		 * interrupts.
		 */
		writel(U300_TIMER_APP_SGPT1M_MODE_CONTINUOUS,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_SGPT1M);
		/* Enable timer interrupts */
		writel(U300_TIMER_APP_GPT1IE_IRQ_ENABLE,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
		/* Then enable the OS timer again */
		writel(U300_TIMER_APP_EGPT1_TIMER_ENABLE,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_EGPT1);
		break;
	case CLOCK_EVT_MODE_ONESHOT:
		/* Just break; here? */
		/*
		 * The actual event will be programmed by the next event hook,
		 * so we just set a dummy value somewhere at the end of the
		 * universe here.
		 */
		/* Disable interrupts on GPT1 */
		writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
		/* Disable GP1 while we're reprogramming it. */
		writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_DGPT1);
		/*
		 * Expire far in the future, u300_set_next_event() will be
		 * called soon...
		 */
		writel(0xFFFFFFFF, U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1TC);
		/* We run one shot per tick here! */
		writel(U300_TIMER_APP_SGPT1M_MODE_ONE_SHOT,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_SGPT1M);
		/* Enable interrupts for this timer */
		writel(U300_TIMER_APP_GPT1IE_IRQ_ENABLE,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
		/* Enable timer */
		writel(U300_TIMER_APP_EGPT1_TIMER_ENABLE,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_EGPT1);
		break;
	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
		/* Disable interrupts on GP1 */
		writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
		/* Disable GP1 */
		writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
		       U300_TIMER_APP_VBASE + U300_TIMER_APP_DGPT1);
		break;
	case CLOCK_EVT_MODE_RESUME:
		/* Ignore this call */
		break;
	}
}

/*
 * The app timer in one shot mode obviously has to be reprogrammed
 * in EXACTLY this sequence to work properly. Do NOT try to e.g. replace
 * the interrupt disable + timer disable commands with a reset command,
 * it will fail miserably. Apparently (and I found this the hard way)
 * the timer is very sensitive to the instruction order, though you don't
 * get that impression from the data sheet.
 */
static int u300_set_next_event(unsigned long cycles,
			       struct clock_event_device *evt)

{
	/* Disable interrupts on GPT1 */
	writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
	       U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
	/* Disable GP1 while we're reprogramming it. */
	writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
	       U300_TIMER_APP_VBASE + U300_TIMER_APP_DGPT1);
	/* Reset the General Purpose timer 1. */
	writel(U300_TIMER_APP_RGPT1_TIMER_RESET,
	       U300_TIMER_APP_VBASE + U300_TIMER_APP_RGPT1);
	/* IRQ in n * cycles */
	writel(cycles, U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1TC);
	/*
	 * We run one shot per tick here! (This is necessary to reconfigure,
	 * the timer will tilt if you don't!)
	 */
	writel(U300_TIMER_APP_SGPT1M_MODE_ONE_SHOT,
	       U300_TIMER_APP_VBASE + U300_TIMER_APP_SGPT1M);
	/* Enable timer interrupts */
	writel(U300_TIMER_APP_GPT1IE_IRQ_ENABLE,
	       U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
	/* Then enable the OS timer again */
	writel(U300_TIMER_APP_EGPT1_TIMER_ENABLE,
	       U300_TIMER_APP_VBASE + U300_TIMER_APP_EGPT1);
	return 0;
}


/* Use general purpose timer 1 as clock event */
static struct clock_event_device clockevent_u300_1mhz = {
	.name           = "GPT1",
	.rating         = 300, /* Reasonably fast and accurate clock event */
	.features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
	.set_next_event = u300_set_next_event,
	.set_mode       = u300_set_mode,
};

/* Clock event timer interrupt handler */
static irqreturn_t u300_timer_interrupt(int irq, void *dev_id)
{
	struct clock_event_device *evt = &clockevent_u300_1mhz;
	/* ACK/Clear timer IRQ for the APP GPT1 Timer */
	writel(U300_TIMER_APP_GPT1IA_IRQ_ACK,
		U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IA);
	evt->event_handler(evt);
	return IRQ_HANDLED;
}

static struct irqaction u300_timer_irq = {
	.name           = "U300 Timer Tick",
	.flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
	.handler        = u300_timer_interrupt,
};

/* Use general purpose timer 2 as clock source */
static cycle_t u300_get_cycles(struct clocksource *cs)
{
	return (cycles_t) readl(U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT2CC);
}

static struct clocksource clocksource_u300_1mhz = {
	.name           = "GPT2",
	.rating         = 300, /* Reasonably fast and accurate clock source */
	.read           = u300_get_cycles,
	.mask           = CLOCKSOURCE_MASK(32), /* 32 bits */
	.flags          = CLOCK_SOURCE_IS_CONTINUOUS,
};

