[PATCH 16/18] x86: apic copy calibrate_APIC_clock to each other in apic_32/64.c

Yinghai Lu
2008-08-24T09:08:45Z

arch/x86/kernel/apic_32.c | 86 ++++++++++++++++++
arch/x86/kernel/apic_64.c | 215 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 301 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/apic_32.c b/arch/x86/kernel/apic_32.c
index d357038..b21b772 100644
--- a/arch/x86/kernel/apic_32.c
+++ b/arch/x86/kernel/apic_32.c
@@ -424,6 +424,90 @@ static void __cpuinit setup_APIC_timer(void)
clockevents_register_device(levt);
}

+#ifdef CONFIG_X86_64
+/*
+ * In this function we calibrate APIC bus clocks to the external
+ * timer. Unfortunately we cannot use jiffies and the timer irq
+ * to calibrate, since some later bootup code depends on getting
+ * the first irq? Ugh.
+ *
+ * We want to do the calibration only once since we
+ * want to have local timer irqs syncron. CPUs connected
+ * by the same APIC bus have the very same bus frequency.
+ * And we want to have irqs off anyways, no accidental
+ * APIC irq that way.
+ */
+
+#define TICK_COUNT 100000000
+
+static int __init calibrate_APIC_clock(void)
+{
+ unsigned apic, apic_start;
+ unsigned long tsc, tsc_start;
+ int result;
+
+ local_irq_disable();
+
+ /*
+ * Put whatever arbitrary (but long enough) timeout
+ * value into the APIC clock, we just want to get the
+ * counter running for calibration.
+ *
+ * No interrupt enable !
+ */
+ __setup_APIC_LVTT(250000000, 0, 0);
+
+ apic_start = apic_read(APIC_TMCCT);
+#ifdef CONFIG_X86_PM_TIMER
+ if (apic_calibrate_pmtmr && pmtmr_ioport) {
+ pmtimer_wait(5000); /* 5ms wait */
+ apic = apic_read(APIC_TMCCT);
+ result = (apic_start - apic) * 1000L / 5;
+ } else
+#endif
+ {
+ rdtscll(tsc_start);
+
+ do {
+ apic = apic_read(APIC_TMCCT);
+ rdtscll(tsc);
+ } while ((tsc - tsc_start) < TICK_COUNT &&
+ (apic_start - apic) < TICK_COUNT);
+
+ result = (apic_start - apic) * 1000L * tsc_khz /
+ (tsc - tsc_start);
+ }
+
+ local_irq_enable();
+
+ printk(KERN_DEBUG "APIC timer calibration result %d\n", result);
+
+ printk(KERN_INFO "Detected %d.%03d MHz APIC timer.\n",
+ result / 1000 / 1000, result / 1000 % 1000);
+
+ /* Calculate the scaled math multiplication factor */
+ lapic_clockevent.mult = div_sc(result, NSEC_PER_SEC,
+ lapic_clockevent.shift);
+ lapic_clockevent.max_delta_ns =
+ clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);
+ lapic_clockevent.min_delta_ns =
+ clockevent_delta2ns(0xF, &lapic_clockevent);
+
+ calibration_result = (result * APIC_DIVISOR) / HZ;
+
+ /*
+ * Do a sanity check on the APIC calibration result
+ */
+ if (calibration_result < (1000000 / HZ)) {
+ printk(KERN_WARNING
+ "APIC frequency too slow, disabling apic timer\n");
+ return -1;
+ }
+
+ return 0;
+}
+
+#else
/*
* In this functions we calibrate APIC bus clocks to the external timer.
*
@@ -635,6 +719,8 @@ static int __init calibrate_APIC_clock(void)
return 0;
}

+#endif
+
/*
* Setup the boot APIC
*
diff --git a/arch/x86/kernel/apic_64.c b/arch/x86/kernel/apic_64.c
index c728885..6e99af5 100644
--- a/arch/x86/kernel/apic_64.c
+++ b/arch/x86/kernel/apic_64.c
@@ -478,6 +478,7 @@ static void __cpuinit setup_APIC_timer(void)
clockevents_register_device(levt);
}

+#ifdef CONFIG_X86_64
/*
* In this function we calibrate APIC bus clocks to the external
* timer. Unfortunately we cannot use jiffies and the timer irq
@@ -560,6 +561,220 @@ static int __init calibrate_APIC_clock(void)
return 0;
}

