aboutsummaryrefslogtreecommitdiffstats
path: root/arch/i386/kernel/time_hpet.c
blob: a529f0cdce17018dcc6849340954e84731006598 (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
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
/*
 *  linux/arch/i386/kernel/time_hpet.c
 *  This code largely copied from arch/x86_64/kernel/time.c
 *  See that file for credits.
 *
 *  2003-06-30    Venkatesh Pallipadi - Additional changes for HPET support
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/smp.h>

#include <asm/timer.h>
#include <asm/fixmap.h>
#include <asm/apic.h>

#include <linux/timex.h>
#include <linux/config.h>

#include <asm/hpet.h>
#include <linux/hpet.h>

static unsigned long hpet_period;	/* fsecs / HPET clock */
unsigned long hpet_tick;		/* hpet clks count per tick */
unsigned long hpet_address;		/* hpet memory map physical address */
int hpet_use_timer;

static int use_hpet; 		/* can be used for runtime check of hpet */
static int boot_hpet_disable; 	/* boottime override for HPET timer */
static void __iomem * hpet_virt_address;	/* hpet kernel virtual address */

#define FSEC_TO_USEC (1000000000UL)

int hpet_readl(unsigned long a)
{
	return readl(hpet_virt_address + a);
}

static void hpet_writel(unsigned long d, unsigned long a)
{
	writel(d, hpet_virt_address + a);
}

#ifdef CONFIG_X86_LOCAL_APIC
/*
 * HPET counters dont wrap around on every tick. They just change the
 * comparator value and continue. Next tick can be caught by checking
 * for a change in the comparator value. Used in apic.c.
 */
static void __devinit wait_hpet_tick(void)
{
	unsigned int start_cmp_val, end_cmp_val;

	start_cmp_val = hpet_readl(HPET_T0_CMP);
	do {
		end_cmp_val = hpet_readl(HPET_T0_CMP);
	} while (start_cmp_val == end_cmp_val);
}
#endif

static int hpet_timer_stop_set_go(unsigned long tick)
{
	unsigned int cfg;

	/*
	 * Stop the timers and reset the main counter.
	 */
	cfg = hpet_readl(HPET_CFG);
	cfg &= ~HPET_CFG_ENABLE;
	hpet_writel(cfg, HPET_CFG);
	hpet_writel(0, HPET_COUNTER);
	hpet_writel(0, HPET_COUNTER + 4);

	if (hpet_use_timer) {
		/*
		 * Set up timer 0, as periodic with first interrupt to happen at
		 * hpet_tick, and period also hpet_tick.
		 */
		cfg = hpet_readl(HPET_T0_CFG);
		cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC |
		       HPET_TN_SETVAL | HPET_TN_32BIT;
		hpet_writel(cfg, HPET_T0_CFG);

		/*
		 * The first write after writing TN_SETVAL to the config register sets
		 * the counter value, the second write sets the threshold.
		 */
		hpet_writel(tick, HPET_T0_CMP);
		hpet_writel(tick, HPET_T0_CMP);
	}
	/*
 	 * Go!
 	 */
	cfg = hpet_readl(HPET_CFG);
	if (hpet_use_timer)
		cfg |= HPET_CFG_LEGACY;
	cfg |= HPET_CFG_ENABLE;
	hpet_writel(cfg, HPET_CFG);

	return 0;
}

/*
 * Check whether HPET was found by ACPI boot parse. If yes setup HPET
 * counter 0 for kernel base timer.
 */
int __init hpet_enable(void)
{
	unsigned int id;
	unsigned long tick_fsec_low, tick_fsec_high; /* tick in femto sec */
	unsigned long hpet_tick_rem;

	if (boot_hpet_disable)
		return -1;

	if (!hpet_address) {
		return -1;
	}
	hpet_virt_address = ioremap_nocache(hpet_address, HPET_MMAP_SIZE);
	/*
	 * Read the period, compute tick and quotient.
	 */
	id = hpet_readl(HPET_ID);

	/*
	 * We are checking for value '1' or more in number field if
	 * CONFIG_HPET_EMULATE_RTC is set because we will need an
	 * additional timer for RTC emulation.
	 * However, we can do with one timer otherwise using the
	 * the single HPET timer for system time.
	 */
#ifdef CONFIG_HPET_EMULATE_RTC
	if (!(id & HPET_ID_NUMBER))
		return -1;
#endif


	hpet_period = hpet_readl(HPET_PERIOD);
	if ((hpet_period < HPET_MIN_PERIOD) || (hpet_period > HPET_MAX_PERIOD))
		return -1;

