summaryrefslogtreecommitdiff
path: root/arch/blackfin/kernel/time.c
blob: 5bd64e341df39cb53c9f70b29229274a72a416c9 (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
/*
 * File:         arch/blackfin/kernel/time.c
 * Based on:     none - original work
 * Author:
 *
 * Created:
 * Description:  This file contains the bfin-specific time handling details.
 *               Most of the stuff is located in the machine specific files.
 *
 * Modified:
 *               Copyright 2004-2006 Analog Devices Inc.
 *
 * Bugs:         Enter bugs at http://blackfin.uclinux.org/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see the file COPYING, or write
 * to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <linux/module.h>
#include <linux/profile.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/irq.h>

#include <asm/blackfin.h>

/* This is an NTP setting */
#define	TICK_SIZE (tick_nsec / 1000)

static void time_sched_init(irqreturn_t(*timer_routine)
			(int, void *));
static unsigned long gettimeoffset(void);

static struct irqaction bfin_timer_irq = {
	.name = "BFIN Timer Tick",
	.flags = IRQF_DISABLED
};

/*
 * The way that the Blackfin core timer works is:
 *  - CCLK is divided by a programmable 8-bit pre-scaler (TSCALE)
 *  - Every time TSCALE ticks, a 32bit is counted down (TCOUNT)
 *
 * If you take the fastest clock (1ns, or 1GHz to make the math work easier)
 *    10ms is 10,000,000 clock ticks, which fits easy into a 32-bit counter
 *    (32 bit counter is 4,294,967,296ns or 4.2 seconds) so, we don't need
 *    to use TSCALE, and program it to zero (which is pass CCLK through).
 *    If you feel like using it, try to keep HZ * TIMESCALE to some
 *    value that divides easy (like power of 2).
 */

#define TIME_SCALE 1

static void
time_sched_init(irqreturn_t(*timer_routine) (int, void *))
{
	u32 tcount;

	/* power up the timer, but don't enable it just yet */
	bfin_write_TCNTL(1);
	CSYNC();

	/*
	 * the TSCALE prescaler counter.
	 */
	bfin_write_TSCALE((TIME_SCALE - 1));

	tcount = ((get_cclk() / (HZ * TIME_SCALE)) - 1);
	bfin_write_TPERIOD(tcount);
	bfin_write_TCOUNT(tcount);

	/* now enable the timer */
	CSYNC();

	bfin_write_TCNTL(7);

	bfin_timer_irq.handler = (irq_handler_t)timer_routine;
	/* call setup_irq instead of request_irq because request_irq calls
	 * kmalloc which has not been initialized yet
	 */
	setup_irq(IRQ_CORETMR, &bfin_timer_irq);
}

/*
 * Should return useconds since last timer tick
 */
static unsigned long gettimeoffset(void)
{
	unsigned long offset;
	unsigned long clocks_per_jiffy;

	clocks_per_jiffy = bfin_read_TPERIOD();
	offset =
	    (clocks_per_jiffy -
	     bfin_read_TCOUNT()) / (((clocks_per_jiffy + 1) * HZ) /
				    USEC_PER_SEC);

	/* Check if we just wrapped the counters and maybe missed a tick */
	if ((bfin_read_ILAT() & (1 << IRQ_CORETMR))
	    && (offset < (100000 / HZ / 2)))
		offset += (USEC_PER_SEC / HZ);

	return offset;
}

static inline int set_rtc_mmss(unsigned long nowtime)
{
	return 0;
}

/*
 * timer_interrupt() needs to keep up the real-time clock,
 * as well as call the "do_timer()" routine every clocktick
 */
#ifdef CONFIG_CORE_TIMER_IRQ_L1
irqreturn_t timer_interrupt(int irq, void *dummy)__attribute__((l1_text));
#endif

irqreturn_t timer_interrupt(int irq, void *dummy)
{
	/* last time the cmos clock got updated */
	static long last_rtc_update;

	write_seqlock(&xtime_lock);

	do_timer(1);

