1 /* vi: set sw=4 ts=4: */
3 * Mini hwclock implementation for busybox
5 * Copyright (C) 2002 Robert Griebl <griebl@gmx.de>
7 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
11 /* After libbb.h, since it needs sys/types.h on some systems */
12 #include <sys/utsname.h>
15 /* diff code is disabled: it's not sys/hw clock diff, it's some useless
16 * "time between hwclock was started and we saw CMOS tick" quantity.
17 * It's useless since hwclock is started at a random moment,
18 * thus the quantity is also random, useless. Showing 0.000000 does not
19 * deprive us from any useful info.
21 * SHOW_HWCLOCK_DIFF code in this file shows the difference between system
22 * and hw clock. It is useful, but not compatible with standard hwclock.
25 #define SHOW_HWCLOCK_DIFF 0
28 #if !SHOW_HWCLOCK_DIFF
29 # define read_rtc(pp_rtcname, sys_tv, utc) read_rtc(pp_rtcname, utc)
31 static time_t read_rtc(const char **pp_rtcname, struct timeval *sys_tv, int utc)
36 fd = rtc_xopen(pp_rtcname, O_RDONLY);
38 rtc_read_tm(&tm_time, fd);
42 int before = tm_time.tm_sec;
44 rtc_read_tm(&tm_time, fd);
45 gettimeofday(sys_tv, NULL);
46 if (before != tm_time.tm_sec)
52 if (ENABLE_FEATURE_CLEAN_UP)
55 return rtc_tm2time(&tm_time, utc);
58 static void show_clock(const char **pp_rtcname, int utc)
61 struct timeval sys_tv;
66 t = read_rtc(pp_rtcname, &sys_tv, utc);
68 strchrnul(cp, '\n')[0] = '\0';
69 #if !SHOW_HWCLOCK_DIFF
70 printf("%s 0.000000 seconds\n", cp);
73 long diff = sys_tv.tv_sec - t;
74 if (diff < 0 /*&& tv.tv_usec != 0*/) {
76 /* diff >= 0 is ok: diff < 0, can't just use tv.tv_usec: */
77 /* 45.520820 43.520820 */
78 /* - 44.000000 - 45.000000 */
79 /* = 1.520820 = -1.479180, not -2.520820! */
81 /* should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */
82 sys_tv.tv_usec = 999999 - sys_tv.tv_usec;
84 printf("%s %ld.%06lu seconds\n", cp, diff, (unsigned long)sys_tv.tv_usec);
89 static void to_sys_clock(const char **pp_rtcname, int utc)
94 tz.tz_minuteswest = timezone/60 - 60*daylight;
97 tv.tv_sec = read_rtc(pp_rtcname, NULL, utc);
99 if (settimeofday(&tv, &tz))
100 bb_perror_msg_and_die("settimeofday");
103 static void from_sys_clock(const char **pp_rtcname, int utc)
110 rtc = rtc_xopen(pp_rtcname, O_WRONLY);
111 gettimeofday(&tv, NULL);
112 /* Prepare tm_time */
113 if (sizeof(time_t) == sizeof(tv.tv_sec)) {
115 gmtime_r((time_t*)&tv.tv_sec, &tm_time);
117 localtime_r((time_t*)&tv.tv_sec, &tm_time);
119 time_t t = tv.tv_sec;
121 gmtime_r(&t, &tm_time);
123 localtime_r(&t, &tm_time);
126 /* Bloated code which tries to set hw clock with better precision.
127 * On x86, even though code does set hw clock within <1ms of exact
128 * whole seconds, apparently hw clock (at least on some machines)
129 * doesn't reset internal fractional seconds to 0,
130 * making all this a pointless excercise.
132 /* If we see that we are N usec away from whole second,
133 * we'll sleep for N-ADJ usecs. ADJ corrects for the fact
134 * that CPU is not infinitely fast.
135 * On infinitely fast CPU, next wakeup would be
136 * on (exactly_next_whole_second - ADJ). On real CPUs,
137 * this difference between current time and whole second
138 * is less than ADJ (assuming system isn't heavily loaded).
140 /* Small value of 256us gives very precise sync for 2+ GHz CPUs.
141 * Slower CPUs will fail to sync and will go to bigger
142 * ADJ values. qemu-emulated armv4tl with ~100 MHz
143 * performance ends up using ADJ ~= 4*1024 and it takes
144 * 2+ secs (2 tries with successively larger ADJ)
145 * to sync. Even straced one on the same qemu (very slow)
146 * takes only 4 tries.
148 #define TWEAK_USEC 256
149 unsigned adj = TWEAK_USEC;
152 int rtc = rtc_xopen(pp_rtcname, O_WRONLY);
154 /* Try to catch the moment when whole second is close */
159 gettimeofday(&tv, NULL);
162 rem_usec = 1000000 - tv.tv_usec;
163 if (rem_usec < adj) {
169 /* Prepare tm_time from t */
171 gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */
173 localtime_r(&t, &tm_time); /* same */
175 if (adj >= 32*1024) {
176 break; /* 32 ms diff and still no luck?? give up trying to sync */
179 /* gmtime/localtime took some time, re-get cur time */
180 gettimeofday(&tv, NULL);
182 if (tv.tv_sec < t /* we are still in old second */
183 || (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */
185 break; /* good, we are in sync! */
188 rem_usec = 1000000 - tv.tv_usec;
189 if (rem_usec < adj) {
191 goto small_rem; /* already close to next sec, don't sleep */
194 /* Try to sync up by sleeping */
195 usleep(rem_usec - adj);
197 /* Jump to 1ms diff, then increase fast (x2): EVERY loop
198 * takes ~1 sec, people won't like slowly converging code here!