	/*
	 * 64 bit math
	 * First changing tick into fsec
	 * Then 64 bit div to find number of hpet clk per tick
	 */
	ASM_MUL64_REG(tick_fsec_low, tick_fsec_high,
			KERNEL_TICK_USEC, FSEC_TO_USEC);
	ASM_DIV64_REG(hpet_tick, hpet_tick_rem,
			hpet_period, tick_fsec_low, tick_fsec_high);

	if (hpet_tick_rem > (hpet_period >> 1))
		hpet_tick++; /* rounding the result */

	hpet_use_timer = id & HPET_ID_LEGSUP;

	if (hpet_timer_stop_set_go(hpet_tick))
		return -1;

	use_hpet = 1;

#ifdef	CONFIG_HPET
	{
		struct hpet_data	hd;
		unsigned int 		ntimer;

		memset(&hd, 0, sizeof (hd));

		ntimer = hpet_readl(HPET_ID);
		ntimer = (ntimer & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT;
		ntimer++;

		/*
		 * Register with driver.
		 * Timer0 and Timer1 is used by platform.
		 */
		hd.hd_phys_address = hpet_address;
		hd.hd_address = hpet_virt_address;
		hd.hd_nirqs = ntimer;
		hd.hd_flags = HPET_DATA_PLATFORM;
		hpet_reserve_timer(&hd, 0);
#ifdef	CONFIG_HPET_EMULATE_RTC
		hpet_reserve_timer(&hd, 1);
#endif
		hd.hd_irq[0] = HPET_LEGACY_8254;
		hd.hd_irq[1] = HPET_LEGACY_RTC;
		if (ntimer > 2) {
			struct hpet __iomem	*hpet;
			struct hpet_timer __iomem *timer;
			int			i;

			hpet = hpet_virt_address;

			for (i = 2, timer = &hpet->hpet_timers[2]; i < ntimer;
				timer++, i++)
				hd.hd_irq[i] = (timer->hpet_config &
					Tn_INT_ROUTE_CNF_MASK) >>
					Tn_INT_ROUTE_CNF_SHIFT;

		}

		hpet_alloc(&hd);
	}
#endif

#ifdef CONFIG_X86_LOCAL_APIC
	if (hpet_use_timer)
		wait_timer_tick = wait_hpet_tick;
#endif
	return 0;
}

int hpet_reenable(void)
{
	return hpet_timer_stop_set_go(hpet_tick);
}

int is_hpet_enabled(void)
{
	return use_hpet;
}

int is_hpet_capable(void)
{
	if (!boot_hpet_disable && hpet_address)
		return 1;
	return 0;
}

static int __init hpet_setup(char* str)
{
	if (str) {
		if (!strncmp("disable", str, 7))
			boot_hpet_disable = 1;
	}
	return 1;
}

__setup("hpet=", hpet_setup);

#ifdef CONFIG_HPET_EMULATE_RTC
/* HPET in LegacyReplacement Mode eats up RTC interrupt line. When, HPET
 * is enabled, we support RTC interrupt functionality in software.
 * RTC has 3 kinds of interrupts:
 * 1) Update Interrupt - generate an interrupt, every sec, when RTC clock
 *    is updated
 * 2) Alarm Interrupt - generate an interrupt at a specific time of day
 * 3) Periodic Interrupt - generate periodic interrupt, with frequencies
 *    2Hz-8192Hz (2Hz-64Hz for non-root user) (all freqs in powers of 2)
 * (1) and (2) above are implemented using polling at a frequency of
 * 64 Hz. The exact frequency is a tradeoff between accuracy and interrupt
 * overhead. (DEFAULT_RTC_INT_FREQ)
 * For (3), we use interrupts at 64Hz or user specified periodic
 * frequency, whichever is higher.
 */
#include <linux/mc146818rtc.h>
#include <linux/rtc.h>

#define DEFAULT_RTC_INT_FREQ 	64
#define RTC_NUM_INTS 		1

static unsigned long UIE_on;
static unsigned long prev_update_sec;

static unsigned long AIE_on;
static struct rtc_time alarm_time;

static unsigned long PIE_on;
static unsigned long PIE_freq = DEFAULT_RTC_INT_FREQ;
static unsigned long PIE_count;

static unsigned long hpet_rtc_int_freq; /* RTC interrupt frequency */
static unsigned int hpet_t1_cmp; /* cached comparator register */

/*
 * Timer 1 for RTC, we do not use periodic interrupt feature,
 * even if HPET supports periodic interrupts on Timer 1.
 * The reason being, to set up a periodic interrupt in HPET, we need to
 * stop the main counter. And if we do that everytime someone diables/enables
 * RTC, we will have adverse effect on main kernel timer running on Timer 0.
 * So, for the time being, simulate the periodic interrupt in software.
 *
 * hpet_rtc_timer_init() is called for the first time and during subsequent
 * interuppts reinit happens through hpet_rtc_timer_reinit().
 */
int hpet_rtc_timer_init(void)
{
	unsigned int cfg, cnt;
	unsigned long flags;

	if (!is_hpet_enabled())
		return 0;
	/*
	 * Set the counter 1 and enable the interrupts.
	 */
	if (PIE_on && (PIE_freq > DEFAULT_RTC_INT_FREQ))
		hpet_rtc_int_freq = PIE_freq;
	else
		hpet_rtc_int_freq = DEFAULT_RTC_INT_FREQ;

