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Diffstat (limited to 'arch/ppc64/kernel/time.c')
| -rw-r--r-- | arch/ppc64/kernel/time.c | 827 |
1 files changed, 827 insertions, 0 deletions
diff --git a/arch/ppc64/kernel/time.c b/arch/ppc64/kernel/time.c new file mode 100644 index 00000000000..77ded5a363b --- /dev/null +++ b/arch/ppc64/kernel/time.c @@ -0,0 +1,827 @@ +/* + * + * Common time routines among all ppc machines. + * + * Written by Cort Dougan (cort@cs.nmt.edu) to merge + * Paul Mackerras' version and mine for PReP and Pmac. + * MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net). + * Converted for 64-bit by Mike Corrigan (mikejc@us.ibm.com) + * + * First round of bugfixes by Gabriel Paubert (paubert@iram.es) + * to make clock more stable (2.4.0-test5). The only thing + * that this code assumes is that the timebases have been synchronized + * by firmware on SMP and are never stopped (never do sleep + * on SMP then, nap and doze are OK). + * + * Speeded up do_gettimeofday by getting rid of references to + * xtime (which required locks for consistency). (mikejc@us.ibm.com) + * + * TODO (not necessarily in this file): + * - improve precision and reproducibility of timebase frequency + * measurement at boot time. (for iSeries, we calibrate the timebase + * against the Titan chip's clock.) + * - for astronomical applications: add a new function to get + * non ambiguous timestamps even around leap seconds. This needs + * a new timestamp format and a good name. + * + * 1997-09-10 Updated NTP code according to technical memorandum Jan '96 + * "A Kernel Model for Precision Timekeeping" by Dave Mills + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <linux/config.h> +#include <linux/errno.h> +#include <linux/module.h> +#include <linux/sched.h> +#include <linux/kernel.h> +#include <linux/param.h> +#include <linux/string.h> +#include <linux/mm.h> +#include <linux/interrupt.h> +#include <linux/timex.h> +#include <linux/kernel_stat.h> +#include <linux/mc146818rtc.h> +#include <linux/time.h> +#include <linux/init.h> +#include <linux/profile.h> +#include <linux/cpu.h> +#include <linux/security.h> + +#include <asm/segment.h> +#include <asm/io.h> +#include <asm/processor.h> +#include <asm/nvram.h> +#include <asm/cache.h> +#include <asm/machdep.h> +#ifdef CONFIG_PPC_ISERIES +#include <asm/iSeries/ItLpQueue.h> +#include <asm/iSeries/HvCallXm.h> +#endif +#include <asm/uaccess.h> +#include <asm/time.h> +#include <asm/ppcdebug.h> +#include <asm/prom.h> +#include <asm/sections.h> +#include <asm/systemcfg.h> + +u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES; + +EXPORT_SYMBOL(jiffies_64); + +/* keep track of when we need to update the rtc */ +time_t last_rtc_update; +extern int piranha_simulator; +#ifdef CONFIG_PPC_ISERIES +unsigned long iSeries_recal_titan = 0; +unsigned long iSeries_recal_tb = 0; +static unsigned long first_settimeofday = 1; +#endif + +#define XSEC_PER_SEC (1024*1024) + +unsigned long tb_ticks_per_jiffy; +unsigned long tb_ticks_per_usec = 100; /* sane default */ +EXPORT_SYMBOL(tb_ticks_per_usec); +unsigned long tb_ticks_per_sec; +unsigned long tb_to_xs; +unsigned tb_to_us; +unsigned long processor_freq; +DEFINE_SPINLOCK(rtc_lock); + +unsigned long tb_to_ns_scale; +unsigned long tb_to_ns_shift; + +struct gettimeofday_struct do_gtod; + +extern unsigned long wall_jiffies; +extern unsigned long lpevent_count; +extern int smp_tb_synchronized; + +extern struct timezone sys_tz; + +void ppc_adjtimex(void); + +static unsigned adjusting_time = 0; + +static __inline__ void timer_check_rtc(void) +{ + /* + * update the rtc when needed, this should be performed on the + * right