1 files changed, 66 insertions, 0 deletions

diff --git a/arch/i386/kernel/timers/timer.c b/arch/i386/kernel/timers/timer.c
new file mode 100644
index 000000000000..a3d6a288088b
--- /dev/null
+++ b/arch/i386/kernel/timers/timer.c
@@ -0,0 +1,66 @@
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <asm/timer.h>
+
+#ifdef CONFIG_HPET_TIMER
+/*
+ * HPET memory read is slower than tsc reads, but is more dependable as it
+ * always runs at constant frequency and reduces complexity due to
+ * cpufreq. So, we prefer HPET timer to tsc based one. Also, we cannot use
+ * timer_pit when HPET is active. So, we default to timer_tsc.
+ */
+#endif
+/* list of timers, ordered by preference, NULL terminated */
+static struct init_timer_opts* __initdata timers[] = {
+#ifdef CONFIG_X86_CYCLONE_TIMER
+        &timer_cyclone_init,
+#endif
+#ifdef CONFIG_HPET_TIMER
+        &timer_hpet_init,
+#endif
+#ifdef CONFIG_X86_PM_TIMER
+        &timer_pmtmr_init,
+#endif
+        &timer_tsc_init,
+        &timer_pit_init,
+        NULL,
+};
+
+static char clock_override[10] __initdata;
+
+static int __init clock_setup(char* str)
+{
+        if (str)
+                strlcpy(clock_override, str, sizeof(clock_override));
+        return 1;
+}
+__setup("clock=", clock_setup);
+
+
+/* The chosen timesource has been found to be bad.
+ * Fall back to a known good timesource (the PIT)
+ */
+void clock_fallback(void)
+{
+        cur_timer = &timer_pit;
+}
+
+/* iterates through the list of timers, returning the first 
+ * one that initializes successfully.
+ */
+struct timer_opts* __init select_timer(void)
+{
+        int i = 0;
+        
+        /* find most preferred working timer */
+        while (timers[i]) {
+                if (timers[i]->init)
+                        if (timers[i]->init(clock_override) == 0)
+                                return timers[i]->opts;
+                ++i;
+        }
+                
+        panic("select_timer: Cannot find a suitable timer\n");
+        return NULL;
+}