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This change retains "or later" state! No licensing _changes_ here, only form is adjusted (article, space between "GPL" and "v2" and so on). Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
270 lines
7.0 KiB
C
270 lines
7.0 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Mini hwclock implementation for busybox
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*
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* Copyright (C) 2002 Robert Griebl <griebl@gmx.de>
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*
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* Licensed under GPLv2 or later, see file LICENSE in this source tree.
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*/
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#include "libbb.h"
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/* After libbb.h, since it needs sys/types.h on some systems */
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#include <sys/utsname.h>
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#include "rtc_.h"
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/* diff code is disabled: it's not sys/hw clock diff, it's some useless
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* "time between hwclock was started and we saw CMOS tick" quantity.
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* It's useless since hwclock is started at a random moment,
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* thus the quantity is also random, useless. Showing 0.000000 does not
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* deprive us from any useful info.
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*
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* SHOW_HWCLOCK_DIFF code in this file shows the difference between system
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* and hw clock. It is useful, but not compatible with standard hwclock.
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* Thus disabled.
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*/
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#define SHOW_HWCLOCK_DIFF 0
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#if !SHOW_HWCLOCK_DIFF
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# define read_rtc(pp_rtcname, sys_tv, utc) read_rtc(pp_rtcname, utc)
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#endif
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static time_t read_rtc(const char **pp_rtcname, struct timeval *sys_tv, int utc)
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{
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struct tm tm_time;
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int fd;
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fd = rtc_xopen(pp_rtcname, O_RDONLY);
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rtc_read_tm(&tm_time, fd);
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#if SHOW_HWCLOCK_DIFF
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{
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int before = tm_time.tm_sec;
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while (1) {
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rtc_read_tm(&tm_time, fd);
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gettimeofday(sys_tv, NULL);
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if (before != tm_time.tm_sec)
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break;
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}
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}
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#endif
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if (ENABLE_FEATURE_CLEAN_UP)
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close(fd);
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return rtc_tm2time(&tm_time, utc);
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}
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static void show_clock(const char **pp_rtcname, int utc)
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{
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#if SHOW_HWCLOCK_DIFF
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struct timeval sys_tv;
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#endif
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time_t t;
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char *cp;
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t = read_rtc(pp_rtcname, &sys_tv, utc);
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cp = ctime(&t);
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strchrnul(cp, '\n')[0] = '\0';
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#if !SHOW_HWCLOCK_DIFF
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printf("%s 0.000000 seconds\n", cp);
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#else
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{
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long diff = sys_tv.tv_sec - t;
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if (diff < 0 /*&& tv.tv_usec != 0*/) {
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/* Why? */
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/* diff >= 0 is ok: diff < 0, can't just use tv.tv_usec: */
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/* 45.520820 43.520820 */
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/* - 44.000000 - 45.000000 */
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/* = 1.520820 = -1.479180, not -2.520820! */
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diff++;
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/* should be 1000000 - tv.tv_usec, but then we must check tv.tv_usec != 0 */
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sys_tv.tv_usec = 999999 - sys_tv.tv_usec;
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}
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printf("%s %ld.%06lu seconds\n", cp, diff, (unsigned long)sys_tv.tv_usec);
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}
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#endif
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}
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static void to_sys_clock(const char **pp_rtcname, int utc)
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{
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struct timeval tv;
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struct timezone tz;
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tz.tz_minuteswest = timezone/60 - 60*daylight;
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tz.tz_dsttime = 0;
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tv.tv_sec = read_rtc(pp_rtcname, NULL, utc);
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tv.tv_usec = 0;
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if (settimeofday(&tv, &tz))
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bb_perror_msg_and_die("settimeofday");
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}
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static void from_sys_clock(const char **pp_rtcname, int utc)
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{
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#if 1
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struct timeval tv;
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struct tm tm_time;
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int rtc;
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rtc = rtc_xopen(pp_rtcname, O_WRONLY);
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gettimeofday(&tv, NULL);
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/* Prepare tm_time */
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if (sizeof(time_t) == sizeof(tv.tv_sec)) {
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if (utc)
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gmtime_r((time_t*)&tv.tv_sec, &tm_time);
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else
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localtime_r((time_t*)&tv.tv_sec, &tm_time);
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} else {
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time_t t = tv.tv_sec;
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if (utc)
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gmtime_r(&t, &tm_time);
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else
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localtime_r(&t, &tm_time);
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}
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#else
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/* Bloated code which tries to set hw clock with better precision.
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* On x86, even though code does set hw clock within <1ms of exact
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* whole seconds, apparently hw clock (at least on some machines)
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* doesn't reset internal fractional seconds to 0,
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* making all this a pointless excercise.
