+#ifdef CONFIG_X86_64
+/*
+ * apic_is_clustered_box() -- Check if we can expect good TSC
+ *
+ * Thus far, the major user of this is IBM's Summit2 series:
+ *
+ * Clustered boxes may have unsynced TSC problems if they are
+ * multi-chassis. Use available data to take a good guess.
+ * If in doubt, go HPET.
+ */
+__cpuinit int apic_is_clustered_box(void)
+{
+ int i, clusters, zeros;
+ unsigned id;
+ u16 *bios_cpu_apicid;
+ DECLARE_BITMAP(clustermap, NUM_APIC_CLUSTERS);
+
+ /*
+ * there is not this kind of box with AMD CPU yet.
+ * Some AMD box with quadcore cpu and 8 sockets apicid
+ * will be [4, 0x23] or [8, 0x27] could be thought to
+ * vsmp box still need checking...
+ */
+ if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && !is_vsmp_box())
+ return 0;
+
+ bios_cpu_apicid = early_per_cpu_ptr(x86_bios_cpu_apicid);
+ bitmap_zero(clustermap, NUM_APIC_CLUSTERS);
+
+ for (i = 0; i < NR_CPUS; i++) {
+ /* are we being called early in kernel startup? */
+ if (bios_cpu_apicid) {
+ id = bios_cpu_apicid[i];
+ }
+ else if (i < nr_cpu_ids) {
+ if (cpu_present(i))
+ id = per_cpu(x86_bios_cpu_apicid, i);
+ else
+ continue;
+ }
+ else
+ break;