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Diffstat (limited to 'arch/ppc/kernel/time.c')
| -rw-r--r-- | arch/ppc/kernel/time.c | 447 |
1 files changed, 447 insertions, 0 deletions
diff --git a/arch/ppc/kernel/time.c b/arch/ppc/kernel/time.c new file mode 100644 index 00000000000..50724139402 --- /dev/null +++ b/arch/ppc/kernel/time.c @@ -0,0 +1,447 @@ +/* + * 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). + * + * 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). + * + * TODO (not necessarily in this file): + * - improve precision and reproducibility of timebase frequency + * measurement at boot time. + * - get rid of xtime_lock for gettimeofday (generic kernel problem + * to be implemented on all architectures for SMP scalability and + * eventually implementing gettimeofday without entering the kernel). + * - put all time/clock related variables in a single structure + * to minimize number of cache lines touched by gettimeofday() + * - 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. + * + * + * The following comment is partially obsolete (at least the long wait + * is no more a valid reason): + * Since the MPC8xx has a programmable interrupt timer, I decided to + * use that rather than the decrementer. Two reasons: 1.) the clock + * frequency is low, causing 2.) a long wait in the timer interrupt + * while ((d = get_dec()) == dval) + * loop. The MPC8xx can be driven from a variety of input clocks, + * so a number of assumptions have been made here because the kernel + * parameter HZ is a constant. We assume (correctly, today :-) that + * the MPC8xx on the MBX board is driven from a 32.768 kHz crystal. + * This is then divided by 4, providing a 8192 Hz clock into the PIT. + * Since it is not possible to get a nice 100 Hz clock out of this, without + * creating a software PLL, I have set HZ to 128. -- Dan + * + * 1997-09-10 Updated NTP code according to technical memorandum Jan '96 + * "A Kernel Model for Precision Timekeeping" by Dave Mills + */ + +#include <linux/config.h> +#include <linux/errno.h> +#include <linux/sched.h> +#include <linux/kernel.h> +#include <linux/param.h> +#include <linux/string.h> +#include <linux/mm.h> +#include <linux/module.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 <asm/segment.h> +#include <asm/io.h> +#include <asm/nvram.h> +#include <asm/cache.h> +#include <asm/8xx_immap.h> +#include <asm/machdep.h> + +#include <asm/time.h> + +/* XXX false sharing with below? */ +u64 jiffies_64 = INITIAL_JIFFIES; + +EXPORT_SYMBOL(jiffies_64); + +unsigned long disarm_decr[NR_CPUS]; + +extern struct timezone sys_tz; + +/* keep track of when we need to update the rtc */ +time_t last_rtc_update; + +/* The decrementer counts down by 128 every 128ns on a 601. */ +#define DECREMENTER_COUNT_601 (1000000000 / HZ) + +unsigned tb_ticks_per_jiffy; +unsigned tb_to_us; +unsigned tb_last_stamp; +unsigned long tb_to_ns_scale; + +extern unsigned long wall_jiffies; + +static long time_offset; + +DEFINE_SPINLOCK(rtc_lock); + +EXPORT_SYMBOL(rtc_lock); + +/* Timer interrupt helper function */ +static inline int tb_delta(unsigned *jiffy_stamp) { + int delta; + if (__USE_RTC()) { + delta = get_rtcl(); + if (delta < *jiffy_stamp) *jiffy_stamp -= 1000000000; + delta -= *jiffy_stamp; + } else { + delta = get_tbl() - *jiffy_stamp; + } + return delta; +} + +#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 + +/* + * timer_interrupt - gets called when the decrementer overflows, + * with interrupts disabled. + * We set it up to overflow again in 1/HZ seconds. + */ +void timer_interrupt(struct pt_regs * regs) +{ + int next_dec; + unsigned long cpu = smp_processor_id(); + unsigned jiffy_stamp = last_jiffy_stamp(cpu); + extern void do_IRQ(struct pt_regs *); + + if (atomic_read(&ppc_n_lost_interrupts) != 0) + do_IRQ(regs); + + irq_enter(); + + while ((next_dec = tb_ticks_per_jiffy - tb_delta(&jiffy_stamp)) <= 0) { + jiffy_stamp += tb_ticks_per_jiffy; + + profile_tick(CPU_PROFILING, regs); + update_process_times(user_mode(regs)); + + if (smp_processor_id()) + continue; + + /* We are in an interrupt, no need to save/restore flags */ + write_seqlock(&xtime_lock); + tb_last_stamp = jiffy_stamp; + do_timer(regs); + + /* + * 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 ( ppc_md.set_rtc_time && (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) { + if (ppc_md.set_rtc_time(xtime.tv_sec+1 + time_offset) == 0) + last_rtc_update = xtime.tv_sec+1; + else + /* Try again one minute later */ + last_rtc_update += 60; + } + write_sequnlock(&xtime_lock); + } + if ( !disarm_decr[smp_processor_id()] ) + set_dec(next_dec); + last_jiffy_stamp(cpu) = jiffy_stamp; + + if (ppc_md.heartbeat && !ppc_md.heartbeat_count--) + ppc_md.heartbeat(); + + irq_exit(); +} + +/* + * This version of gettimeofday has microsecond resolution. + */ +void