xtensa: nommu support

Add support for !CONFIG_MMU setups.

Signed-off-by: Johannes Weiner <jw@emlix.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

arch/xtensa/mm/mmu.c

@@ -0,0 +1,70 @@
+/*
+ * xtensa mmu stuff
+ *
+ * Extracted from init.c
+ */
+#include <linux/percpu.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/cache.h>
+
+#include <asm/tlb.h>
+#include <asm/tlbflush.h>
+#include <asm/mmu_context.h>
+#include <asm/page.h>
+
+DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
+
+void __init paging_init(void)
+{
+	memset(swapper_pg_dir, 0, PAGE_SIZE);
+}
+
+/*
+ * Flush the mmu and reset associated register to default values.
+ */
+void __init init_mmu(void)
+{
+	/* Writing zeros to the <t>TLBCFG special registers ensure
+	 * that valid values exist in the register.  For existing
+	 * PGSZID<w> fields, zero selects the first element of the
+	 * page-size array.  For nonexistent PGSZID<w> fields, zero is
+	 * the best value to write.  Also, when changing PGSZID<w>
+	 * fields, the corresponding TLB must be flushed.
+	 */
+	set_itlbcfg_register(0);
+	set_dtlbcfg_register(0);
+	flush_tlb_all();
+
+	/* Set rasid register to a known value. */
+
+	set_rasid_register(ASID_USER_FIRST);
+
+	/* Set PTEVADDR special register to the start of the page
+	 * table, which is in kernel mappable space (ie. not
+	 * statically mapped).  This register's value is undefined on
+	 * reset.
+	 */
+	set_ptevaddr_register(PGTABLE_START);
+}
+
+struct kmem_cache *pgtable_cache __read_mostly;
+
+static void pgd_ctor(void *addr)
+{
+	pte_t *ptep = (pte_t *)addr;
+	int i;
+
+	for (i = 0; i < 1024; i++, ptep++)
+		pte_clear(NULL, 0, ptep);
+
+}
+
+void __init pgtable_cache_init(void)
+{
+	pgtable_cache = kmem_cache_create("pgd",
+			PAGE_SIZE, PAGE_SIZE,
+			SLAB_HWCACHE_ALIGN,
+			pgd_ctor);
+}