fraction of a second. Half or full second ? + * Full second works on mk48t59 clocks, others need testing. + * Note that this update is basically only used through + * the adjtimex system calls. Setting the HW clock in + * any other way is a /dev/rtc and userland business. + * This is still wrong by -0.5/+1.5 jiffies because of the + * timer interrupt resolution and possible delay, but here we + * hit a quantization limit which can only be solved by higher + * resolution timers and decoupling time management from timer + * interrupts. This is also wrong on the clocks + * which require being written at the half second boundary. + * We should have an rtc call that only sets the minutes and + * seconds like on Intel to avoid problems with non UTC clocks. + */ + if ( (time_status & STA_UNSYNC) == 0 && + xtime.tv_sec - last_rtc_update >= 659 && + abs((xtime.tv_nsec/1000) - (1000000-1000000/HZ)) < 500000/HZ && + jiffies - wall_jiffies == 1) { + struct rtc_time tm; + to_tm(xtime.tv_sec+1, &tm); + tm.tm_year -= 1900; + tm.tm_mon -= 1; + if (ppc_md.set_rtc_time(&tm) == 0) + last_rtc_update = xtime.tv_sec+1; + else + /* Try again one minute later */ + last_rtc_update += 60; + } +} + +/* + * This version of gettimeofday has microsecond resolution. + */ +static inline void __do_gettimeofday(struct timeval *tv, unsigned long tb_val) +{ + unsigned long sec, usec, tb_ticks; + unsigned long xsec, tb_xsec; + struct gettimeofday_vars * temp_varp; + unsigned long temp_tb_to_xs, temp_stamp_xsec; + + /* + * These calculations are faster (gets rid of divides) + * if done in units of 1/2^20 rather than microseconds. + * The conversion to microseconds at the end is done + * without a divide (and in fact, without a multiply) + */ + temp_varp = do_gtod.varp; + tb_ticks = tb_val - temp_varp->tb_orig_stamp; + temp_tb_to_xs = temp_varp->tb_to_xs; + temp_stamp_xsec = temp_varp->stamp_xsec; + tb_xsec = mulhdu( tb_ticks, temp_tb_to_xs ); + xsec = temp_stamp_xsec + tb_xsec; + sec = xsec / XSEC_PER_SEC; + xsec -= sec * XSEC_PER_SEC; + usec = (xsec * USEC_PER_SEC)/XSEC_PER_SEC; + + tv->tv_sec = sec; + tv->tv_usec = usec; +} + +void do_gettimeofday(struct timeval *tv) +{ + __do_gettimeofday(tv, get_tb()); +} + +EXPORT_SYMBOL(do_gettimeofday); + +/* Synchronize xtime with do_gettimeofday */ + +static inline void timer_sync_xtime(unsigned long cur_tb) +{ + struct timeval my_tv; + + __do_gettimeofday(&my_tv, cur_tb); + + if (xtime.tv_sec <= my_tv.tv_sec) { + xtime.tv_sec = my_tv.tv_sec; + xtime.tv_nsec = my_tv.tv_usec * 1000; + } +} + +/* + * When the timebase - tb_orig_stamp gets too big, we do a manipulation + * between tb_orig_stamp and stamp_xsec. The goal here is to keep the + * difference tb - tb_orig_stamp small enough to always fit inside a + * 32 bits number. This is a requirement of our fast 32 bits userland + * implementation in the vdso. If we "miss" a call to this function + * (interrupt latency, CPU locked in a spinlock, ...) and we end up + * with a too big difference, then the vdso will fallback to calling + * the syscall + */ +static __inline__ void timer_recalc_offset(unsigned long cur_tb) +{ + struct gettimeofday_vars * temp_varp; + unsigned temp_idx; + unsigned long offset, new_stamp_xsec, new_tb_orig_stamp; + + if (((cur_tb - do_gtod.varp->tb_orig_stamp) & 0x80000000u) == 0) + return; + + temp_idx = (do_gtod.var_idx == 0); + temp_varp = &do_gtod.vars[temp_idx]; + + new_tb_orig_stamp = cur_tb; + offset = new_tb_orig_stamp - do_gtod.varp->tb_orig_stamp; + new_stamp_xsec = do_gtod.varp->stamp_xsec + mulhdu(offset, do_gtod.varp->tb_to_xs); + + temp_varp->tb_to_xs = do_gtod.varp->tb_to_xs; + temp_varp->tb_orig_stamp = new_tb_orig_stamp; + temp_varp->stamp_xsec = new_stamp_xsec; + mb(); + do_gtod.varp = temp_varp; + do_gtod.var_idx = temp_idx; + + ++(systemcfg->tb_update_count); + wmb(); + systemcfg->tb_orig_stamp = new_tb_orig_stamp; + systemcfg->stamp_xsec = new_stamp_xsec; + wmb(); + ++(systemcfg->tb_update_count); +} + +#ifdef CONFIG_SMP +unsigned long profile_pc(struct pt_regs *regs) +{ + unsigned long pc = instruction_pointer(regs); + + if (in_lock_functions(pc)) + return regs->link; + + return pc; +} +EXPORT_SYMBOL(profile_pc); +#endif + +#ifdef CONFIG_PPC_ISERIES + +/* + * This function recalibrates the timebase based on the 49-bit time-of-day + * value in the Titan chip. The Titan is much more accurate than the value + * returned by the service processor for the timebase frequency. + */ + +static void iSeries_tb_recal(void) +{ + struct div_result divres; + unsigned long titan, tb; + tb = get_tb(); + titan = HvCallXm_loadTod(); + if ( iSeries_recal_titan ) { + unsigned long tb_ticks = tb - iSeries_recal_tb; + unsigned long titan_usec = (titan - iSeries_recal_titan) >> 12; + unsigned long new_tb_ticks_per_sec = (tb_ticks * USEC_PER_SEC)/titan_usec; + unsigned long new_tb_ticks_per_jiffy = (new_tb_ticks_per_sec+(HZ/2))/HZ; + long tick_diff = new_tb_ticks_per_jiffy - tb_ticks_per_jiffy; + char sign = '+'; + /* make sure tb_ticks_per_sec and tb_ticks_per_jiffy are consistent */ + new_tb_ticks_per_sec = new_tb_ticks_per_jiffy * HZ; + + if ( tick_diff < 0 ) { + tick_diff = -tick_diff; + sign = '-'; + } + if ( tick_diff ) { + if ( tick_diff < tb_ticks_per_jiffy/25 ) { + printk( "Titan recalibrate: new tb_ticks_per_jiffy = %lu (%c%ld)\n", + new_tb_ticks_per_jiffy, sign, tick_diff ); + tb_ticks_per_jiffy = new_tb_ticks_per_jiffy; + tb_ticks_per_sec = new_tb_ticks_per_sec; + div128_by_32( XSEC_PER_SEC, 0, tb_ticks_per_sec, &divres ); + do_gtod.tb_ticks_per_sec = tb_ticks_per_sec; + tb_to_xs = divres.result_low; + do_gtod.varp->tb_to_xs = tb_to_xs; + systemcfg->tb_ticks_per_sec = tb_ticks_per_sec; + systemcfg->tb_to_xs = tb_to_xs; + } + else { + printk( "Titan recalibrate: FAILED (difference > 4 percent)\n" + " new tb_ticks_per_jiffy = %lu\n" + " old tb_ticks_per_jiffy = %lu\n", + new_tb_ticks_per_jiffy, tb_ticks_per_jiffy ); + } + } + } + iSeries_recal_titan = titan; + iSeries_recal_tb = tb; +} +#endif + +/* + * For iSeries shared processors, we have to let the hypervisor + * set the hardware decrementer. We set a virtual decrementer + * in the lppaca and call the hypervisor if the virtual + * decrementer is less than the current value in the hardware + * decrementer. (almost always the new decrementer value will + * be greater than the current hardware decementer so the hypervisor + * call will not be needed) + */ + +unsigned long tb_last_stamp __cacheline_aligned_in_smp; + +/* + * timer_interrupt - gets called when the decrementer overflows, + * with interrupts disabled. + */ +int timer_interrupt(struct pt_regs * regs) +{ + int next_dec; + unsigned long cur_tb; + struct paca_struct *lpaca = get_paca(); + unsigned long cpu = smp_processor_id(); + + irq_enter(); + +#ifndef CONFIG_PPC_ISERIES + profile_tick(CPU_PROFILING, regs); +#endif + + lpaca->lppaca.int_dword.fields.decr_int = 0; + + while (lpaca->next_jiffy_update_tb <= (cur_tb = get_tb())) { + /* + * We cannot disable the decrementer, so in the period + * between this cpu's being marked offline in cpu_online_map + * and calling stop-self, it is taking timer interrupts. + * Avoid calling into the scheduler rebalancing code if this + * is the case. + */ + if (!cpu_is_offline(cpu)) + update_process_times(user_mode(regs)); + /* + * No need to