x86_64: remove pit synchronization

The APIC timer setup code synchronizes the local APIC timer to the
PIT/HPET. This is pointless as the PIT and the local APIC timer
frequency are not correlated and the APIC timer calibration can never
be accurate enough to avoid that the local APIC timer and the PIT/HPET
drift apart.

Simply remove it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>

diff --git a/arch/x86/kernel/apic_64.c b/arch/x86/kernel/apic_64.c
index ce2f801..a73b443 100644 (file)
--- a/arch/x86/kernel/apic_64.c
+++ b/arch/x86/kernel/apic_64.c
@@ -790,24 +790,6 @@ static void setup_APIC_timer(unsigned int clocks)
 
        local_irq_save(flags);
 
-       /* wait for irq slice */
-       if (hpet_address && hpet_use_timer) {
-               u32 trigger = hpet_readl(HPET_T0_CMP);
-               while (hpet_readl(HPET_T0_CMP) == trigger)
-                       /* do nothing */ ;
-       } else {
-               int c1, c2;
-               outb_p(0x00, 0x43);
-               c2 = inb_p(0x40);
-               c2 |= inb_p(0x40) << 8;
-               do {
-                       c1 = c2;
-                       outb_p(0x00, 0x43);
-                       c2 = inb_p(0x40);
-                       c2 |= inb_p(0x40) << 8;
-               } while (c2 - c1 < 300);
-       }
-
        irqen = ! cpu_isset(smp_processor_id(),
                            timer_interrupt_broadcast_ipi_mask);
        __setup_APIC_LVTT(clocks, 0, irqen);