diff options
Diffstat (limited to 'package/busybox/patches/000-upstream-hwclock.patch')
| -rw-r--r-- | package/busybox/patches/000-upstream-hwclock.patch | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/package/busybox/patches/000-upstream-hwclock.patch b/package/busybox/patches/000-upstream-hwclock.patch new file mode 100644 index 0000000000..971235db51 --- /dev/null +++ b/package/busybox/patches/000-upstream-hwclock.patch @@ -0,0 +1,151 @@ +--- 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); |