time.c (6b847d795cf4ab3e574f4fcf7193fe245908a195) time.c (d4cfb11387ee29ba4626546c676fd25c7abbbbb2)
1/*
2 * Common time routines among all ppc machines.
3 *
4 * Written by Cort Dougan (cort@cs.nmt.edu) to merge
5 * Paul Mackerras' version and mine for PReP and Pmac.
6 * MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net).
7 * Converted for 64-bit by Mike Corrigan (mikejc@us.ibm.com)
8 *

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836 return (u64)get_rtc();
837}
838
839static notrace u64 timebase_read(struct clocksource *cs)
840{
841 return (u64)get_tb();
842}
843
1/*
2 * Common time routines among all ppc machines.
3 *
4 * Written by Cort Dougan (cort@cs.nmt.edu) to merge
5 * Paul Mackerras' version and mine for PReP and Pmac.
6 * MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net).
7 * Converted for 64-bit by Mike Corrigan (mikejc@us.ibm.com)
8 *

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836 return (u64)get_rtc();
837}
838
839static notrace u64 timebase_read(struct clocksource *cs)
840{
841 return (u64)get_tb();
842}
843
844void update_vsyscall_old(struct timespec *wall_time, struct timespec *wtm,
845 struct clocksource *clock, u32 mult, u64 cycle_last)
844
845void update_vsyscall(struct timekeeper *tk)
846{
846{
847 struct timespec xt;
848 struct clocksource *clock = tk->tkr_mono.clock;
849 u32 mult = tk->tkr_mono.mult;
850 u32 shift = tk->tkr_mono.shift;
851 u64 cycle_last = tk->tkr_mono.cycle_last;
847 u64 new_tb_to_xs, new_stamp_xsec;
852 u64 new_tb_to_xs, new_stamp_xsec;
848 u32 frac_sec;
853 u64 frac_sec;
849
850 if (clock != &clocksource_timebase)
851 return;
852
854
855 if (clock != &clocksource_timebase)
856 return;
857
858 xt.tv_sec = tk->xtime_sec;
859 xt.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
860
853 /* Make userspace gettimeofday spin until we're done. */
854 ++vdso_data->tb_update_count;
855 smp_mb();
856
861 /* Make userspace gettimeofday spin until we're done. */
862 ++vdso_data->tb_update_count;
863 smp_mb();
864
857 /* 19342813113834067 ~= 2^(20+64) / 1e9 */
858 new_tb_to_xs = (u64) mult * (19342813113834067ULL >> clock->shift);
859 new_stamp_xsec = (u64) wall_time->tv_nsec * XSEC_PER_SEC;
860 do_div(new_stamp_xsec, 1000000000);
861 new_stamp_xsec += (u64) wall_time->tv_sec * XSEC_PER_SEC;
865 /*
866 * This computes ((2^20 / 1e9) * mult) >> shift as a
867 * 0.64 fixed-point fraction.
868 * The computation in the else clause below won't overflow
869 * (as long as the timebase frequency is >= 1.049 MHz)
870 * but loses precision because we lose the low bits of the constant
871 * in the shift. Note that 19342813113834067 ~= 2^(20+64) / 1e9.
872 * For a shift of 24 the error is about 0.5e-9, or about 0.5ns
873 * over a second. (Shift values are usually 22, 23 or 24.)
874 * For high frequency clocks such as the 512MHz timebase clock
875 * on POWER[6789], the mult value is small (e.g. 32768000)
876 * and so we can shift the constant by 16 initially
877 * (295147905179 ~= 2^(20+64-16) / 1e9) and then do the
878 * remaining shifts after the multiplication, which gives a
879 * more accurate result (e.g. with mult = 32768000, shift = 24,
880 * the error is only about 1.2e-12, or 0.7ns over 10 minutes).
881 */
882 if (mult <= 62500000 && clock->shift >= 16)
883 new_tb_to_xs = ((u64) mult * 295147905179ULL) >> (clock->shift - 16);
884 else
885 new_tb_to_xs = (u64) mult * (19342813113834067ULL >> clock->shift);
862
886
863 BUG_ON(wall_time->tv_nsec >= NSEC_PER_SEC);
864 /* this is tv_nsec / 1e9 as a 0.32 fraction */
865 frac_sec = ((u64) wall_time->tv_nsec * 18446744073ULL) >> 32;
887 /*
888 * Compute the fractional second in units of 2^-32 seconds.
889 * The fractional second is tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift
890 * in nanoseconds, so multiplying that by 2^32 / 1e9 gives
891 * it in units of 2^-32 seconds.
892 * We assume shift <= 32 because clocks_calc_mult_shift()
893 * generates shift values in the range 0 - 32.
894 */
895 frac_sec = tk->tkr_mono.xtime_nsec << (32 - shift);
896 do_div(frac_sec, NSEC_PER_SEC);
866
867 /*
897
898 /*
899 * Work out new stamp_xsec value for any legacy users of systemcfg.
900 * stamp_xsec is in units of 2^-20 seconds.
901 */
902 new_stamp_xsec = frac_sec >> 12;
903 new_stamp_xsec += tk->xtime_sec * XSEC_PER_SEC;
904
905 /*
868 * tb_update_count is used to allow the userspace gettimeofday code
869 * to assure itself that it sees a consistent view of the tb_to_xs and
870 * stamp_xsec variables. It reads the tb_update_count, then reads
871 * tb_to_xs and stamp_xsec and then reads tb_update_count again. If
872 * the two values of tb_update_count match and are even then the
873 * tb_to_xs and stamp_xsec values are consistent. If not, then it
874 * loops back and reads them again until this criteria is met.
906 * tb_update_count is used to allow the userspace gettimeofday code
907 * to assure itself that it sees a consistent view of the tb_to_xs and
908 * stamp_xsec variables. It reads the tb_update_count, then reads
909 * tb_to_xs and stamp_xsec and then reads tb_update_count again. If
910 * the two values of tb_update_count match and are even then the
911 * tb_to_xs and stamp_xsec values are consistent. If not, then it
912 * loops back and reads them again until this criteria is met.
875 * We expect the caller to have done the first increment of
876 * vdso_data->tb_update_count already.
877 */
878 vdso_data->tb_orig_stamp = cycle_last;
879 vdso_data->stamp_xsec = new_stamp_xsec;
880 vdso_data->tb_to_xs = new_tb_to_xs;
913 */
914 vdso_data->tb_orig_stamp = cycle_last;
915 vdso_data->stamp_xsec = new_stamp_xsec;
916 vdso_data->tb_to_xs = new_tb_to_xs;
881 vdso_data->wtom_clock_sec = wtm->tv_sec;
882 vdso_data->wtom_clock_nsec = wtm->tv_nsec;
883 vdso_data->stamp_xtime = *wall_time;
917 vdso_data->wtom_clock_sec = tk->wall_to_monotonic.tv_sec;
918 vdso_data->wtom_clock_nsec = tk->wall_to_monotonic.tv_nsec;
919 vdso_data->stamp_xtime = xt;
884 vdso_data->stamp_sec_fraction = frac_sec;
885 smp_wmb();
886 ++(vdso_data->tb_update_count);
887}
888
889void update_vsyscall_tz(void)
890{
891 vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;

--- 342 unchanged lines hidden --- 		920 vdso_data->stamp_sec_fraction = frac_sec;
921 smp_wmb();
922 ++(vdso_data->tb_update_count);
923}
924
925void update_vsyscall_tz(void)
926{
927 vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;

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