csky: MMU and page table management

This patch adds files related to memory management and here is our
memory-layout:

   Fixmap       : 0xffc02000 – 0xfffff000       (4 MB - 12KB)
   Pkmap        : 0xff800000 – 0xffc00000       (4 MB)
   Vmalloc      : 0xf0200000 – 0xff000000       (238 MB)
   Lowmem       : 0x80000000 – 0xc0000000       (1GB)

abiv1 CPU (CK610) is VIPT cache and it doesn't support highmem.
abiv2 CPUs are all PIPT cache and they could support highmem.

Lowmem is directly mapped by msa0 & msa1 reg, and we needn't setup
memory page table for it.

Link:https://lore.kernel.org/lkml/20180518215548.GH17671@n2100.armlinux.org.uk/
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

arch/csky/abiv2/inc/abi/ckmmu.h

@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#ifndef __ASM_CSKY_CKMMUV2_H
+#define __ASM_CSKY_CKMMUV2_H
+
+#include <abi/reg_ops.h>
+#include <asm/barrier.h>
+
+static inline int read_mmu_index(void)
+{
+	return mfcr("cr<0, 15>");
+}
+
+static inline void write_mmu_index(int value)
+{
+	mtcr("cr<0, 15>", value);
+}
+
+static inline int read_mmu_entrylo0(void)
+{
+	return mfcr("cr<2, 15>");
+}
+
+static inline int read_mmu_entrylo1(void)
+{
+	return mfcr("cr<3, 15>");
+}
+
+static inline void write_mmu_pagemask(int value)
+{
+	mtcr("cr<6, 15>", value);
+}
+
+static inline int read_mmu_entryhi(void)
+{
+	return mfcr("cr<4, 15>");
+}
+
+static inline void write_mmu_entryhi(int value)
+{
+	mtcr("cr<4, 15>", value);
+}
+
+/*
+ * TLB operations.
+ */
+static inline void tlb_probe(void)
+{
+	mtcr("cr<8, 15>", 0x80000000);
+}
+
+static inline void tlb_read(void)
+{
+	mtcr("cr<8, 15>", 0x40000000);
+}
+
+static inline void tlb_invalid_all(void)
+{
+#ifdef CONFIG_CPU_HAS_TLBI
+	asm volatile("tlbi.alls\n":::"memory");
+	sync_is();
+#else
+	mtcr("cr<8, 15>", 0x04000000);
+#endif
+}
+
+static inline void tlb_invalid_indexed(void)
+{
+	mtcr("cr<8, 15>", 0x02000000);
+}
+
+/* setup hardrefil pgd */
+static inline unsigned long get_pgd(void)
+{
+	return mfcr("cr<29, 15>");
+}
+
+static inline void setup_pgd(unsigned long pgd, bool kernel)
+{
+	if (kernel)
+		mtcr("cr<28, 15>", pgd);
+	else
+		mtcr("cr<29, 15>", pgd);
+}
+
+#endif /* __ASM_CSKY_CKMMUV2_H */

arch/csky/abiv2/inc/abi/page.h

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+static inline void clear_user_page(void *addr, unsigned long vaddr,
+				   struct page *page)
+{
+	clear_page(addr);
+}
+
+static inline void copy_user_page(void *to, void *from, unsigned long vaddr,
+				  struct page *page)
+{
+	copy_page(to, from);
+}

arch/csky/abiv2/inc/abi/pgtable-bits.h

@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#ifndef __ASM_CSKY_PGTABLE_BITS_H
+#define __ASM_CSKY_PGTABLE_BITS_H
+
+/* implemented in software */
+#define _PAGE_ACCESSED		(1<<7)
+#define PAGE_ACCESSED_BIT	(7)
+
+#define _PAGE_READ		(1<<8)
+#define _PAGE_WRITE		(1<<9)
+#define _PAGE_PRESENT		(1<<10)
+
+#define _PAGE_MODIFIED		(1<<11)
+#define PAGE_MODIFIED_BIT	(11)
+
+/* implemented in hardware */
+#define _PAGE_GLOBAL		(1<<0)
+
+#define _PAGE_VALID		(1<<1)
+#define PAGE_VALID_BIT		(1)
+
+#define _PAGE_DIRTY		(1<<2)
+#define PAGE_DIRTY_BIT		(2)
+
+#define _PAGE_SO		(1<<5)
+#define _PAGE_BUF		(1<<6)
+
+#define _PAGE_CACHE		(1<<3)
+
+#define _CACHE_MASK		_PAGE_CACHE
+
+#define _CACHE_CACHED		(_PAGE_VALID | _PAGE_CACHE | _PAGE_BUF)
+#define _CACHE_UNCACHED		(_PAGE_VALID | _PAGE_SO)
+
+#endif /* __ASM_CSKY_PGTABLE_BITS_H */