check whether cpu is offline here; boot_cpuid + * should have been fixed up by now. + */ + if (cpu == boot_cpuid) { + write_seqlock(&xtime_lock); + tb_last_stamp = lpaca->next_jiffy_update_tb; + timer_recalc_offset(lpaca->next_jiffy_update_tb); + do_timer(regs); + timer_sync_xtime(lpaca->next_jiffy_update_tb); + timer_check_rtc(); + write_sequnlock(&xtime_lock); + if ( adjusting_time && (time_adjust == 0) ) + ppc_adjtimex(); + } + lpaca->next_jiffy_update_tb += tb_ticks_per_jiffy; + } + + next_dec = lpaca->next_jiffy_update_tb - cur_tb; + if (next_dec > lpaca->default_decr) + next_dec = lpaca->default_decr; + set_dec(next_dec); + +#ifdef CONFIG_PPC_ISERIES + { + struct ItLpQueue *lpq = lpaca->lpqueue_ptr; + if (lpq && ItLpQueue_isLpIntPending(lpq)) + lpevent_count += ItLpQueue_process(lpq, regs); + } +#endif + +/* collect purr register values often, for accurate calculations */ +#if defined(CONFIG_PPC_PSERIES) + if (cur_cpu_spec->firmware_features & FW_FEATURE_SPLPAR) { + struct cpu_usage *cu = &__get_cpu_var(cpu_usage_array); + cu->current_tb = mfspr(SPRN_PURR); + } +#endif + + irq_exit(); + + return 1; +} + +/* + * Scheduler clock - returns current time in nanosec units. + * + * Note: mulhdu(a, b) (multiply high double unsigned) returns + * the high 64 bits of a * b, i.e. (a * b) >> 64, where a and b + * are 64-bit unsigned numbers. + */ +unsigned long long sched_clock(void) +{ + return mulhdu(get_tb(), tb_to_ns_scale) << tb_to_ns_shift; +} + +int do_settimeofday(struct timespec *tv) +{ + time_t wtm_sec, new_sec = tv->tv_sec; + long wtm_nsec, new_nsec = tv->tv_nsec; + unsigned long flags; + unsigned long delta_xsec; + long int tb_delta; + unsigned long new_xsec; + + if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) + return -EINVAL; + + write_seqlock_irqsave(&xtime_lock, flags); + /* Updating the RTC is not the job of this code. If the time is + * stepped under NTP, the RTC will be update after STA_UNSYNC + * is cleared. Tool like clock/hwclock either copy the RTC + * to the system time, in which case there is no point in writing + * to the RTC again, or write to the RTC but then they don't call + * settimeofday to perform this operation. + */ +#ifdef CONFIG_PPC_ISERIES + if ( first_settimeofday ) { + iSeries_tb_recal(); + first_settimeofday = 0; + } +#endif + tb_delta = tb_ticks_since(tb_last_stamp); + tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy; + + new_nsec -= tb_delta / tb_ticks_per_usec / 1000; + + wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - new_sec); + wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - new_nsec); + + set_normalized_timespec(&xtime, new_sec, new_nsec); + set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec); + + /* In case of a large backwards jump in time with NTP, we want the + * clock to be updated as soon as the PLL is again in lock. + */ + last_rtc_update = new_sec - 658; + + time_adjust = 0; /* stop active adjtime() */ + time_status |= STA_UNSYNC; + time_maxerror = NTP_PHASE_LIMIT; + time_esterror = NTP_PHASE_LIMIT; + + delta_xsec = mulhdu( (tb_last_stamp-do_gtod.varp->tb_orig_stamp), + do_gtod.varp->tb_to_xs ); + + new_xsec = (new_nsec * XSEC_PER_SEC) / NSEC_PER_SEC; + new_xsec += new_sec * XSEC_PER_SEC; + if ( new_xsec > delta_xsec ) { + do_gtod.varp->stamp_xsec = new_xsec - delta_xsec; + systemcfg->stamp_xsec = new_xsec - delta_xsec; + } + else { + /* This is only for the case where the user is setting the time + * way back to a time such that the boot time would have been + * before 1970 ... eg. we booted ten days ago, and we are setting + * the time to Jan 5, 1970 */ + do_gtod.varp->stamp_xsec = new_xsec; + do_gtod.varp->tb_orig_stamp = tb_last_stamp; + systemcfg->stamp_xsec = new_xsec; + systemcfg->tb_orig_stamp = tb_last_stamp; + } + + systemcfg->tz_minuteswest = sys_tz.tz_minuteswest; + systemcfg->tz_dsttime = sys_tz.tz_dsttime; + + write_sequnlock_irqrestore(&xtime_lock, flags); + clock_was_set(); + return 0; +} + +EXPORT_SYMBOL(do_settimeofday); + +void __init time_init(void) +{ + /* This function is only called on the boot processor */ + unsigned long flags; + struct rtc_time tm; + struct div_result res; + unsigned long scale, shift; + + ppc_md.calibrate_decr(); + + /* + * Compute scale factor for sched_clock. + * The calibrate_decr() function has set tb_ticks_per_sec, + * which is the timebase frequency. + * We compute 1e9 * 2^64 / tb_ticks_per_sec and interpret + * the 128-bit result as a 64.64 fixed-point number. + * We then shift that number right until it is less than 1.0, + * giving us the scale factor and shift count to use in + * sched_clock(). + */ + div128_by_32(1000000000, 0, tb_ticks_per_sec, &res); + scale = res.result_low; + for (shift = 0; res.result_high != 0; ++shift) { + scale = (scale >> 1) | (res.result_high << 63); + res.result_high >>= 1; + } + tb_to_ns_scale = scale; + tb_to_ns_shift = shift; + +#ifdef CONFIG_PPC_ISERIES + if (!piranha_simulator) +#endif + ppc_md.get_boot_time(&tm); + + write_seqlock_irqsave(&xtime_lock, flags); + xtime.tv_sec = mktime(tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, + tm.tm_hour, tm.tm_min, tm.tm_sec); + tb_last_stamp = get_tb(); + do_gtod.varp = &do_gtod.vars[0]; + do_gtod.var_idx = 0; + do_gtod.varp->tb_orig_stamp = tb_last_stamp; + do_gtod.varp->stamp_xsec = xtime.tv_sec * XSEC_PER_SEC; + do_gtod.tb_ticks_per_sec = tb_ticks_per_sec; + do_gtod.varp->tb_to_xs = tb_to_xs; + do_gtod.tb_to_us = tb_to_us; + systemcfg->tb_orig_stamp = tb_last_stamp; + systemcfg->tb_update_count = 0; + systemcfg->tb_ticks_per_sec = tb_ticks_per_sec; + systemcfg->stamp_xsec = xtime.tv_sec * XSEC_PER_SEC; + systemcfg->tb_to_xs = tb_to_xs; + + time_freq = 0; + + xtime.tv_nsec = 0; + last_rtc_update = xtime.tv_sec; + set_normalized_timespec(&wall_to_monotonic, + -xtime.tv_sec, -xtime.tv_nsec); + write_sequnlock_irqrestore(&xtime_lock, flags); + + /* Not exact, but the timer interrupt takes care of this */ + set_dec(tb_ticks_per_jiffy); +} + +/* + * After adjtimex is called, adjust the conversion of tb ticks + * to microseconds to keep do_gettimeofday synchronized + * with ntpd. + * + * Use the time_adjust, time_freq and time_offset computed by adjtimex to + * adjust the frequency. + */ + +/* #define DEBUG_PPC_ADJTIMEX 1 */ + +void ppc_adjtimex(void) +{ + unsigned long den, new_tb_ticks_per_sec, tb_ticks, old_xsec, new_tb_to_xs, new_xsec, new_stamp_xsec; + unsigned long tb_ticks_per_sec_delta; + long delta_freq, ltemp; + struct div_result divres; + unsigned long flags; + struct gettimeofday_vars * temp_varp; + unsigned temp_idx; + long singleshot_ppm = 0; + + /* Compute parts per million frequency adjustment to accomplish the time adjustment + implied by time_offset to be applied over the elapsed time indicated by time_constant. + Use SHIFT_USEC to get it into the same units as time_freq. */ + if ( time_offset < 0 ) { + ltemp = -time_offset; + ltemp <<= SHIFT_USEC - SHIFT_UPDATE; + ltemp >>= SHIFT_KG + time_constant; + ltemp = -ltemp; + } + else { + ltemp = time_offset; + ltemp <<= SHIFT_USEC - SHIFT_UPDATE; + ltemp >>= SHIFT_KG + time_constant; + } + + /* If there is a single shot time adjustment in progress */ + if ( time_adjust ) { +#ifdef DEBUG_PPC_ADJTIMEX + printk("ppc_adjtimex: "); + if ( adjusting_time == 0 ) + printk("starting "); + printk("single shot time_adjust = %ld\n", time_adjust); +#endif + + adjusting_time = 1; + + /* Compute parts per million frequency adjustment to match time_adjust */ + singleshot_ppm = tickadj * HZ; + /* + * The adjustment should be tickadj*HZ to match the code in + * linux/kernel/timer.c, but experiments show that this is too + * large. 