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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/ia64/kernel/time.c
downloadlinux-stericsson-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'arch/ia64/kernel/time.c')
-rw-r--r--arch/ia64/kernel/time.c255
1 files changed, 255 insertions, 0 deletions
diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
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+/*
+ * linux/arch/ia64/kernel/time.c
+ *
+ * Copyright (C) 1998-2003 Hewlett-Packard Co
+ * Stephane Eranian <eranian@hpl.hp.com>
+ * David Mosberger <davidm@hpl.hp.com>
+ * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
+ * Copyright (C) 1999-2000 VA Linux Systems
+ * Copyright (C) 1999-2000 Walt Drummond <drummond@valinux.com>
+ */
+#include <linux/config.h>
+
+#include <linux/cpu.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/profile.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+#include <linux/interrupt.h>
+#include <linux/efi.h>
+#include <linux/profile.h>
+#include <linux/timex.h>
+
+#include <asm/machvec.h>
+#include <asm/delay.h>
+#include <asm/hw_irq.h>
+#include <asm/ptrace.h>
+#include <asm/sal.h>
+#include <asm/sections.h>
+#include <asm/system.h>
+
+extern unsigned long wall_jiffies;
+
+u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
+
+EXPORT_SYMBOL(jiffies_64);
+
+#define TIME_KEEPER_ID 0 /* smp_processor_id() of time-keeper */
+
+#ifdef CONFIG_IA64_DEBUG_IRQ
+
+unsigned long last_cli_ip;
+EXPORT_SYMBOL(last_cli_ip);
+
+#endif
+
+static struct time_interpolator itc_interpolator = {
+ .shift = 16,
+ .mask = 0xffffffffffffffffLL,
+ .source = TIME_SOURCE_CPU
+};
+
+static irqreturn_t
+timer_interrupt (int irq, void *dev_id, struct pt_regs *regs)
+{
+ unsigned long new_itm;
+
+ if (unlikely(cpu_is_offline(smp_processor_id()))) {
+ return IRQ_HANDLED;
+ }
+
+ platform_timer_interrupt(irq, dev_id, regs);
+
+ new_itm = local_cpu_data->itm_next;
+
+ if (!time_after(ia64_get_itc(), new_itm))
+ printk(KERN_ERR "Oops: timer tick before it's due (itc=%lx,itm=%lx)\n",
+ ia64_get_itc(), new_itm);
+
+ profile_tick(CPU_PROFILING, regs);
+
+ while (1) {
+ update_process_times(user_mode(regs));
+
+ new_itm += local_cpu_data->itm_delta;
+
+ if (smp_processor_id() == TIME_KEEPER_ID) {
+ /*
+ * Here we are in the timer irq handler. We have irqs locally
+ * disabled, but we don't know if the timer_bh is running on
+ * another CPU. We need to avoid to SMP race by acquiring the
+ * xtime_lock.
+ */
+ write_seqlock(&xtime_lock);
+ do_timer(regs);
+ local_cpu_data->itm_next = new_itm;
+ write_sequnlock(&xtime_lock);
+ } else
+ local_cpu_data->itm_next = new_itm;
+
+ if (time_after(new_itm, ia64_get_itc()))
+ break;
+ }
+
+ do {
+ /*
+ * If we're too close to the next clock tick for
+ * comfort, we increase the safety margin by
+ * intentionally dropping the next tick(s). We do NOT
+ * update itm.next because that would force us to call
+ * do_timer() which in turn would let our clock run
+ * too fast (with the potentially devastating effect
+ * of losing monotony of time).
+ */
+ while (!time_after(new_itm, ia64_get_itc() + local_cpu_data->itm_delta/2))
+ new_itm += local_cpu_data->itm_delta;
+ ia64_set_itm(new_itm);
+ /* double check, in case we got hit by a (slow) PMI: */
+ } while (time_after_eq(ia64_get_itc(), new_itm));
+ return IRQ_HANDLED;
+}
+
+/*
+ * Encapsulate access to the itm structure for SMP.
+ */
+void
+ia64_cpu_local_tick (void)
+{
+ int cpu = smp_processor_id();
+ unsigned long shift = 0, delta;
+
+ /* arrange for the cycle counter to generate a timer interrupt: */
+ ia64_set_itv(IA64_TIMER_VECTOR);
+
+ delta = local_cpu_data->itm_delta;
+ /*
+ * Stagger the timer tick for each CPU so they don't occur all at (almost) the
+ * same time:
+ */
+ if (cpu) {
+ unsigned long hi = 1UL << ia64_fls(cpu);
+ shift = (2*(cpu - hi) + 1) * delta/hi/2;
+ }
+ local_cpu_data->itm_next = ia64_get_itc() + delta + shift;
+ ia64_set_itm(local_cpu_data->itm_next);
+}
+
+static int nojitter;
+
+static int __init nojitter_setup(char *str)
+{
+ nojitter = 1;
+ printk("Jitter checking for ITC timers disabled\n");
+ return 1;
+}
+
+__setup("nojitter", nojitter_setup);
+
+
+void __devinit
+ia64_init_itm (void)
+{
+ unsigned long platform_base_freq, itc_freq;
+ struct pal_freq_ratio itc_ratio, proc_ratio;
+ long status, platform_base_drift, itc_drift;
+
+ /*
+ * According to SAL v2.6, we need to use a SAL call to determine the platform base
+ * frequency and then a PAL call to determine the frequency ratio between the ITC
+ * and the base frequency.