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*/
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/* If we see that we are N usec away from whole second,
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* we'll sleep for N-ADJ usecs. ADJ corrects for the fact
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* that CPU is not infinitely fast.
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* On infinitely fast CPU, next wakeup would be
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* on (exactly_next_whole_second - ADJ). On real CPUs,
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* this difference between current time and whole second
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* is less than ADJ (assuming system isn't heavily loaded).
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*/
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/* Small value of 256us gives very precise sync for 2+ GHz CPUs.
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* Slower CPUs will fail to sync and will go to bigger
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* ADJ values. qemu-emulated armv4tl with ~100 MHz
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* performance ends up using ADJ ~= 4*1024 and it takes
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* 2+ secs (2 tries with successively larger ADJ)
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* to sync. Even straced one on the same qemu (very slow)
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* takes only 4 tries.
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*/
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#define TWEAK_USEC 256
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unsigned adj = TWEAK_USEC;
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struct tm tm_time;
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struct timeval tv;
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int rtc = rtc_xopen(pp_rtcname, O_WRONLY);
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/* Try to catch the moment when whole second is close */
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while (1) {
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unsigned rem_usec;
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time_t t;
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gettimeofday(&tv, NULL);
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t = tv.tv_sec;
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rem_usec = 1000000 - tv.tv_usec;
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if (rem_usec < adj) {
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/* Close enough */
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small_rem:
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t++;
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}
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/* Prepare tm_time from t */
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if (utc)
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gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */
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else
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localtime_r(&t, &tm_time); /* same */
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if (adj >= 32*1024) {
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break; /* 32 ms diff and still no luck?? give up trying to sync */
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}
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/* gmtime/localtime took some time, re-get cur time */
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gettimeofday(&tv, NULL);
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if (tv.tv_sec < t /* we are still in old second */
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|| (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */
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) {
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break; /* good, we are in sync! */
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}
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rem_usec = 1000000 - tv.tv_usec;
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if (rem_usec < adj) {
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t = tv.tv_sec;
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goto small_rem; /* already close to next sec, don't sleep */
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}
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/* Try to sync up by sleeping */
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usleep(rem_usec - adj);
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/* Jump to 1ms diff, then increase fast (x2): EVERY loop
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* takes ~1 sec, people won't like slowly converging code here!
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*/
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//bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec);
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if (adj < 512)
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adj = 512;
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/* ... and if last "overshoot" does not look insanely big,
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* just use it as adj increment. This makes convergence faster.
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*/
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if (tv.tv_usec < adj * 8) {
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adj += tv.tv_usec;
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continue;
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}
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adj *= 2;
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}
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/* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync.
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* Look for a value which makes tv_usec close to 999999 or 0.
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* For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200
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*/
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//bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec);
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#endif
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tm_time.tm_isdst = 0;
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xioctl(rtc, RTC_SET_TIME, &tm_time);
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if (ENABLE_FEATURE_CLEAN_UP)
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close(rtc);
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}
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#define HWCLOCK_OPT_LOCALTIME 0x01
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#define HWCLOCK_OPT_UTC 0x02
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#define HWCLOCK_OPT_SHOW 0x04
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#define HWCLOCK_OPT_HCTOSYS 0x08
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#define HWCLOCK_OPT_SYSTOHC 0x10
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#define HWCLOCK_OPT_RTCFILE 0x20
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int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int hwclock_main(int argc UNUSED_PARAM, char **argv)
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{
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const char *rtcname = NULL;
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unsigned opt;
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int utc;
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#if ENABLE_FEATURE_HWCLOCK_LONG_OPTIONS
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static const char hwclock_longopts[] ALIGN1 =
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"localtime\0" No_argument "l"
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"utc\0" No_argument "u"
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"show\0" No_argument "r"
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"hctosys\0" No_argument "s"
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"systohc\0" No_argument "w"
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"file\0" Required_argument "f"
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;
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applet_long_options = hwclock_longopts;
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#endif
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opt_complementary = "r--ws:w--rs:s--wr:l--u:u--l";
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opt = getopt32(argv, "lurswf:", &rtcname);
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/* If -u or -l wasn't given check if we are using utc */
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if (opt & (HWCLOCK_OPT_UTC | HWCLOCK_OPT_LOCALTIME))
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utc = (opt & HWCLOCK_OPT_UTC);
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else
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utc = rtc_adjtime_is_utc();
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if (opt & HWCLOCK_OPT_HCTOSYS)
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to_sys_clock(&rtcname, utc);
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else if (opt & HWCLOCK_OPT_SYSTOHC)
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from_sys_clock(&rtcname, utc);
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else
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/* default HWCLOCK_OPT_SHOW */
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show_clock(&rtcname, utc);
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return 0;
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}
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