x86_64: remove pit synchronization (500ff08b) · Commits · e / devices / android_kernel_sony_msm8998

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>

arch/x86/kernel/apic_64.c

+0 −18

Original line number	Original line	Diff line number	Diff line
	@@ -790,24 +790,6 @@ static void setup_APIC_timer(unsigned int clocks)

	local_irq_save(flags);		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(),		irqen = ! cpu_isset(smp_processor_id(),
	timer_interrupt_broadcast_ipi_mask);		timer_interrupt_broadcast_ipi_mask);
	__setup_APIC_LVTT(clocks, 0, irqen);		__setup_APIC_LVTT(clocks, 0, irqen);