3/4 of tickadj*HZ seems about right + */ + singleshot_ppm -= singleshot_ppm / 4; + /* Use SHIFT_USEC to get it into the same units as time_freq */ + singleshot_ppm <<= SHIFT_USEC; + if ( time_adjust < 0 ) + singleshot_ppm = -singleshot_ppm; + } + else { +#ifdef DEBUG_PPC_ADJTIMEX + if ( adjusting_time ) + printk("ppc_adjtimex: ending single shot time_adjust\n"); +#endif + adjusting_time = 0; + } + + /* Add up all of the frequency adjustments */ + delta_freq = time_freq + ltemp + singleshot_ppm; + + /* Compute a new value for tb_ticks_per_sec based on the frequency adjustment */ + den = 1000000 * (1 << (SHIFT_USEC - 8)); + if ( delta_freq < 0 ) { + tb_ticks_per_sec_delta = ( tb_ticks_per_sec * ( (-delta_freq) >> (SHIFT_USEC - 8))) / den; + new_tb_ticks_per_sec = tb_ticks_per_sec + tb_ticks_per_sec_delta; + } + else { + tb_ticks_per_sec_delta = ( tb_ticks_per_sec * ( delta_freq >> (SHIFT_USEC - 8))) / den; + new_tb_ticks_per_sec = tb_ticks_per_sec - tb_ticks_per_sec_delta; + } + +#ifdef DEBUG_PPC_ADJTIMEX + printk("ppc_adjtimex: ltemp = %ld, time_freq = %ld, singleshot_ppm = %ld\n", ltemp, time_freq, singleshot_ppm); + printk("ppc_adjtimex: tb_ticks_per_sec - base = %ld new = %ld\n", tb_ticks_per_sec, new_tb_ticks_per_sec); +#endif + + /* Compute a new value of tb_to_xs (used to convert tb to microseconds and a new value of + stamp_xsec which is the time (in 1/2^20 second units) corresponding to tb_orig_stamp. This + new value of stamp_xsec compensates for the change in frequency (implied by the new tb_to_xs) + which guarantees that the current time remains the same */ + write_seqlock_irqsave( &xtime_lock, flags ); + tb_ticks = get_tb() - do_gtod.varp->tb_orig_stamp; + div128_by_32( 1024*1024, 0, new_tb_ticks_per_sec, &divres ); + new_tb_to_xs = divres.result_low; + new_xsec = mulhdu( tb_ticks, new_tb_to_xs ); + + old_xsec = mulhdu( tb_ticks, do_gtod.varp->tb_to_xs ); + new_stamp_xsec = do_gtod.varp->stamp_xsec + old_xsec - new_xsec; + + /* There are two copies of tb_to_xs and stamp_xsec so that no lock is needed to access and use these + values in do_gettimeofday. We alternate the copies and as long as a reasonable time elapses between + changes, there will never be inconsistent values. ntpd has a minimum of one minute between updates */ + + temp_idx = (do_gtod.var_idx == 0); + temp_varp = &do_gtod.vars[temp_idx]; + + temp_varp->tb_to_xs = new_tb_to_xs; + temp_varp->stamp_xsec = new_stamp_xsec; + temp_varp->tb_orig_stamp = do_gtod.varp->tb_orig_stamp; + mb(); + do_gtod.varp = temp_varp; + do_gtod.var_idx = temp_idx; + + /* + * tb_update_count is used to allow the problem state gettimeofday code + * to assure itself that it sees a consistent view of the tb_to_xs and + * stamp_xsec variables. It reads the tb_update_count, then reads + * tb_to_xs and stamp_xsec and then reads tb_update_count again. If + * 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. + */ + ++(systemcfg->tb_update_count); + wmb(); + systemcfg->tb_to_xs = new_tb_to_xs; + systemcfg->stamp_xsec = new_stamp_xsec; + wmb(); + ++(systemcfg->tb_update_count); + + write_sequnlock_irqrestore( &xtime_lock, flags ); + +} + + +#define TICK_SIZE tick +#define FEBRUARY 2 +#define STARTOFTIME 1970 +#define SECDAY 86400L +#define SECYR (SECDAY * 365) +#define leapyear(year) ((year) % 4 == 0) +#define days_in_year(a) (leapyear(a) ? 