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446 lines
13 KiB
446 lines
13 KiB
/*
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* Common time routines among all ppc machines.
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*
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* Written by Cort Dougan (cort@cs.nmt.edu) to merge
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* Paul Mackerras' version and mine for PReP and Pmac.
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* MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net).
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*
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* First round of bugfixes by Gabriel Paubert (paubert@iram.es)
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* to make clock more stable (2.4.0-test5). The only thing
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* that this code assumes is that the timebases have been synchronized
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* by firmware on SMP and are never stopped (never do sleep
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* on SMP then, nap and doze are OK).
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*
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* TODO (not necessarily in this file):
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* - improve precision and reproducibility of timebase frequency
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* measurement at boot time.
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* - get rid of xtime_lock for gettimeofday (generic kernel problem
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* to be implemented on all architectures for SMP scalability and
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* eventually implementing gettimeofday without entering the kernel).
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* - put all time/clock related variables in a single structure
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* to minimize number of cache lines touched by gettimeofday()
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* - for astronomical applications: add a new function to get
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* non ambiguous timestamps even around leap seconds. This needs
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* a new timestamp format and a good name.
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*
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*
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* The following comment is partially obsolete (at least the long wait
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* is no more a valid reason):
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* Since the MPC8xx has a programmable interrupt timer, I decided to
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* use that rather than the decrementer. Two reasons: 1.) the clock
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* frequency is low, causing 2.) a long wait in the timer interrupt
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* while ((d = get_dec()) == dval)
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* loop. The MPC8xx can be driven from a variety of input clocks,
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* so a number of assumptions have been made here because the kernel
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* parameter HZ is a constant. We assume (correctly, today :-) that
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* the MPC8xx on the MBX board is driven from a 32.768 kHz crystal.
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* This is then divided by 4, providing a 8192 Hz clock into the PIT.
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* Since it is not possible to get a nice 100 Hz clock out of this, without
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* creating a software PLL, I have set HZ to 128. -- Dan
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*
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* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
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* "A Kernel Model for Precision Timekeeping" by Dave Mills
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*/
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/param.h>
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#include <linux/string.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/interrupt.h>
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#include <linux/timex.h>
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#include <linux/kernel_stat.h>
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#include <linux/mc146818rtc.h>
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#include <linux/time.h>
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#include <linux/init.h>
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#include <linux/profile.h>
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#include <asm/io.h>
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#include <asm/nvram.h>
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#include <asm/cache.h>
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#include <asm/8xx_immap.h>
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#include <asm/machdep.h>
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#include <asm/time.h>
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unsigned long disarm_decr[NR_CPUS];
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extern struct timezone sys_tz;
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/* keep track of when we need to update the rtc */
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time_t last_rtc_update;
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/* The decrementer counts down by 128 every 128ns on a 601. */
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#define DECREMENTER_COUNT_601 (1000000000 / HZ)
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unsigned tb_ticks_per_jiffy;
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unsigned tb_to_us;
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unsigned tb_last_stamp;
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unsigned long tb_to_ns_scale;
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extern unsigned long wall_jiffies;
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/* used for timezone offset */
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static long timezone_offset;
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DEFINE_SPINLOCK(rtc_lock);
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EXPORT_SYMBOL(rtc_lock);
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/* Timer interrupt helper function */
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static inline int tb_delta(unsigned *jiffy_stamp) {
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int delta;
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if (__USE_RTC()) {
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delta = get_rtcl();
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if (delta < *jiffy_stamp) *jiffy_stamp -= 1000000000;
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delta -= *jiffy_stamp;
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} else {
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delta = get_tbl() - *jiffy_stamp;
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}
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return delta;
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}
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#ifdef CONFIG_SMP
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unsigned long profile_pc(struct pt_regs *regs)
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{
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unsigned long pc = instruction_pointer(regs);
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if (in_lock_functions(pc))
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return regs->link;
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return pc;
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}
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EXPORT_SYMBOL(profile_pc);
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#endif
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void wakeup_decrementer(void)
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{
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set_dec(tb_ticks_per_jiffy);
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/* No currently-supported powerbook has a 601,
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* so use get_tbl, not native
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*/
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last_jiffy_stamp(0) = tb_last_stamp = get_tbl();
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}
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/*
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* timer_interrupt - gets called when the decrementer overflows,
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* with interrupts disabled.
