x86/apic: Allow use of lapic timer early calibration result
authorJacob Pan <jacob.jun.pan@intel.com>
Thu, 10 Nov 2011 13:42:40 +0000 (13:42 +0000)
committerIngo Molnar <mingo@elte.hu>
Thu, 10 Nov 2011 15:20:57 +0000 (16:20 +0100)
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>
arch/x86/include/asm/apic.h
arch/x86/kernel/apic/apic.c

index 9b7273cb21937e8a884a08b45b3024af1bf3cfbc..1a6c09af048fbd587613c750502677d7cbb1c052 100644 (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);
index a2fd72e0ab35bbff6703836f82540a0f71588e85..f98d84caf94cfdc43cedda4cb411ebea5213e4b7 100644 (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;