+#else
+/*
+ * In this functions we calibrate APIC bus clocks to the external timer.
+ *
+ * We want to do the calibration only once since we want to have local timer
+ * irqs syncron. CPUs connected by the same APIC bus have the very same bus
+ * frequency.
+ *
+ * This was previously done by reading the PIT/HPET and waiting for a wrap
+ * around to find out, that a tick has elapsed. I have a box, where the PIT
+ * readout is broken, so it never gets out of the wait loop again. This was
+ * also reported by others.
+ *
+ * Monitoring the jiffies value is inaccurate and the clockevents
+ * infrastructure allows us to do a simple substitution of the interrupt
+ * handler.
+ *
+ * The calibration routine also uses the pm_timer when possible, as the PIT
+ * happens to run way too slow (factor 2.3 on my VAIO CoreDuo, which goes
+ * back to normal later in the boot process).
+ */
+
+#define LAPIC_CAL_LOOPS (HZ/10)
+
+static __initdata int lapic_cal_loops = -1;
+static __initdata long lapic_cal_t1, lapic_cal_t2;
+static __initdata unsigned long long lapic_cal_tsc1, lapic_cal_tsc2;
+static __initdata unsigned long lapic_cal_pm1, lapic_cal_pm2;
+static __initdata unsigned long lapic_cal_j1, lapic_cal_j2;
+
+/*
+ * Temporary interrupt handler.
+ */
+static void __init lapic_cal_handler(struct clock_event_device *dev)
+{
+ unsigned long long tsc = 0;
+ long tapic = apic_read(APIC_TMCCT);
+ unsigned long pm = acpi_pm_read_early();
+
+ if (cpu_has_tsc)
+ rdtscll(tsc);
+
+ switch (lapic_cal_loops++) {
+ case 0:
+ lapic_cal_t1 = tapic;
+ lapic_cal_tsc1 = tsc;
+ lapic_cal_pm1 = pm;
+ lapic_cal_j1 = jiffies;
+ break;
+
+ case LAPIC_CAL_LOOPS:
+ lapic_cal_t2 = tapic;
+ lapic_cal_tsc2 = tsc;
+ if (pm < lapic_cal_pm1)
+ pm += ACPI_PM_OVRRUN;
+ lapic_cal_pm2 = pm;
+ lapic_cal_j2 = jiffies;
+ break;
+ }
+}
+
+static int __init calibrate_APIC_clock(void)
+{
+ struct clock_event_device *levt = &__get_cpu_var(lapic_events);
+ const long pm_100ms = PMTMR_TICKS_PER_SEC/10;
+ const long pm_thresh = pm_100ms/100;
+ void (*real_handler)(struct clock_event_device *dev);
+ unsigned long deltaj;
+ long delta, deltapm;
+ int pm_referenced = 0;
+
+ local_irq_disable();
+
+ /* Replace the global interrupt handler */
+ real_handler = global_clock_event->event_handler;
+ global_clock_event->event_handler = lapic_cal_handler;
+
+ /*
+ * Setup the APIC counter to 1e9. There is no way the lapic
+ * can underflow in the 100ms detection time frame
+ */
+ __setup_APIC_LVTT(1000000000, 0, 0);
+
+ /* Let the interrupts run */
+ local_irq_enable();
+
+ while (lapic_cal_loops <= LAPIC_CAL_LOOPS)
+ cpu_relax();
+
+ local_irq_disable();
+
+ /* Restore the real event handler */
+ global_clock_event->event_handler = real_handler;
+
+ /* Build delta t1-t2 as apic timer counts down */
+ delta = lapic_cal_t1 - lapic_cal_t2;
+ apic_printk(APIC_VERBOSE, "... lapic delta = %ld\n", delta);
+
+ /* Check, if the PM timer is available */
+ deltapm = lapic_cal_pm2 - lapic_cal_pm1;
+ apic_printk(APIC_VERBOSE, "... PM timer delta = %ld\n", deltapm);
+
+ if (deltapm) {
+ unsigned long mult;
