From 1ade93efd0a3dda5b0c0afda8ab8f4bd12938c1b Mon Sep 17 00:00:00 2001 From: Jacob Pan Date: Thu, 10 Nov 2011 13:42:40 +0000 Subject: x86/apic: Allow use of lapic timer early calibration result 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 Signed-off-by: Jacob Pan Signed-off-by: Alan Cox Signed-off-by: Dirk Brandewie Signed-off-by: Ingo Molnar --- arch/x86/kernel/apic/apic.c | 33 ++++++++++++++++++++++++++------- 1 file changed, 26 insertions(+), 7 deletions(-) (limited to 'arch/x86/kernel') diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index a2fd72e0ab35..f98d84caf94c 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -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; -- cgit v1.2.3