[patch-mm 20/33] x86_64: remove pit synchronization

[Thomas Gleixner <tglx@linutronix.de>]

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>

---
 arch/x86_64/kernel/apic.c |   20 --------------------
 1 file changed, 20 deletions(-)

Index: linux-2.6.22-rc6-mm/arch/x86_64/kernel/apic.c
===================================================================
--- linux-2.6.22-rc6-mm.orig/arch/x86_64/kernel/apic.c	2007-07-15 17:39:44.000000000 +0200
+++ linux-2.6.22-rc6-mm/arch/x86_64/kernel/apic.c	2007-07-15 17:48:58.000000000 +0200
@@ -791,26 +791,6 @@ static void setup_APIC_timer(unsigned in
 
 	local_irq_save(flags);
 
-	/* wait for irq slice */
-	if (hpet_address && hpet_use_timer) {
-		int trigger = hpet_readl(HPET_T0_CMP);
-		while (hpet_readl(HPET_COUNTER) >= trigger)
-			/* do nothing */ ;
-		while (hpet_readl(HPET_COUNTER) <  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);

-- 

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