+ u64 res;
+
+ mult = clocksource_hz2mult(PMTMR_TICKS_PER_SEC, 22);
+
+ if (deltapm > (pm_100ms - pm_thresh) &&
+ deltapm < (pm_100ms + pm_thresh)) {
+ apic_printk(APIC_VERBOSE, "... PM timer result ok\n");
+ } else {
+ res = (((u64) deltapm) * mult) >> 22;
+ do_div(res, 1000000);
+ printk(KERN_WARNING "APIC calibration not consistent "
+ "with PM Timer: %ldms instead of 100ms\n",
+ (long)res);
+ /* Correct the lapic counter value */
+ res = (((u64) delta) * pm_100ms);
+ do_div(res, deltapm);
+ printk(KERN_INFO "APIC delta adjusted to PM-Timer: "
+ "%lu (%ld)\n", (unsigned long) res, delta);
+ delta = (long) res;
+ }
+ pm_referenced = 1;
+ }
+
+ /* Calculate the scaled math multiplication factor */
+ lapic_clockevent.mult = div_sc(delta, TICK_NSEC * LAPIC_CAL_LOOPS,
+ lapic_clockevent.shift);
+ lapic_clockevent.max_delta_ns =
+ clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);
+ lapic_clockevent.min_delta_ns =
+ clockevent_delta2ns(0xF, &lapic_clockevent);
+
+ calibration_result = (delta * APIC_DIVISOR) / LAPIC_CAL_LOOPS;
+
+ apic_printk(APIC_VERBOSE, "..... delta %ld\n", delta);
+ apic_printk(APIC_VERBOSE, "..... mult: %ld\n", lapic_clockevent.mult);
+ apic_printk(APIC_VERBOSE, "..... calibration result: %u\n",
+ calibration_result);
+
+ if (cpu_has_tsc) {
+ delta = (long)(lapic_cal_tsc2 - lapic_cal_tsc1);
+ apic_printk(APIC_VERBOSE, "..... CPU clock speed is "
+ "%ld.%04ld MHz.\n",
+ (delta / LAPIC_CAL_LOOPS) / (1000000 / HZ),
+ (delta / LAPIC_CAL_LOOPS) % (1000000 / HZ));
+ }
+
+ apic_printk(APIC_VERBOSE, "..... host bus clock speed is "
+ "%u.%04u MHz.\n",
+ calibration_result / (1000000 / HZ),
+ calibration_result % (1000000 / HZ));
+
+ /*
+ * Do a sanity check on the APIC calibration result
+ */
+ if (calibration_result < (1000000 / HZ)) {
+ local_irq_enable();
+ printk(KERN_WARNING
+ "APIC frequency too slow, disabling apic timer\n");
+ return -1;
+ }
+
+ levt->features &= ~CLOCK_EVT_FEAT_DUMMY;
+
+ /* We trust the pm timer based calibration */
+ if (!pm_referenced) {
+ apic_printk(APIC_VERBOSE, "... verify APIC timer\n");
+
+ /*
+ * Setup the apic timer manually
+ */
+ levt->event_handler = lapic_cal_handler;
+ lapic_timer_setup(CLOCK_EVT_MODE_PERIODIC, levt);
+ lapic_cal_loops = -1;
+
+ /* Let the interrupts run */
+ local_irq_enable();
+
+ while (lapic_cal_loops <= LAPIC_CAL_LOOPS)
+ cpu_relax();
+
+ local_irq_disable();
+
+ /* Stop the lapic timer */
+ lapic_timer_setup(CLOCK_EVT_MODE_SHUTDOWN, levt);
+
+ local_irq_enable();
+
+ /* Jiffies delta */
+ deltaj = lapic_cal_j2 - lapic_cal_j1;
+ apic_printk(APIC_VERBOSE, "... jiffies delta = %lu\n", deltaj);
+
+ /* Check, if the jiffies result is consistent */
+ if (deltaj >= LAPIC_CAL_LOOPS-2 && deltaj <= LAPIC_CAL_LOOPS+2)
+ apic_printk(APIC_VERBOSE, "... jiffies result ok\n");
+ else
+ levt->features |= CLOCK_EVT_FEAT_DUMMY;
+ } else
+ local_irq_enable();
+
+ if (levt->features & CLOCK_EVT_FEAT_DUMMY) {
+ printk(KERN_WARNING
+ "APIC timer disabled due to verification failure.\n");
+ return -1;
+ }
+
+ return 0;
+}
+
+#endif
+
/*
* Setup the boot APIC
*
--
1.5.4.5