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* We set it up to overflow again in 1/HZ seconds.
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*/
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void timer_interrupt(struct pt_regs * regs)
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{
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int next_dec;
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unsigned long cpu = smp_processor_id();
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unsigned jiffy_stamp = last_jiffy_stamp(cpu);
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extern void do_IRQ(struct pt_regs *);
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if (atomic_read(&ppc_n_lost_interrupts) != 0)
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do_IRQ(regs);
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irq_enter();
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while ((next_dec = tb_ticks_per_jiffy - tb_delta(&jiffy_stamp)) <= 0) {
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jiffy_stamp += tb_ticks_per_jiffy;
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profile_tick(CPU_PROFILING, regs);
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update_process_times(user_mode(regs));
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if (smp_processor_id())
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continue;
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/* We are in an interrupt, no need to save/restore flags */
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write_seqlock(&xtime_lock);
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tb_last_stamp = jiffy_stamp;
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do_timer(regs);
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/*
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* update the rtc when needed, this should be performed on the
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* right fraction of a second. Half or full second ?
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* Full second works on mk48t59 clocks, others need testing.
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* Note that this update is basically only used through
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* the adjtimex system calls. Setting the HW clock in
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* any other way is a /dev/rtc and userland business.
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* This is still wrong by -0.5/+1.5 jiffies because of the
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* timer interrupt resolution and possible delay, but here we
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* hit a quantization limit which can only be solved by higher
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* resolution timers and decoupling time management from timer
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* interrupts. This is also wrong on the clocks
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* which require being written at the half second boundary.
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* We should have an rtc call that only sets the minutes and
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* seconds like on Intel to avoid problems with non UTC clocks.
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*/
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if ( ppc_md.set_rtc_time && ntp_synced() &&
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xtime.tv_sec - last_rtc_update >= 659 &&
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abs((xtime.tv_nsec / 1000) - (1000000-1000000/HZ)) < 500000/HZ &&
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jiffies - wall_jiffies == 1) {
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if (ppc_md.set_rtc_time(xtime.tv_sec+1 + timezone_offset) == 0)
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last_rtc_update = xtime.tv_sec+1;
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else
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/* Try again one minute later */
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last_rtc_update += 60;
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}
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write_sequnlock(&xtime_lock);
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}
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if ( !disarm_decr[smp_processor_id()] )
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set_dec(next_dec);
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last_jiffy_stamp(cpu) = jiffy_stamp;
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if (ppc_md.heartbeat && !ppc_md.heartbeat_count--)
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ppc_md.heartbeat();
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irq_exit();
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}
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/*
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* This version of gettimeofday has microsecond resolution.
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*/
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void do_gettimeofday(struct timeval *tv)
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{
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unsigned long flags;
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unsigned long seq;
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unsigned delta, lost_ticks, usec, sec;
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do {
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seq = read_seqbegin_irqsave(&xtime_lock, flags);
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sec = xtime.tv_sec;
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usec = (xtime.tv_nsec / 1000);
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delta = tb_ticks_since(tb_last_stamp);
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#ifdef CONFIG_SMP
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/* As long as timebases are not in sync, gettimeofday can only
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* have jiffy resolution on SMP.