	local_irq_save(flags);
	cnt = hpet_readl(HPET_COUNTER);
	cnt += ((hpet_tick*HZ)/hpet_rtc_int_freq);
	hpet_writel(cnt, HPET_T1_CMP);
	hpet_t1_cmp = cnt;
	local_irq_restore(flags);

	cfg = hpet_readl(HPET_T1_CFG);
	cfg &= ~HPET_TN_PERIODIC;
	cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
	hpet_writel(cfg, HPET_T1_CFG);

	return 1;
}

static void hpet_rtc_timer_reinit(void)
{
	unsigned int cfg, cnt;

	if (unlikely(!(PIE_on | AIE_on | UIE_on))) {
		cfg = hpet_readl(HPET_T1_CFG);
		cfg &= ~HPET_TN_ENABLE;
		hpet_writel(cfg, HPET_T1_CFG);
		return;
	}

	if (PIE_on && (PIE_freq > DEFAULT_RTC_INT_FREQ))
		hpet_rtc_int_freq = PIE_freq;
	else
		hpet_rtc_int_freq = DEFAULT_RTC_INT_FREQ;

	/* It is more accurate to use the comparator value than current count.*/
	cnt = hpet_t1_cmp;
	cnt += hpet_tick*HZ/hpet_rtc_int_freq;
	hpet_writel(cnt, HPET_T1_CMP);
	hpet_t1_cmp = cnt;
}

/*
 * The functions below are called from rtc driver.
 * Return 0 if HPET is not being used.
 * Otherwise do the necessary changes and return 1.
 */
int hpet_mask_rtc_irq_bit(unsigned long bit_mask)
{
	if (!is_hpet_enabled())
		return 0;

	if (bit_mask & RTC_UIE)
		UIE_on = 0;
	if (bit_mask & RTC_PIE)
		PIE_on = 0;
	if (bit_mask & RTC_AIE)
		AIE_on = 0;

	return 1;
}

int hpet_set_rtc_irq_bit(unsigned long bit_mask)
{
	int timer_init_reqd = 0;

	if (!is_hpet_enabled())
		return 0;

	if (!(PIE_on | AIE_on | UIE_on))
		timer_init_reqd = 1;

	if (bit_mask & RTC_UIE) {
		UIE_on = 1;
	}
	if (bit_mask & RTC_PIE) {
		PIE_on = 1;
		PIE_count = 0;
	}
	if (bit_mask & RTC_AIE) {
		AIE_on = 1;
	}

	if (timer_init_reqd)
		hpet_rtc_timer_init();

	return 1;
}

int hpet_set_alarm_time(unsigned char hrs, unsigned char min, unsigned char sec)
{
	if (!is_hpet_enabled())
		return 0;

	alarm_time.tm_hour = hrs;
	alarm_time.tm_min = min;
	alarm_time.tm_sec = sec;

	return 1;
}

int hpet_set_periodic_freq(unsigned long freq)
{
	if (!is_hpet_enabled())
		return 0;

	PIE_freq = freq;
	PIE_count = 0;

	return 1;
}

int hpet_rtc_dropped_irq(void)
{
	if (!is_hpet_enabled())
		return 0;

	return 1;
}

irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
	struct rtc_time curr_time;
	unsigned long rtc_int_flag = 0;
	int call_rtc_interrupt = 0;

	hpet_rtc_timer_reinit();

	if (UIE_on | AIE_on) {
		rtc_get_rtc_time(&curr_time);
	}
	if (UIE_on) {
		if (curr_time.tm_sec != prev_update_sec) {
			/* Set update int info, call real rtc int routine */
			call_rtc_interrupt = 1;
			rtc_int_flag = RTC_UF;
			prev_update_sec = curr_time.tm_sec;
		}
	}
	if (PIE_on) {
		PIE_count++;
		if (PIE_count >= hpet_rtc_int_freq/PIE_freq) {
			/* Set periodic int info, call real rtc int routine */
			call_rtc_interrupt = 1;
			rtc_int_flag |= RTC_PF;
			PIE_count = 0;
		}
	}
	if (AIE_on) {
		if ((curr_time.tm_sec == alarm_time.tm_sec) &&
		    (curr_time.tm_min == alarm_time.tm_min) &&
		    (curr_time.tm_hour == alarm_time.tm_hour)) {
			/* Set alarm int info, call real rtc int routine */
			call_rtc_interrupt = 1;
			rtc_int_flag |= RTC_AF;
		}
	}
	if (call_rtc_interrupt) {
		rtc_int_flag |= (RTC_IRQF | (RTC_NUM_INTS << 8));
		rtc_interrupt(rtc_int_flag, dev_id, regs);
	}
	return IRQ_HANDLED;
}
#endif