#ifndef CONFIG_SMP
	update_process_times(user_mode(get_irq_regs()));
#endif
	profile_tick(CPU_PROFILING);

	/*
	 * If we have an externally synchronized Linux clock, then update
	 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
	 * called as close as possible to 500 ms before the new second starts.
	 */

	if (ntp_synced() &&
	    xtime.tv_sec > last_rtc_update + 660 &&
	    (xtime.tv_nsec / NSEC_PER_USEC) >=
	    500000 - ((unsigned)TICK_SIZE) / 2
	    && (xtime.tv_nsec / NSEC_PER_USEC) <=
	    500000 + ((unsigned)TICK_SIZE) / 2) {
		if (set_rtc_mmss(xtime.tv_sec) == 0)
			last_rtc_update = xtime.tv_sec;
		else
			/* Do it again in 60s. */
			last_rtc_update = xtime.tv_sec - 600;
	}
	write_sequnlock(&xtime_lock);
	return IRQ_HANDLED;
}

void __init time_init(void)
{
	time_t secs_since_1970 = (365 * 37 + 9) * 24 * 60 * 60;	/* 1 Jan 2007 */

#ifdef CONFIG_RTC_DRV_BFIN
	/* [#2663] hack to filter junk RTC values that would cause
	 * userspace to have to deal with time values greater than
	 * 2^31 seconds (which uClibc cannot cope with yet)
	 */
	if ((bfin_read_RTC_STAT() & 0xC0000000) == 0xC0000000) {
		printk(KERN_NOTICE "bfin-rtc: invalid date; resetting\n");
		bfin_write_RTC_STAT(0);
	}
#endif

	/* Initialize xtime. From now on, xtime is updated with timer interrupts */
	xtime.tv_sec = secs_since_1970;
	xtime.tv_nsec = 0;

	wall_to_monotonic.tv_sec = -xtime.tv_sec;

	time_sched_init(timer_interrupt);
}

#ifndef CONFIG_GENERIC_TIME
void do_gettimeofday(struct timeval *tv)
{
	unsigned long flags;
	unsigned long seq;
	unsigned long usec, sec;

	do {
		seq = read_seqbegin_irqsave(&xtime_lock, flags);
		usec = gettimeoffset();
		sec = xtime.tv_sec;
		usec += (xtime.tv_nsec / NSEC_PER_USEC);
	}
	while (read_seqretry_irqrestore(&xtime_lock, seq, flags));

	while (usec >= USEC_PER_SEC) {
		usec -= USEC_PER_SEC;
		sec++;
	}

	tv->tv_sec = sec;
	tv->tv_usec = usec;
}
EXPORT_SYMBOL(do_gettimeofday);

int do_settimeofday(struct timespec *tv)
{
	time_t wtm_sec, sec = tv->tv_sec;
	long wtm_nsec, nsec = tv->tv_nsec;

	if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
		return -EINVAL;

	write_seqlock_irq(&xtime_lock);
	/*
	 * This is revolting. We need to set the xtime.tv_usec
	 * correctly. However, the value in this location is
	 * is value at the last tick.
	 * Discover what correction gettimeofday
	 * would have done, and then undo it!
	 */
	nsec -= (gettimeoffset() * NSEC_PER_USEC);

	wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
	wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);

	set_normalized_timespec(&xtime, sec, nsec);
	set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);

	ntp_clear();

	write_sequnlock_irq(&xtime_lock);
	clock_was_set();

	return 0;
}
EXPORT_SYMBOL(do_settimeofday);
#endif /* !CONFIG_GENERIC_TIME */

/*
 * Scheduler clock - returns current time in nanosec units.
 */
unsigned long long sched_clock(void)
{
	return (unsigned long long)jiffies *(NSEC_PER_SEC / HZ);
}