xref: /openbmc/linux/arch/um/os-Linux/time.c (revision 4800cd83)
1 /*
2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
3  * Licensed under the GPL
4  */
5 
6 #include <stddef.h>
7 #include <errno.h>
8 #include <signal.h>
9 #include <time.h>
10 #include <sys/time.h>
11 #include "kern_constants.h"
12 #include "kern_util.h"
13 #include "os.h"
14 #include "process.h"
15 #include "user.h"
16 
17 int set_interval(void)
18 {
19 	int usec = UM_USEC_PER_SEC / UM_HZ;
20 	struct itimerval interval = ((struct itimerval) { { 0, usec },
21 							  { 0, usec } });
22 
23 	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
24 		return -errno;
25 
26 	return 0;
27 }
28 
29 int timer_one_shot(int ticks)
30 {
31 	unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
32 	unsigned long sec = usec / UM_USEC_PER_SEC;
33 	struct itimerval interval;
34 
35 	usec %= UM_USEC_PER_SEC;
36 	interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
37 
38 	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
39 		return -errno;
40 
41 	return 0;
42 }
43 
44 /**
45  * timeval_to_ns - Convert timeval to nanoseconds
46  * @ts:		pointer to the timeval variable to be converted
47  *
48  * Returns the scalar nanosecond representation of the timeval
49  * parameter.
50  *
51  * Ripped from linux/time.h because it's a kernel header, and thus
52  * unusable from here.
53  */
54 static inline long long timeval_to_ns(const struct timeval *tv)
55 {
56 	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
57 		tv->tv_usec * UM_NSEC_PER_USEC;
58 }
59 
60 long long disable_timer(void)
61 {
62 	struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
63 	long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
64 
65 	if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
66 		printk(UM_KERN_ERR "disable_timer - setitimer failed, "
67 		       "errno = %d\n", errno);
68 
69 	remain = timeval_to_ns(&time.it_value);
70 	if (remain > max)
71 		remain = max;
72 
73 	return remain;
74 }
75 
76 long long os_nsecs(void)
77 {
78 	struct timeval tv;
79 
80 	gettimeofday(&tv, NULL);
81 	return timeval_to_ns(&tv);
82 }
83 
84 #ifdef UML_CONFIG_NO_HZ
85 static int after_sleep_interval(struct timespec *ts)
86 {
87 	return 0;
88 }
89 
90 static void deliver_alarm(void)
91 {
92 	alarm_handler(SIGVTALRM, NULL);
93 }
94 
95 static unsigned long long sleep_time(unsigned long long nsecs)
96 {
97 	return nsecs;
98 }
99 
100 #else
101 unsigned long long last_tick;
102 unsigned long long skew;
103 
104 static void deliver_alarm(void)
105 {
106 	unsigned long long this_tick = os_nsecs();
107 	int one_tick = UM_NSEC_PER_SEC / UM_HZ;
108 
109 	/* Protection against the host's time going backwards */
110 	if ((last_tick != 0) && (this_tick < last_tick))
111 		this_tick = last_tick;
112 
113 	if (last_tick == 0)
114 		last_tick = this_tick - one_tick;
115 
116 	skew += this_tick - last_tick;
117 
118 	while (skew >= one_tick) {
119 		alarm_handler(SIGVTALRM, NULL);
120 		skew -= one_tick;
121 	}
122 
123 	last_tick = this_tick;
124 }
125 
126 static unsigned long long sleep_time(unsigned long long nsecs)
127 {
128 	return nsecs > skew ? nsecs - skew : 0;
129 }
130 
131 static inline long long timespec_to_us(const struct timespec *ts)
132 {
133 	return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
134 		ts->tv_nsec / UM_NSEC_PER_USEC;
135 }
136 
137 static int after_sleep_interval(struct timespec *ts)
138 {
139 	int usec = UM_USEC_PER_SEC / UM_HZ;
140 	long long start_usecs = timespec_to_us(ts);
141 	struct timeval tv;
142 	struct itimerval interval;
143 
144 	/*
145 	 * It seems that rounding can increase the value returned from
146 	 * setitimer to larger than the one passed in.  Over time,
147 	 * this will cause the remaining time to be greater than the
148 	 * tick interval.  If this happens, then just reduce the first
149 	 * tick to the interval value.
150 	 */
151 	if (start_usecs > usec)
152 		start_usecs = usec;
153 
154 	start_usecs -= skew / UM_NSEC_PER_USEC;
155 	if (start_usecs < 0)
156 		start_usecs = 0;
157 
158 	tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
159 				 .tv_usec = start_usecs % UM_USEC_PER_SEC });
160 	interval = ((struct itimerval) { { 0, usec }, tv });
161 
162 	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
163 		return -errno;
164 
165 	return 0;
166 }
167 #endif
168 
169 void idle_sleep(unsigned long long nsecs)
170 {
171 	struct timespec ts;
172 
173 	/*
174 	 * nsecs can come in as zero, in which case, this starts a
175 	 * busy loop.  To prevent this, reset nsecs to the tick
176 	 * interval if it is zero.
177 	 */
178 	if (nsecs == 0)
179 		nsecs = UM_NSEC_PER_SEC / UM_HZ;
180 
181 	nsecs = sleep_time(nsecs);
182 	ts = ((struct timespec) { .tv_sec	= nsecs / UM_NSEC_PER_SEC,
183 				  .tv_nsec	= nsecs % UM_NSEC_PER_SEC });
184 
185 	if (nanosleep(&ts, &ts) == 0)
186 		deliver_alarm();
187 	after_sleep_interval(&ts);
188 }
189