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 000000000000..77ded5a363b6
--- /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;
+
+}
+