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
!= (int)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
;
63 time_t t
= read_rtc(pp_rtcname
, &sys_tv
, utc
);
65 #if ENABLE_LOCALE_SUPPORT
66 /* Standard hwclock uses locale-specific output format */
68 struct tm
*ptm
= localtime(&t
);
69 strftime(cp
, sizeof(cp
), "%c", ptm
);
72 strchrnul(cp
, '\n')[0] = '\0';
75 #if !SHOW_HWCLOCK_DIFF
76 printf("%s 0.000000 seconds\n", cp
);
79 long diff
= sys_tv
.tv_sec
- t
;
80 if (diff
< 0 /*&& tv.tv_usec != 0*/) {
81 /* Why we need diff++? */
82 /* diff >= 0 is ok: | diff < 0, can't just use tv.tv_usec: */
83 /* 45.520820 | 43.520820 */
84 /* - 44.000000 | - 45.000000 */
85 /* = 1.520820 | = -1.479180, not -2.520820! */
87 /* Should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */
88 sys_tv
.tv_usec
= 999999 - sys_tv
.tv_usec
;
90 printf("%s %ld.%06lu seconds\n", cp
, diff
, (unsigned long)sys_tv
.tv_usec
);
95 static void to_sys_clock(const char **pp_rtcname
, int utc
)
100 tz
.tz_minuteswest
= timezone
/60 - 60*daylight
;
103 tv
.tv_sec
= read_rtc(pp_rtcname
, NULL
, utc
);
105 if (settimeofday(&tv
, &tz
))
106 bb_perror_msg_and_die("settimeofday");
109 static void from_sys_clock(const char **pp_rtcname
, int utc
)
116 rtc
= rtc_xopen(pp_rtcname
, O_WRONLY
);
117 gettimeofday(&tv
, NULL
);
118 /* Prepare tm_time */
119 if (sizeof(time_t) == sizeof(tv
.tv_sec
)) {
121 gmtime_r((time_t*)&tv
.tv_sec
, &tm_time
);
123 localtime_r((time_t*)&tv
.tv_sec
, &tm_time
);
125 time_t t
= tv
.tv_sec
;
127 gmtime_r(&t
, &tm_time
);
129 localtime_r(&t
, &tm_time
);
132 /* Bloated code which tries to set hw clock with better precision.
133 * On x86, even though code does set hw clock within <1ms of exact
134 * whole seconds, apparently hw clock (at least on some machines)
135 * doesn't reset internal fractional seconds to 0,
136 * making all this a pointless excercise.
138 /* If we see that we are N usec away from whole second,
139 * we'll sleep for N-ADJ usecs. ADJ corrects for the fact
140 * that CPU is not infinitely fast.
141 * On infinitely fast CPU, next wakeup would be
142 * on (exactly_next_whole_second - ADJ). On real CPUs,
143 * this difference between current time and whole second
144 * is less than ADJ (assuming system isn't heavily loaded).
146 /* Small value of 256us gives very precise sync for 2+ GHz CPUs.
147 * Slower CPUs will fail to sync and will go to bigger
148 * ADJ values. qemu-emulated armv4tl with ~100 MHz
149 * performance ends up using ADJ ~= 4*1024 and it takes
150 * 2+ secs (2 tries with successively larger ADJ)
151 * to sync. Even straced one on the same qemu (very slow)
152 * takes only 4 tries.
154 #define TWEAK_USEC 256
155 unsigned adj
= TWEAK_USEC
;
158 int rtc
= rtc_xopen(pp_rtcname
, O_WRONLY
);
160 /* Try to catch the moment when whole second is close */
165 gettimeofday(&tv
, NULL
);
168 rem_usec
= 1000000 - tv
.tv_usec
;
169 if (rem_usec
< adj
) {
175 /* Prepare tm_time from t */
177 gmtime_r(&t
, &tm_time
); /* may read /etc/xxx (it takes time) */
179 localtime_r(&t
, &tm_time
); /* same */
181 if (adj
>= 32*1024) {
182 break; /* 32 ms diff and still no luck?? give up trying to sync */
185 /* gmtime/localtime took some time, re-get cur time */
186 gettimeofday(&tv
, NULL
);
188 if (tv
.tv_sec
< t
/* we are still in old second */
189 || (tv
.tv_sec
== t
&& tv
.tv_usec
< adj
) /* not too far into next second */
191 break; /* good, we are in sync! */
194 rem_usec
= 1000000 - tv
.tv_usec
;
195 if (rem_usec
< adj
) {
197 goto small_rem
; /* already close to next sec, don't sleep */
200 /* Try to sync up by sleeping */
201 usleep(rem_usec
- adj
);
203 /* Jump to 1ms diff, then increase fast (x2): EVERY loop
204 * takes ~1 sec, people won't like slowly converging code here!