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*/
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if (!smp_tb_synchronized)
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delta = 0;
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#endif /* CONFIG_SMP */
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lost_ticks = jiffies - wall_jiffies;
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} while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
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usec += mulhwu(tb_to_us, tb_ticks_per_jiffy * lost_ticks + delta);
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while (usec >= 1000000) {
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sec++;
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usec -= 1000000;
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}
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tv->tv_sec = sec;
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tv->tv_usec = usec;
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}
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EXPORT_SYMBOL(do_gettimeofday);
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int do_settimeofday(struct timespec *tv)
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{
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time_t wtm_sec, new_sec = tv->tv_sec;
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long wtm_nsec, new_nsec = tv->tv_nsec;
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unsigned long flags;
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int tb_delta;
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if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
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return -EINVAL;
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write_seqlock_irqsave(&xtime_lock, flags);
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/* Updating the RTC is not the job of this code. If the time is
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* stepped under NTP, the RTC will be update after STA_UNSYNC
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* is cleared. Tool like clock/hwclock either copy the RTC
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* to the system time, in which case there is no point in writing
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* to the RTC again, or write to the RTC but then they don't call
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* settimeofday to perform this operation. Note also that
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* we don't touch the decrementer since:
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* a) it would lose timer interrupt synchronization on SMP
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* (if it is working one day)
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* b) it could make one jiffy spuriously shorter or longer
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* which would introduce another source of uncertainty potentially
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* harmful to relatively short timers.
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*/
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/* This works perfectly on SMP only if the tb are in sync but
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* guarantees an error < 1 jiffy even if they are off by eons,
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* still reasonable when gettimeofday resolution is 1 jiffy.
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*/
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tb_delta = tb_ticks_since(last_jiffy_stamp(smp_processor_id()));
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tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy;
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new_nsec -= 1000 * mulhwu(tb_to_us, tb_delta);
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wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - new_sec);
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wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - new_nsec);
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set_normalized_timespec(&xtime, new_sec, new_nsec);
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set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
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/* In case of a large backwards jump in time with NTP, we want the
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* clock to be updated as soon as the PLL is again in lock.
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*/
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last_rtc_update = new_sec - 658;
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ntp_clear();
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write_sequnlock_irqrestore(&xtime_lock, flags);
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clock_was_set();
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return 0;
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}
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EXPORT_SYMBOL(do_settimeofday);
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/* This function is only called on the boot processor */
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void __init time_init(void)
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{
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time_t sec, old_sec;
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unsigned old_stamp, stamp, elapsed;
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if (ppc_md.time_init != NULL)
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timezone_offset = ppc_md.time_init();
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if (__USE_RTC()) {
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/* 601 processor: dec counts down by 128 every 128ns */
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tb_ticks_per_jiffy = DECREMENTER_COUNT_601;
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/* mulhwu_scale_factor(1000000000, 1000000) is 0x418937 */
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tb_to_us = 0x418937;
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} else {
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ppc_md.calibrate_decr();
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tb_to_ns_scale = mulhwu(tb_to_us, 1000 << 10);
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}
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/* Now that the decrementer is calibrated, it can be used in case the
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* clock is stuck, but the fact that we have to handle the 601
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* makes things more complex. Repeatedly read the RTC until the
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* next second boundary to try to achieve some precision. If there
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* is no RTC, we still need to set tb_last_stamp and
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* last_jiffy_stamp(cpu 0) to the current stamp.
