Initial commit; kernel source import

arch/x86/kernel/i8253.c

@@ -0,0 +1,43 @@
+/*
+ * 8253/PIT functions
+ *
+ */
+#include <linux/clockchips.h>
+#include <linux/module.h>
+#include <linux/timex.h>
+#include <linux/i8253.h>
+
+#include <asm/hpet.h>
+#include <asm/time.h>
+#include <asm/smp.h>
+
+/*
+ * HPET replaces the PIT, when enabled. So we need to know, which of
+ * the two timers is used
+ */
+struct clock_event_device *global_clock_event;
+
+void __init setup_pit_timer(void)
+{
+	clockevent_i8253_init(true);
+	global_clock_event = &i8253_clockevent;
+}
+
+#ifndef CONFIG_X86_64
+static int __init init_pit_clocksource(void)
+{
+	 /*
+	  * Several reasons not to register PIT as a clocksource:
+	  *
+	  * - On SMP PIT does not scale due to i8253_lock
+	  * - when HPET is enabled
+	  * - when local APIC timer is active (PIT is switched off)
+	  */
+	if (num_possible_cpus() > 1 || is_hpet_enabled() ||
+	    i8253_clockevent.mode != CLOCK_EVT_MODE_PERIODIC)
+		return 0;
+
+	return clocksource_i8253_init();
+}
+arch_initcall(init_pit_clocksource);
+#endif /* !CONFIG_X86_64 */