/* * * 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); EXPORT_SYMBOL_GPL(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 int smp_tb_synchronized; extern struct timezone sys_tz; void ppc_adjtimex(void); static unsigned adjusting_time = 0; unsigned long ppc_proc_freq; unsigned long ppc_tb_freq; 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; smp_mb(); do_gtod.varp = temp_varp; do_gtod.var_idx = temp_idx; ++(systemcfg->tb_update_count); smp_wmb(); systemcfg->tb_orig_stamp = new_tb_orig_stamp; systemcfg->stamp_xsec = new_stamp_xsec; smp_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(); profile_tick(CPU_PROFILING, regs); 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 if (hvlpevent_is_pending()) process_hvlpevents(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); #if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_PPC_MAPLE) || defined(CONFIG_PPC_BPA) void __init generic_calibrate_decr(void) { struct device_node *cpu; struct div_result divres; unsigned int *fp; int node_found; /* * The cpu node should have a timebase-frequency property * to tell us the rate at which the decrementer counts. */ cpu = of_find_node_by_type(NULL, "cpu"); ppc_tb_freq = DEFAULT_TB_FREQ; /* hardcoded default */ node_found = 0; if (cpu != 0) { fp = (unsigned int *)get_property(cpu, "timebase-frequency", NULL); if (fp != 0) { node_found = 1; ppc_tb_freq = *fp; } } if (!node_found) printk(KERN_ERR "WARNING: Estimating decrementer frequency " "(not found)\n"); ppc_proc_freq = DEFAULT_PROC_FREQ; node_found = 0; if (cpu != 0) { fp = (unsigned int *)get_property(cpu, "clock-frequency", NULL); if (fp != 0) { node_found = 1; ppc_proc_freq = *fp; } } if (!node_found) printk(KERN_ERR "WARNING: Estimating processor frequency " "(not found)\n"); of_node_put(cpu); printk(KERN_INFO "time_init: decrementer frequency = %lu.%.6lu MHz\n", ppc_tb_freq/1000000, ppc_tb_freq%1000000); printk(KERN_INFO "time_init: processor frequency = %lu.%.6lu MHz\n", ppc_proc_freq/1000000, ppc_proc_freq%1000000); tb_ticks_per_jiffy = ppc_tb_freq / HZ; tb_ticks_per_sec = tb_ticks_per_jiffy * HZ; tb_ticks_per_usec = ppc_tb_freq / 1000000; tb_to_us = mulhwu_scale_factor(ppc_tb_freq, 1000000); div128_by_32(1024*1024, 0, tb_ticks_per_sec, &divres); tb_to_xs = divres.result_low; setup_default_decr(); } #endif 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; get_paca()->next_jiffy_update_tb = tb_last_stamp + tb_ticks_per_jiffy; 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; smp_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); smp_wmb(); systemcfg->tb_to_xs = new_tb_to_xs; systemcfg->stamp_xsec = new_stamp_xsec; smp_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; }