diff options
| -rw-r--r-- | arch/powerpc/Kconfig | 2 | ||||
| -rw-r--r-- | arch/powerpc/kernel/time.c | 68 |
2 files changed, 53 insertions, 17 deletions
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index b50d46d214f6..7ee79e0ac88e 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -155,7 +155,7 @@ config PPC select GENERIC_SMP_IDLE_THREAD select GENERIC_STRNCPY_FROM_USER select GENERIC_STRNLEN_USER - select GENERIC_TIME_VSYSCALL_OLD + select GENERIC_TIME_VSYSCALL select HAVE_ARCH_AUDITSYSCALL select HAVE_ARCH_JUMP_LABEL select HAVE_ARCH_KGDB diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 476a527b220d..0cc0dad905d5 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -841,28 +841,66 @@ static notrace u64 timebase_read(struct clocksource *cs) return (u64)get_tb(); } -void update_vsyscall_old(struct timespec *wall_time, struct timespec *wtm, - struct clocksource *clock, u32 mult, u64 cycle_last) + +void update_vsyscall(struct timekeeper *tk) { + struct timespec xt; + struct clocksource *clock = tk->tkr_mono.clock; + u32 mult = tk->tkr_mono.mult; + u32 shift = tk->tkr_mono.shift; + u64 cycle_last = tk->tkr_mono.cycle_last; u64 new_tb_to_xs, new_stamp_xsec; - u32 frac_sec; + u64 frac_sec; if (clock != &clocksource_timebase) return; + xt.tv_sec = tk->xtime_sec; + xt.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift); + /* Make userspace gettimeofday spin until we're done. */ ++vdso_data->tb_update_count; smp_mb(); - /* 19342813113834067 ~= 2^(20+64) / 1e9 */ - new_tb_to_xs = (u64) mult * (19342813113834067ULL >> clock->shift); - new_stamp_xsec = (u64) wall_time->tv_nsec * XSEC_PER_SEC; - do_div(new_stamp_xsec, 1000000000); - new_stamp_xsec += (u64) wall_time->tv_sec * XSEC_PER_SEC; + /* + * This computes ((2^20 / 1e9) * mult) >> shift as a + * 0.64 fixed-point fraction. + * The computation in the else clause below won't overflow + * (as long as the timebase frequency is >= 1.049 MHz) + * but loses precision because we lose the low bits of the constant + * in the shift. Note that 19342813113834067 ~= 2^(20+64) / 1e9. + * For a shift of 24 the error is about 0.5e-9, or about 0.5ns + * over a second. (Shift values are usually 22, 23 or 24.) + * For high frequency clocks such as the 512MHz timebase clock + * on POWER[6789], the mult value is small (e.g. 32768000) + * and so we can shift the constant by 16 initially + * (295147905179 ~= 2^(20+64-16) / 1e9) and then do the + * remaining shifts after the multiplication, which gives a + * more accurate result (e.g. with mult = 32768000, shift = 24, + * the error is only about 1.2e-12, or 0.7ns over 10 minutes). + */ + if (mult <= 62500000 && clock->shift >= 16) + new_tb_to_xs = ((u64) mult * 295147905179ULL) >> (clock->shift - 16); + else + new_tb_to_xs = (u64) mult * (19342813113834067ULL >> clock->shift); + + /* + * Compute the fractional second in units of 2^-32 seconds. + * The fractional second is tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift + * in nanoseconds, so multiplying that by 2^32 / 1e9 gives + * it in units of 2^-32 seconds. + * We assume shift <= 32 because clocks_calc_mult_shift() + * generates shift values in the range 0 - 32. + */ + frac_sec = tk->tkr_mono.xtime_nsec << (32 - shift); + do_div(frac_sec, NSEC_PER_SEC); - BUG_ON(wall_time->tv_nsec >= NSEC_PER_SEC); - /* this is tv_nsec / 1e9 as a 0.32 fraction */ - frac_sec = ((u64) wall_time->tv_nsec * 18446744073ULL) >> 32; + /* + * Work out new stamp_xsec value for any legacy users of systemcfg. + * stamp_xsec is in units of 2^-20 seconds. + */ + new_stamp_xsec = frac_sec >> 12; + new_stamp_xsec += tk->xtime_sec * XSEC_PER_SEC; /* * tb_update_count is used to allow the userspace gettimeofday code @@ -872,15 +910,13 @@ void update_vsyscall_old(struct timespec *wall_time, struct timespec *wtm, * the two values of tb_update_count match and are even then the * tb_to_xs and stamp_xsec values are consistent. If not, then it * loops back and reads them again until this criteria is met. - * We expect the caller to have done the first increment of - * vdso_data->tb_update_count already. */ vdso_data->tb_orig_stamp = cycle_last; vdso_data->stamp_xsec = new_stamp_xsec; vdso_data->tb_to_xs = new_tb_to_xs; - vdso_data->wtom_clock_sec = wtm->tv_sec; - vdso_data->wtom_clock_nsec = wtm->tv_nsec; - vdso_data->stamp_xtime = *wall_time; + vdso_data->wtom_clock_sec = tk->wall_to_monotonic.tv_sec; + vdso_data->wtom_clock_nsec = tk->wall_to_monotonic.tv_nsec; + vdso_data->stamp_xtime = xt; vdso_data->stamp_sec_fraction = frac_sec; smp_wmb(); ++(vdso_data->tb_update_count); |