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x86/apic: Allow use of lapic timer early calibration result

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lapic timer calibration can be combined with tsc in platform
specific calibration functions. if such calibration result is
obtained early, we can skip the redundant calibration loops.

Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dirk Brandewie <dirk.brandewie@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jacob Pan 2011-11-10 13:42:40 +00:00 committed by Ingo Molnar
parent bb84ac2d3a
commit 1ade93efd0
2 changed files with 27 additions and 7 deletions
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1
arch/x86/include/asm/apic.h
View file

@ -49,6 +49,7 @@ extern unsigned int apic_verbosity;
extern int local_apic_timer_c2_ok;
extern int disable_apic;
extern unsigned int lapic_timer_frequency;
#ifdef CONFIG_SMP
extern void __inquire_remote_apic(int apicid);

33
arch/x86/kernel/apic/apic.c
View file

@ -186,7 +186,7 @@ static struct resource lapic_resource = {
.flags = IORESOURCE_MEM | IORESOURCE_BUSY,
};
static unsigned int calibration_result;
unsigned int lapic_timer_frequency = 0;
static void apic_pm_activate(void);
@ -454,7 +454,7 @@ static void lapic_timer_setup(enum clock_event_mode mode,
switch (mode) {
case CLOCK_EVT_MODE_PERIODIC:
case CLOCK_EVT_MODE_ONESHOT:
__setup_APIC_LVTT(calibration_result,
__setup_APIC_LVTT(lapic_timer_frequency,
mode != CLOCK_EVT_MODE_PERIODIC, 1);
break;
case CLOCK_EVT_MODE_UNUSED:
@ -638,6 +638,25 @@ static int __init calibrate_APIC_clock(void)
long delta, deltatsc;
int pm_referenced = 0;
/**
* check if lapic timer has already been calibrated by platform
* specific routine, such as tsc calibration code. if so, we just fill
* in the clockevent structure and return.
*/
if (lapic_timer_frequency) {
apic_printk(APIC_VERBOSE, "lapic timer already calibrated %d\n",
lapic_timer_frequency);
lapic_clockevent.mult = div_sc(lapic_timer_frequency/APIC_DIVISOR,
TICK_NSEC, lapic_clockevent.shift);
lapic_clockevent.max_delta_ns =
clockevent_delta2ns(0x7FFFFF, &lapic_clockevent);
lapic_clockevent.min_delta_ns =
clockevent_delta2ns(0xF, &lapic_clockevent);
lapic_clockevent.features &= ~CLOCK_EVT_FEAT_DUMMY;
return 0;
}
local_irq_disable();
/* Replace the global interrupt handler */
@ -679,12 +698,12 @@ static int __init calibrate_APIC_clock(void)
lapic_clockevent.min_delta_ns =
clockevent_delta2ns(0xF, &lapic_clockevent);
calibration_result = (delta * APIC_DIVISOR) / LAPIC_CAL_LOOPS;
lapic_timer_frequency = (delta * APIC_DIVISOR) / LAPIC_CAL_LOOPS;
apic_printk(APIC_VERBOSE, "..... delta %ld\n", delta);
apic_printk(APIC_VERBOSE, "..... mult: %u\n", lapic_clockevent.mult);
apic_printk(APIC_VERBOSE, "..... calibration result: %u\n",
calibration_result);
lapic_timer_frequency);
if (cpu_has_tsc) {
apic_printk(APIC_VERBOSE, "..... CPU clock speed is "
@ -695,13 +714,13 @@ static int __init calibrate_APIC_clock(void)
apic_printk(APIC_VERBOSE, "..... host bus clock speed is "
"%u.%04u MHz.\n",
calibration_result / (1000000 / HZ),
calibration_result % (1000000 / HZ));
lapic_timer_frequency / (1000000 / HZ),
lapic_timer_frequency % (1000000 / HZ));
/*
* Do a sanity check on the APIC calibration result
*/
if (calibration_result < (1000000 / HZ)) {
if (lapic_timer_frequency < (1000000 / HZ)) {
local_irq_enable();
pr_warning("APIC frequency too slow, disabling apic timer\n");
return -1;