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*/
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stamp = get_native_tbl();
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if (ppc_md.get_rtc_time) {
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sec = ppc_md.get_rtc_time();
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elapsed = 0;
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do {
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old_stamp = stamp;
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old_sec = sec;
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stamp = get_native_tbl();
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if (__USE_RTC() && stamp < old_stamp)
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old_stamp -= 1000000000;
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elapsed += stamp - old_stamp;
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sec = ppc_md.get_rtc_time();
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} while ( sec == old_sec && elapsed < 2*HZ*tb_ticks_per_jiffy);
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if (sec==old_sec)
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printk("Warning: real time clock seems stuck!\n");
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xtime.tv_sec = sec;
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xtime.tv_nsec = 0;
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/* No update now, we just read the time from the RTC ! */
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last_rtc_update = xtime.tv_sec;
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}
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last_jiffy_stamp(0) = tb_last_stamp = stamp;
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/* Not exact, but the timer interrupt takes care of this */
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set_dec(tb_ticks_per_jiffy);
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/* If platform provided a timezone (pmac), we correct the time */
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if (timezone_offset) {
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sys_tz.tz_minuteswest = -timezone_offset / 60;
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sys_tz.tz_dsttime = 0;
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xtime.tv_sec -= timezone_offset;
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}
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set_normalized_timespec(&wall_to_monotonic,
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-xtime.tv_sec, -xtime.tv_nsec);
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}
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#define FEBRUARY 2
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#define STARTOFTIME 1970
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#define SECDAY 86400L
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#define SECYR (SECDAY * 365)
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/*
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* Note: this is wrong for 2100, but our signed 32-bit time_t will
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* have overflowed long before that, so who cares. -- paulus
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*/
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#define leapyear(year) ((year) % 4 == 0)
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#define days_in_year(a) (leapyear(a) ? 366 : 365)
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#define days_in_month(a) (month_days[(a) - 1])
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static int month_days[12] = {
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31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
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};
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void to_tm(int tim, struct rtc_time * tm)
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{
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register int i;
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register long hms, day, gday;
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gday = day = tim / SECDAY;
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hms = tim % SECDAY;
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/* Hours, minutes, seconds are easy */
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tm->tm_hour = hms / 3600;
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tm->tm_min = (hms % 3600) / 60;
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tm->tm_sec = (hms % 3600) % 60;
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/* Number of years in days */
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for (i = STARTOFTIME; day >= days_in_year(i); i++)
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day -= days_in_year(i);
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tm->tm_year = i;
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/* Number of months in days left */
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if (leapyear(tm->tm_year))
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days_in_month(FEBRUARY) = 29;
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for (i = 1; day >= days_in_month(i); i++)
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day -= days_in_month(i);
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days_in_month(FEBRUARY) = 28;
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tm->tm_mon = i;
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/* Days are what is left over (+1) from all that. */
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tm->tm_mday = day + 1;
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/*
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* Determine the day of week. Jan. 1, 1970 was a Thursday.
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*/
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tm->tm_wday = (gday + 4) % 7;
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}
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/* Auxiliary function to compute scaling factors */
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/* Actually the choice of a timebase running at 1/4 the of the bus
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* frequency giving resolution of a few tens of nanoseconds is quite nice.
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* It makes this computation very precise (27-28 bits typically) which
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* is optimistic considering the stability of most processor clock
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* oscillators and the precision with which the timebase frequency
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* is measured but does not harm.
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*/
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unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) {
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unsigned mlt=0, tmp, err;
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/* No concern for performance, it's done once: use a stupid
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* but safe and compact method to find the multiplier.
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*/
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for (tmp = 1U<<31; tmp != 0; tmp >>= 1) {
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if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp;
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}
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/* We might still be off by 1 for the best approximation.
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* A side effect of this is that if outscale is too large
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* the returned value will be zero.
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* Many corner cases have been checked and seem to work,
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* some might have been forgotten in the test however.
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*/
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err = inscale*(mlt+1);
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if (err <= inscale/2) mlt++;
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return mlt;
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}
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unsigned long long sched_clock(void)
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{
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unsigned long lo, hi, hi2;
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unsigned long long tb;
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if (!__USE_RTC()) {
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do {
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hi = get_tbu();
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lo = get_tbl();
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hi2 = get_tbu();
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} while (hi2 != hi);
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tb = ((unsigned long long) hi << 32) | lo;
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tb = (tb * tb_to_ns_scale) >> 10;
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} else {
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do {
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hi = get_rtcu();
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lo = get_rtcl();
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hi2 = get_rtcu();
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} while (hi2 != hi);
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tb = ((unsigned long long) hi) * 1000000000 + lo;
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}
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return tb;
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}
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