366 : 365) +#define days_in_month(a) (month_days[(a) - 1]) + +static int month_days[12] = { + 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 +}; + +/* + * This only works for the Gregorian calendar - i.e. after 1752 (in the UK) + */ +void GregorianDay(struct rtc_time * tm) +{ + int leapsToDate; + int lastYear; + int day; + int MonthOffset[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 }; + + lastYear=tm->tm_year-1; + + /* + * Number of leap corrections to apply up to end of last year + */ + leapsToDate = lastYear/4 - lastYear/100 + lastYear/400; + + /* + * This year is a leap year if it is divisible by 4 except when it is + * divisible by 100 unless it is divisible by 400 + * + * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 will be + */ + if((tm->tm_year%4==0) && + ((tm->tm_year%100!=0) || (tm->tm_year%400==0)) && + (tm->tm_mon>2)) + { + /* + * We are past Feb. 29 in a leap year + */ + day=1; + } + else + { + day=0; + } + + day += lastYear*365 + leapsToDate + MonthOffset[tm->tm_mon-1] + + tm->tm_mday; + + tm->tm_wday=day%7; +} + +void to_tm(int tim, struct rtc_time * tm) +{ + register int i; + register long hms, day; + + day = tim / SECDAY; + hms = tim % SECDAY; + + /* Hours, minutes, seconds are easy */ + tm->tm_hour = hms / 3600; + tm->tm_min = (hms % 3600) / 60; + tm->tm_sec = (hms % 3600) % 60; + + /* Number of years in days */ + for (i = STARTOFTIME; day >= days_in_year(i); i++) + day -= days_in_year(i); + tm->tm_year = i; + + /* Number of months in days left */ + if (leapyear(tm->tm_year)) + days_in_month(FEBRUARY) = 29; + for (i = 1; day >= days_in_month(i); i++) + day -= days_in_month(i); + days_in_month(FEBRUARY) = 28; + tm->tm_mon = i; + + /* Days are what is left over (+1) from all that. */ + tm->tm_mday = day + 1; + + /* + * Determine the day of week + */ + GregorianDay(tm); +} + +/* Auxiliary function to compute scaling factors */ +/* Actually the choice of a timebase running at 1/4 the of the bus + * frequency giving resolution of a few tens of nanoseconds is quite nice. + * It makes this computation very precise (27-28 bits typically) which + * is optimistic considering the stability of most processor clock + * oscillators and the precision with which the timebase frequency + * is measured but does not harm. + */ +unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) { + unsigned mlt=0, tmp, err; + /* No concern for performance, it's done once: use a stupid + * but safe and compact method to find the multiplier. + */ + + for (tmp = 1U<<31; tmp != 0; tmp >>= 1) { + if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp; + } + + /* We might still be off by 1 for the best approximation. + * A side effect of this is that if outscale is too large + * the returned value will be zero. + * Many corner cases have been checked and seem to work, + * some might have been forgotten in the test however. + */ + + err = inscale*(mlt+1); + if (err <= inscale/2) mlt++; + return mlt; + } + +/* + * Divide a 128-bit dividend by a 32-bit divisor, leaving a 128 bit + * result. + */ + +void div128_by_32( unsigned long dividend_high, unsigned long dividend_low, + unsigned divisor, struct div_result *dr ) +{ + unsigned long a,b,c,d, w,x,y,z, ra,rb,rc; + + a = dividend_high >> 32; + b = dividend_high & 0xffffffff; + c = dividend_low >> 32; + d = dividend_low & 0xffffffff; + + w = a/divisor; + ra = (a - (w * divisor)) << 32; + + x = (ra + b)/divisor; + rb = ((ra + b) - (x * divisor)) << 32; + + y = (rb + c)/divisor; + rc = ((rb + b) - (y * divisor)) << 32; + + z = (rc + d)/divisor; + + dr->result_high = (w << 32) + x; + dr->result_low = (y << 32) + z; + +} + |