206 //bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec);
209 /* ... and if last "overshoot" does not look insanely big,
210 * just use it as adj increment. This makes convergence faster.
212 if (tv
.tv_usec
< adj
* 8) {
218 /* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync.
219 * Look for a value which makes tv_usec close to 999999 or 0.
220 * For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200
222 //bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec);
225 tm_time
.tm_isdst
= 0;
226 xioctl(rtc
, RTC_SET_TIME
, &tm_time
);
228 if (ENABLE_FEATURE_CLEAN_UP
)
233 * At system boot, kernel may set system time from RTC,
234 * but it knows nothing about timezones. If RTC is in local time,
235 * then system time is wrong - it is offset by timezone.
236 * This option corrects system time if RTC is in local time,
237 * and (always) sets in-kernel timezone.
239 * This is an alternate option to --hctosys that does not read the
242 static void set_system_clock_timezone(int utc
)
248 gettimeofday(&tv
, NULL
);
249 broken
= localtime(&tv
.tv_sec
);
250 tz
.tz_minuteswest
= timezone
/ 60;
251 if (broken
->tm_isdst
)
252 tz
.tz_minuteswest
-= 60;
254 gettimeofday(&tv
, NULL
);
256 tv
.tv_sec
+= tz
.tz_minuteswest
* 60;
257 if (settimeofday(&tv
, &tz
))
258 bb_perror_msg_and_die("settimeofday");
261 //usage:#define hwclock_trivial_usage
262 //usage: IF_FEATURE_HWCLOCK_LONG_OPTIONS(
263 //usage: "[-r|--show] [-s|--hctosys] [-w|--systohc] [-t|--systz]"
264 //usage: " [-l|--localtime] [-u|--utc]"
265 //usage: " [-f|--rtc FILE]"
267 //usage: IF_NOT_FEATURE_HWCLOCK_LONG_OPTIONS(
268 //usage: "[-r] [-s] [-w] [-t] [-l] [-u] [-f FILE]"
270 //usage:#define hwclock_full_usage "\n\n"
271 //usage: "Query and set hardware clock (RTC)\n"
272 //usage: "\n -r Show hardware clock time"
273 //usage: "\n -s Set system time from hardware clock"
274 //usage: "\n -w Set hardware clock from system time"
275 //usage: "\n -t Set in-kernel timezone, correct system time"
276 //usage: "\n if hardware clock is in local time"
277 //usage: "\n -u Assume hardware clock is kept in UTC"
278 //usage: "\n -l Assume hardware clock is kept in local time"
279 //usage: "\n -f FILE Use specified device (e.g. /dev/rtc2)"
281 #define HWCLOCK_OPT_LOCALTIME 0x01
282 #define HWCLOCK_OPT_UTC 0x02
283 #define HWCLOCK_OPT_SHOW 0x04
284 #define HWCLOCK_OPT_HCTOSYS 0x08
285 #define HWCLOCK_OPT_SYSTOHC 0x10
286 #define HWCLOCK_OPT_SYSTZ 0x20
287 #define HWCLOCK_OPT_RTCFILE 0x40
289 int hwclock_main(int argc
, char **argv
) MAIN_EXTERNALLY_VISIBLE
;
290 int hwclock_main(int argc UNUSED_PARAM
, char **argv
)
292 const char *rtcname
= NULL
;
296 #if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS
297 static const char hwclock_longopts
[] ALIGN1
=
298 "localtime\0" No_argument
"l" /* short opt is non-standard */
299 "utc\0" No_argument
"u"
300 "show\0" No_argument
"r"
301 "hctosys\0" No_argument
"s"
302 "systohc\0" No_argument
"w"
303 "systz\0" No_argument
"t" /* short opt is non-standard */
304 "rtc\0" Required_argument
"f"
306 applet_long_options
= hwclock_longopts
;
308 opt_complementary
= "r--wst:w--rst:s--wrt:t--rsw:l--u:u--l";
309 opt
= getopt32(argv
, "lurswtf:", &rtcname
);
311 /* If -u or -l wasn't given check if we are using utc */
312 if (opt
& (HWCLOCK_OPT_UTC
| HWCLOCK_OPT_LOCALTIME
))
313 utc
= (opt
& HWCLOCK_OPT_UTC
);
315 utc
= rtc_adjtime_is_utc();
317 if (opt
& HWCLOCK_OPT_HCTOSYS
)
318 to_sys_clock(&rtcname
, utc
);
319 else if (opt
& HWCLOCK_OPT_SYSTOHC
)
320 from_sys_clock(&rtcname
, utc
);
321 else if (opt
& HWCLOCK_OPT_SYSTZ
)
322 set_system_clock_timezone(utc
);
324 /* default HWCLOCK_OPT_SHOW */
325 show_clock(&rtcname
, utc
);