---- a/util-linux/hwclock.c
-+++ b/util-linux/hwclock.c
-@@ -109,10 +109,53 @@ static void to_sys_clock(const char **pp
-
- static void from_sys_clock(const char **pp_rtcname, int utc)
- {
--#define TWEAK_USEC 200
-- struct tm tm_time;
-+#if 1
- struct timeval tv;
-+ struct tm tm_time;
-+ int rtc;
-+
-+ rtc = rtc_xopen(pp_rtcname, O_WRONLY);
-+ gettimeofday(&tv, NULL);
-+ /* Prepare tm_time */
-+ if (sizeof(time_t) == sizeof(tv.tv_sec)) {
-+ if (utc)
-+ gmtime_r((time_t*)&tv.tv_sec, &tm_time);
-+ else
-+ localtime_r((time_t*)&tv.tv_sec, &tm_time);
-+ } else {
-+ time_t t = tv.tv_sec;
-+ if (utc)
-+ gmtime_r(&t, &tm_time);
-+ else
-+ localtime_r(&t, &tm_time);
-+ }
-+#else
-+/* Bloated code which tries to set hw clock with better precision.
-+ * On x86, even though code does set hw clock within <1ms of exact
-+ * whole seconds, apparently hw clock (at least on some machines)
-+ * doesn't reset internal fractional seconds to 0,
-+ * making all this a pointless excercise.
-+ */
-+ /* If we see that we are N usec away from whole second,
-+ * we'll sleep for N-ADJ usecs. ADJ corrects for the fact
-+ * that CPU is not infinitely fast.
-+ * On infinitely fast CPU, next wakeup would be
-+ * on (exactly_next_whole_second - ADJ). On real CPUs,
-+ * this difference between current time and whole second
-+ * is less than ADJ (assuming system isn't heavily loaded).
-+ */
-+ /* Small value of 256us gives very precise sync for 2+ GHz CPUs.
-+ * Slower CPUs will fail to sync and will go to bigger
-+ * ADJ values. qemu-emulated armv4tl with ~100 MHz
-+ * performance ends up using ADJ ~= 4*1024 and it takes
-+ * 2+ secs (2 tries with successively larger ADJ)
-+ * to sync. Even straced one on the same qemu (very slow)
-+ * takes only 4 tries.
-+ */
-+#define TWEAK_USEC 256
- unsigned adj = TWEAK_USEC;
-+ struct tm tm_time;
-+ struct timeval tv;
- int rtc = rtc_xopen(pp_rtcname, O_WRONLY);
-
- /* Try to catch the moment when whole second is close */
-@@ -124,55 +167,64 @@ static void from_sys_clock(const char **
-
- t = tv.tv_sec;
- rem_usec = 1000000 - tv.tv_usec;
-- if (rem_usec < 1024) {
-- /* Less than 1ms to next second. Good enough */
-+ if (rem_usec < adj) {
-+ /* Close enough */
- small_rem:
- t++;
- }
-
-- /* Prepare tm */
-+ /* Prepare tm_time from t */
- if (utc)
- gmtime_r(&t, &tm_time); /* may read /etc/xxx (it takes time) */
- else
- localtime_r(&t, &tm_time); /* same */
-- tm_time.tm_isdst = 0;
-+
-+ if (adj >= 32*1024) {
-+ break; /* 32 ms diff and still no luck?? give up trying to sync */
-+ }
-
- /* gmtime/localtime took some time, re-get cur time */
- gettimeofday(&tv, NULL);
-
-- if (tv.tv_sec < t /* may happen if rem_usec was < 1024 */
-- || (tv.tv_sec == t && tv.tv_usec < 1024)
-+ if (tv.tv_sec < t /* we are still in old second */
-+ || (tv.tv_sec == t && tv.tv_usec < adj) /* not too far into next second */
- ) {
-- /* We are not too far into next second. Good. */
-- break;
-- }
-- adj += 32; /* 2^(10-5) = 2^5 = 32 iterations max */
-- if (adj >= 1024) {
-- /* Give up trying to sync */
-- break;
-+ break; /* good, we are in sync! */
- }
-
-- /* Try to sync up by sleeping */
- rem_usec = 1000000 - tv.tv_usec;
-- if (rem_usec < 1024) {
-- goto small_rem; /* already close, don't sleep */
-+ if (rem_usec < adj) {
-+ t = tv.tv_sec;
-+ goto small_rem; /* already close to next sec, don't sleep */
- }
-- /* Need to sleep.
-- * Note that small adj on slow processors can make us
-- * to always overshoot tv.tv_usec < 1024 check on next
-- * iteration. That's why adj is increased on each iteration.
-- * This also allows it to be reused as a loop limiter.
-- */
-- usleep(rem_usec - adj);
-- }
-
-- xioctl(rtc, RTC_SET_TIME, &tm_time);
-+ /* Try to sync up by sleeping */
-+ usleep(rem_usec - adj);
-
-- /* Debug aid to find "good" TWEAK_USEC.
-+ /* Jump to 1ms diff, then increase fast (x2): EVERY loop
-+ * takes ~1 sec, people won't like slowly converging code here!
-+ */
-+ //bb_error_msg("adj:%d tv.tv_usec:%d", adj, (int)tv.tv_usec);
-+ if (adj < 512)
-+ adj = 512;
-+ /* ... and if last "overshoot" does not look insanely big,
-+ * just use it as adj increment. This makes convergence faster.
-+ */
-+ if (tv.tv_usec < adj * 8) {
-+ adj += tv.tv_usec;
-+ continue;
-+ }
-+ adj *= 2;
-+ }
-+ /* Debug aid to find "optimal" TWEAK_USEC with nearly exact sync.
- * Look for a value which makes tv_usec close to 999999 or 0.
-- * for 2.20GHz Intel Core 2: TWEAK_USEC ~= 200
-+ * For 2.20GHz Intel Core 2: optimal TWEAK_USEC ~= 200
- */
-- //bb_error_msg("tv.tv_usec:%d adj:%d", (int)tv.tv_usec, adj);
-+ //bb_error_msg("tv.tv_usec:%d", (int)tv.tv_usec);
-+#endif
-+
-+ tm_time.tm_isdst = 0;
-+ xioctl(rtc, RTC_SET_TIME, &tm_time);
-
- if (ENABLE_FEATURE_CLEAN_UP)
- close(rtc);
projects / openwrt.git / commitdiff