/*
 * Override the global weak sched_clock symbol with this
 * local implementation which uses the clocksource to get some
 * better resolution when scheduling the kernel. We accept that
 * this wraps around for now, since it is just a relative time
 * stamp. (Inspired by OMAP implementation.)
 */
unsigned long long notrace sched_clock(void)
{
	return clocksource_cyc2ns(clocksource_u300_1mhz.read(
				  &clocksource_u300_1mhz),
				  clocksource_u300_1mhz.mult,
				  clocksource_u300_1mhz.shift);
}


/*
 * This sets up the system timers, clock source and clock event.
 */
static void __init u300_timer_init(void)
{
	struct clk *clk;
	unsigned long rate;

	/* Clock the interrupt controller */
	clk = clk_get_sys("apptimer", NULL);
	BUG_ON(IS_ERR(clk));
	clk_enable(clk);
	rate = clk_get_rate(clk);

	/*
	 * Disable the "OS" and "DD" timers - these are designed for Symbian!
	 * Example usage in cnh1601578 cpu subsystem pd_timer_app.c
	 */
	writel(U300_TIMER_APP_CRC_CLOCK_REQUEST_ENABLE,
		U300_TIMER_APP_VBASE + U300_TIMER_APP_CRC);
	writel(U300_TIMER_APP_ROST_TIMER_RESET,
		U300_TIMER_APP_VBASE + U300_TIMER_APP_ROST);
	writel(U300_TIMER_APP_DOST_TIMER_DISABLE,
		U300_TIMER_APP_VBASE + U300_TIMER_APP_DOST);
	writel(U300_TIMER_APP_RDDT_TIMER_RESET,
		U300_TIMER_APP_VBASE + U300_TIMER_APP_RDDT);
	writel(U300_TIMER_APP_DDDT_TIMER_DISABLE,
		U300_TIMER_APP_VBASE + U300_TIMER_APP_DDDT);

	/* Reset the General Purpose timer 1. */
	writel(U300_TIMER_APP_RGPT1_TIMER_RESET,
		U300_TIMER_APP_VBASE + U300_TIMER_APP_RGPT1);

	/* Set up the IRQ handler */
	setup_irq(IRQ_U300_TIMER_APP_GP1, &u300_timer_irq);

	/* Reset the General Purpose timer 2 */
	writel(U300_TIMER_APP_RGPT2_TIMER_RESET,
		U300_TIMER_APP_VBASE + U300_TIMER_APP_RGPT2);
	/* Set this timer to run around forever */
	writel(0xFFFFFFFFU, U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT2TC);
	/* Set continuous mode so it wraps around */
	writel(U300_TIMER_APP_SGPT2M_MODE_CONTINUOUS,
	       U300_TIMER_APP_VBASE + U300_TIMER_APP_SGPT2M);
	/* Disable timer interrupts */
	writel(U300_TIMER_APP_GPT2IE_IRQ_DISABLE,
		U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT2IE);
	/* Then enable the GP2 timer to use as a free running us counter */
	writel(U300_TIMER_APP_EGPT2_TIMER_ENABLE,
		U300_TIMER_APP_VBASE + U300_TIMER_APP_EGPT2);

	if (clocksource_register_hz(&clocksource_u300_1mhz, rate))
		printk(KERN_ERR "timer: failed to initialize clock "
		       "source %s\n", clocksource_u300_1mhz.name);

	clockevents_calc_mult_shift(&clockevent_u300_1mhz,
				    rate, APPTIMER_MIN_RANGE);
	/* 32bit counter, so 32bits delta is max */
	clockevent_u300_1mhz.max_delta_ns =
		clockevent_delta2ns(0xffffffff, &clockevent_u300_1mhz);
	/* This timer is slow enough to set for 1 cycle == 1 MHz */
	clockevent_u300_1mhz.min_delta_ns =
		clockevent_delta2ns(1, &clockevent_u300_1mhz);
	clockevent_u300_1mhz.cpumask = cpumask_of(0);
	clockevents_register_device(&clockevent_u300_1mhz);
	/*
	 * TODO: init and register the rest of the timers too, they can be
	 * used by hrtimers!
	 */
}

/*
 * Very simple system timer that only register the clock event and
 * clock source.
 */
struct sys_timer u300_timer = {
	.init		= u300_timer_init,
};