+ */
+ status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
+ &platform_base_freq, &platform_base_drift);
+ if (status != 0) {
+ printk(KERN_ERR "SAL_FREQ_BASE_PLATFORM failed: %s\n", ia64_sal_strerror(status));
+ } else {
+ status = ia64_pal_freq_ratios(&proc_ratio, NULL, &itc_ratio);
+ if (status != 0)
+ printk(KERN_ERR "PAL_FREQ_RATIOS failed with status=%ld\n", status);
+ }
+ if (status != 0) {
+ /* invent "random" values */
+ printk(KERN_ERR
+ "SAL/PAL failed to obtain frequency info---inventing reasonable values\n");
+ platform_base_freq = 100000000;
+ platform_base_drift = -1; /* no drift info */
+ itc_ratio.num = 3;
+ itc_ratio.den = 1;
+ }
+ if (platform_base_freq < 40000000) {
+ printk(KERN_ERR "Platform base frequency %lu bogus---resetting to 75MHz!\n",
+ platform_base_freq);
+ platform_base_freq = 75000000;
+ platform_base_drift = -1;
+ }
+ if (!proc_ratio.den)
+ proc_ratio.den = 1; /* avoid division by zero */
+ if (!itc_ratio.den)
+ itc_ratio.den = 1; /* avoid division by zero */
+
+ itc_freq = (platform_base_freq*itc_ratio.num)/itc_ratio.den;
+
+ local_cpu_data->itm_delta = (itc_freq + HZ/2) / HZ;
+ printk(KERN_DEBUG "CPU %d: base freq=%lu.%03luMHz, ITC ratio=%lu/%lu, "
+ "ITC freq=%lu.%03luMHz", smp_processor_id(),
+ platform_base_freq / 1000000, (platform_base_freq / 1000) % 1000,
+ itc_ratio.num, itc_ratio.den, itc_freq / 1000000, (itc_freq / 1000) % 1000);
+
+ if (platform_base_drift != -1) {
+ itc_drift = platform_base_drift*itc_ratio.num/itc_ratio.den;
+ printk("+/-%ldppm\n", itc_drift);
+ } else {
+ itc_drift = -1;
+ printk("\n");
+ }
+
+ local_cpu_data->proc_freq = (platform_base_freq*proc_ratio.num)/proc_ratio.den;
+ local_cpu_data->itc_freq = itc_freq;
+ local_cpu_data->cyc_per_usec = (itc_freq + USEC_PER_SEC/2) / USEC_PER_SEC;
+ local_cpu_data->nsec_per_cyc = ((NSEC_PER_SEC<<IA64_NSEC_PER_CYC_SHIFT)
+ + itc_freq/2)/itc_freq;
+
+ if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
+ itc_interpolator.frequency = local_cpu_data->itc_freq;
+ itc_interpolator.drift = itc_drift;
+#ifdef CONFIG_SMP
+ /* On IA64 in an SMP configuration ITCs are never accurately synchronized.
+ * Jitter compensation requires a cmpxchg which may limit
+ * the scalability of the syscalls for retrieving time.
+ * The ITC synchronization is usually successful to within a few
+ * ITC ticks but this is not a sure thing. If you need to improve
+ * timer performance in SMP situations then boot the kernel with the
+ * "nojitter" option. However, doing so may result in time fluctuating (maybe
+ * even going backward) if the ITC offsets between the individual CPUs
+ * are too large.
+ */
+ if (!nojitter) itc_interpolator.jitter = 1;
+#endif
+ register_time_interpolator(&itc_interpolator);
+ }
+
+ /* Setup the CPU local timer tick */
+ ia64_cpu_local_tick();
+}
+
+static struct irqaction timer_irqaction = {
+ .handler = timer_interrupt,
+ .flags = SA_INTERRUPT,
+ .name = "timer"
+};
+
+void __init
+time_init (void)
+{
+ register_percpu_irq(IA64_TIMER_VECTOR, &timer_irqaction);
+ efi_gettimeofday(&xtime);
+ ia64_init_itm();
+
+ /*
+ * Initialize wall_to_monotonic such that adding it to xtime will yield zero, the
+ * tv_nsec field must be normalized (i.e., 0 <= nsec < NSEC_PER_SEC).
+ */
+ set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
+}