200 //bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec);
203 /* ... and if last "overshoot" does not look insanely big,
204 * just use it as adj increment. This makes convergence faster.
206 if (tv.tv_usec < adj * 8) {
212 /* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync.
213 * Look for a value which makes tv_usec close to 999999 or 0.
214 * For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200
216 //bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec);
219 tm_time.tm_isdst = 0;
220 xioctl(rtc, RTC_SET_TIME, &tm_time);
222 if (ENABLE_FEATURE_CLEAN_UP)
227 * At system boot, kernel may set system time from RTC,
228 * but it knows nothing about timezones. If RTC is in local time,
229 * then system time is wrong - it is offset by timezone.
230 * This option corrects system time if RTC is in local time,
231 * and (always) sets in-kernel timezone.
233 * This is an alternate option to --hctosys that does not read the
236 static void set_system_clock_timezone(int utc)
242 gettimeofday(&tv, NULL);
243 broken = localtime(&tv.tv_sec);
244 tz.tz_minuteswest = timezone / 60;
245 if (broken->tm_isdst)
246 tz.tz_minuteswest -= 60;
248 gettimeofday(&tv, NULL);
250 tv.tv_sec += tz.tz_minuteswest * 60;
251 if (settimeofday(&tv, &tz))
252 bb_perror_msg_and_die("settimeofday");
255 //usage:#define hwclock_trivial_usage
256 //usage: IF_FEATURE_HWCLOCK_LONG_OPTIONS(
257 //usage: "[-r|--show] [-s|--hctosys] [-w|--systohc] [-t|--systz]"
258 //usage: " [-l|--localtime] [-u|--utc]"
259 //usage: " [-f|--rtc FILE]"
261 //usage: IF_NOT_FEATURE_HWCLOCK_LONG_OPTIONS(
262 //usage: "[-r] [-s] [-w] [-t] [-l] [-u] [-f FILE]"
264 //usage:#define hwclock_full_usage "\n\n"
265 //usage: "Query and set hardware clock (RTC)\n"
266 //usage: "\nOptions:"
267 //usage: "\n -r Show hardware clock time"
268 //usage: "\n -s Set system time from hardware clock"
269 //usage: "\n -w Set hardware clock from system time"
270 //usage: "\n -t Set in-kernel timezone, correct system time"
271 //usage: "\n if hardware clock is in local time"
272 //usage: "\n -u Hardware clock is in UTC"
273 //usage: "\n -l Hardware clock is in local time"
274 //usage: "\n -f FILE Use specified device (e.g. /dev/rtc2)"
276 #define HWCLOCK_OPT_LOCALTIME 0x01
277 #define HWCLOCK_OPT_UTC 0x02
278 #define HWCLOCK_OPT_SHOW 0x04
279 #define HWCLOCK_OPT_HCTOSYS 0x08
280 #define HWCLOCK_OPT_SYSTOHC 0x10
281 #define HWCLOCK_OPT_SYSTZ 0x20
282 #define HWCLOCK_OPT_RTCFILE 0x40
284 int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
285 int hwclock_main(int argc UNUSED_PARAM, char **argv)
287 const char *rtcname = NULL;
291 #if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS
292 static const char hwclock_longopts[] ALIGN1 =
293 "localtime\0" No_argument "l" /* short opt is non-standard */
294 "utc\0" No_argument "u"
295 "show\0" No_argument "r"
296 "hctosys\0" No_argument "s"
297 "systohc\0" No_argument "w"
298 "systz\0" No_argument "t" /* short opt is non-standard */
299 "rtc\0" Required_argument "f"
301 applet_long_options = hwclock_longopts;
303 opt_complementary = "r--wst:w--rst:s--wrt:t--rsw:l--u:u--l";
304 opt = getopt32(argv, "lurswtf:", &rtcname);
306 /* If -u or -l wasn't given check if we are using utc */
307 if (opt & (HWCLOCK_OPT_UTC | HWCLOCK_OPT_LOCALTIME))
308 utc = (opt & HWCLOCK_OPT_UTC);
310 utc = rtc_adjtime_is_utc();
312 if (opt & HWCLOCK_OPT_HCTOSYS)
313 to_sys_clock(&rtcname, utc);
314 else if (opt & HWCLOCK_OPT_SYSTOHC)
315 from_sys_clock(&rtcname, utc);
316 else if (opt & HWCLOCK_OPT_SYSTZ)
317 set_system_clock_timezone(utc);
319 /* default HWCLOCK_OPT_SHOW */
320 show_clock(&rtcname, utc);