+/* info on what we think the IO hole is */
+unsigned long io_hole_start;
+unsigned long io_hole_size;
+
+/*
+ * Do very early mm setup.
+ */
+void __init mm_init_ppc64(void)
+{
+#ifndef CONFIG_PPC_ISERIES
+ unsigned long i;
+#endif
+
+ ppc64_boot_msg(0x100, "MM Init");
+
+ /* This is the story of the IO hole... please, keep seated,
+ * unfortunately, we are out of oxygen masks at the moment.
+ * So we need some rough way to tell where your big IO hole
+ * is. On pmac, it's between 2G and 4G, on POWER3, it's around
+ * that area as well, on POWER4 we don't have one, etc...
+ * We need that as a "hint" when sizing the TCE table on POWER3
+ * So far, the simplest way that seem work well enough for us it
+ * to just assume that the first discontinuity in our physical
+ * RAM layout is the IO hole. That may not be correct in the future
+ * (and isn't on iSeries but then we don't care ;)
+ */
+
+#ifndef CONFIG_PPC_ISERIES
+ for (i = 1; i < lmb.memory.cnt; i++) {
+ unsigned long base, prevbase, prevsize;
+
+ prevbase = lmb.memory.region[i-1].base;
+ prevsize = lmb.memory.region[i-1].size;
+ base = lmb.memory.region[i].base;
+ if (base > (prevbase + prevsize)) {
+ io_hole_start = prevbase + prevsize;
+ io_hole_size = base - (prevbase + prevsize);
+ break;
+ }
+ }
+#endif /* CONFIG_PPC_ISERIES */
+ if (io_hole_start)
+ printk("IO Hole assumed to be %lx -> %lx\n",
+ io_hole_start, io_hole_start + io_hole_size - 1);
+
+ ppc64_boot_msg(0x100, "MM Init Done");
+}
+