nds32: MMU definitions

This patch includes virtual memory layout, PHYS_OFFSET is defined as 0x0. It
also includes the 4KB/8KB page size configurations and pte operations.

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

arch/nds32/include/asm/pgalloc.h

@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#ifndef _ASMNDS32_PGALLOC_H
+#define _ASMNDS32_PGALLOC_H
+
+#include <asm/processor.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+#include <asm/proc-fns.h>
+
+/*
+ * Since we have only two-level page tables, these are trivial
+ */
+#define pmd_alloc_one(mm, addr)		({ BUG(); ((pmd_t *)2); })
+#define pmd_free(mm, pmd)			do { } while (0)
+#define pgd_populate(mm, pmd, pte)	BUG()
+#define pmd_pgtable(pmd) pmd_page(pmd)
+
+extern pgd_t *pgd_alloc(struct mm_struct *mm);
+extern void pgd_free(struct mm_struct *mm, pgd_t * pgd);
+
+#define check_pgt_cache()		do { } while (0)
+
+static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm,
+					  unsigned long addr)
+{
+	pte_t *pte;
+
+	pte =
+	    (pte_t *) __get_free_page(GFP_KERNEL | __GFP_RETRY_MAYFAIL |
+				      __GFP_ZERO);
+
+	return pte;
+}
+
+static inline pgtable_t pte_alloc_one(struct mm_struct *mm, unsigned long addr)
+{
+	pgtable_t pte;
+
+	pte = alloc_pages(GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_ZERO, 0);
+	if (pte)
+		cpu_dcache_wb_page((unsigned long)page_address(pte));
+
+	return pte;
+}
+
+/*
+ * Free one PTE table.
+ */
+static inline void pte_free_kernel(struct mm_struct *mm, pte_t * pte)
+{
+	if (pte) {
+		free_page((unsigned long)pte);
+	}
+}
+
+static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
+{
+	__free_page(pte);
+}
+
+/*
+ * Populate the pmdp entry with a pointer to the pte.  This pmd is part
+ * of the mm address space.
+ *
+ * Ensure that we always set both PMD entries.
+ */
+static inline void
+pmd_populate_kernel(struct mm_struct *mm, pmd_t * pmdp, pte_t * ptep)
+{
+	unsigned long pte_ptr = (unsigned long)ptep;
+	unsigned long pmdval;
+
+	BUG_ON(mm != &init_mm);
+
+	/*
+	 * The pmd must be loaded with the physical
+	 * address of the PTE table
+	 */
+	pmdval = __pa(pte_ptr) | _PAGE_KERNEL_TABLE;
+	set_pmd(pmdp, __pmd(pmdval));
+}
+
+static inline void
+pmd_populate(struct mm_struct *mm, pmd_t * pmdp, pgtable_t ptep)
+{
+	unsigned long pmdval;
+
+	BUG_ON(mm == &init_mm);
+
+	pmdval = page_to_pfn(ptep) << PAGE_SHIFT | _PAGE_USER_TABLE;
+	set_pmd(pmdp, __pmd(pmdval));
+}
+
+#endif