do_gettimeofday(struct timeval *tv) +{ + unsigned long flags; + unsigned long seq; + unsigned delta, lost_ticks, usec, sec; + + do { + seq = read_seqbegin_irqsave(&xtime_lock, flags); + sec = xtime.tv_sec; + usec = (xtime.tv_nsec / 1000); + delta = tb_ticks_since(tb_last_stamp); +#ifdef CONFIG_SMP + /* As long as timebases are not in sync, gettimeofday can only + * have jiffy resolution on SMP. + */ + if (!smp_tb_synchronized) + delta = 0; +#endif /* CONFIG_SMP */ + lost_ticks = jiffies - wall_jiffies; + } while (read_seqretry_irqrestore(&xtime_lock, seq, flags)); + + usec += mulhwu(tb_to_us, tb_ticks_per_jiffy * lost_ticks + delta); + while (usec >= 1000000) { + sec++; + usec -= 1000000; + } + tv->tv_sec = sec; + tv->tv_usec = usec; +} + +EXPORT_SYMBOL(do_gettimeofday); + +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; + int tb_delta; + + 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. Note also that + * we don't touch the decrementer since: + * a) it would lose timer interrupt synchronization on SMP + * (if it is working one day) + * b) it could make one jiffy spuriously shorter or longer + * which would introduce another source of uncertainty potentially + * harmful to relatively short timers. + */ + + /* This works perfectly on SMP only if the tb are in sync but + * guarantees an error < 1 jiffy even if they are off by eons, + * still reasonable when gettimeofday resolution is 1 jiffy. + */ + tb_delta = tb_ticks_since(last_jiffy_stamp(smp_processor_id())); + tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy; + + new_nsec -= 1000 * mulhwu(tb_to_us, tb_delta); + + 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_state = TIME_ERROR; /* p. 24, (a) */ + time_maxerror = NTP_PHASE_LIMIT; + time_esterror = NTP_PHASE_LIMIT; + write_sequnlock_irqrestore(&xtime_lock, flags); + clock_was_set(); + return 0; +} + +EXPORT_SYMBOL(do_settimeofday); + +/* This function is only called on the boot processor */ +void __init time_init(void) +{ + time_t sec, old_sec; + unsigned old_stamp, stamp, elapsed; + + if (ppc_md.time_init != NULL) + time_offset = ppc_md.time_init(); + + if (__USE_RTC()) { + /* 601 processor: dec counts down by 128 every 128ns */ + tb_ticks_per_jiffy = DECREMENTER_COUNT_601; + /* mulhwu_scale_factor(1000000000, 1000000) is 0x418937 */ + tb_to_us = 0x418937; + } else { + ppc_md.calibrate_decr(); + tb_to_ns_scale = mulhwu(tb_to_us, 1000 << 10); + } + + /* Now that the decrementer is calibrated, it can be used in case the + * clock is stuck, but the fact that we have to handle the 601 + * makes things more complex. Repeatedly read the RTC until the + * next second boundary to try to achieve some precision. If there + * is no RTC, we still need to set tb_last_stamp and + * last_jiffy_stamp(cpu 0) to the current stamp. + */ + stamp = get_native_tbl(); + if (ppc_md.get_rtc_time) { + sec = ppc_md.get_rtc_time(); + elapsed = 0; + do { + old_stamp = stamp; + old_sec = sec; + stamp = get_native_tbl(); + if (__USE_RTC() && stamp < old_stamp) + old_stamp -= 1000000000; + elapsed += stamp - old_stamp; + sec = ppc_md.get_rtc_time(); + } while ( sec == old_sec && elapsed < 2*HZ*tb_ticks_per_jiffy); + if (sec==old_sec) + printk("Warning: real time clock seems stuck!\n"); + xtime.tv_sec = sec; + xtime.tv_nsec = 0; + /* No update now, we just read the time from the RTC ! */ + last_rtc_update = xtime.tv_sec; + } + last_jiffy_stamp(0) = tb_last_stamp = stamp; + + /* Not exact, but the timer interrupt takes care of this */ + set_dec(tb_ticks_per_jiffy); + + /* If platform provided a timezone (pmac), we correct the time */ + if (time_offset) { + sys_tz.tz_minuteswest = -time_offset / 60; + sys_tz.tz_dsttime = 0; + xtime.tv_sec -= time_offset; + } + set_normalized_timespec(&wall_to_monotonic, + -xtime.tv_sec, -xtime.tv_nsec); +} + +#define FEBRUARY 2 +#define STARTOFTIME 1970 +#define SECDAY 86400L +#define SECYR (SECDAY * 365) + +/* + * Note: this is wrong for 2100, but our signed 32-bit time_t will + * have overflowed long before that, so who cares. -- paulus + */ +#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 +}; + +void to_tm(int tim, struct rtc_time * tm) +{ + register int i; + register long hms, day, gday; + + gday = 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. Jan. 1, 1970 was a Thursday. + */ + tm->tm_wday = (gday + 4) % 7; +} + +/* 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; +} + +unsigned long long sched_clock(void) +{ + unsigned long lo, hi, hi2; + unsigned long long tb; + + if (!__USE_RTC()) { + do { + hi = get_tbu(); + lo = get_tbl(); + hi2 = get_tbu(); + } while (hi2 != hi); + tb = ((unsigned long long) hi << 32) | lo; + tb = (tb * tb_to_ns_scale) >> 10; + } else { + do { + hi = get_rtcu(); + lo = get_rtcl(); + hi2 = get_rtcu(); + } while (hi2 != hi); + tb = ((unsigned long long) hi) * 1000000000 + lo; + } + return tb; +} |