nds32: Device specific operations

This patch introduces ioremap implementations.

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/mm/ioremap.c

@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/vmalloc.h>
+#include <linux/io.h>
+#include <linux/mm.h>
+#include <asm/pgtable.h>
+
+void __iomem *ioremap(phys_addr_t phys_addr, size_t size);
+
+static void __iomem *__ioremap_caller(phys_addr_t phys_addr, size_t size,
+				      void *caller)
+{
+	struct vm_struct *area;
+	unsigned long addr, offset, last_addr;
+	pgprot_t prot;
+
+	/* Don't allow wraparound or zero size */
+	last_addr = phys_addr + size - 1;
+	if (!size || last_addr < phys_addr)
+		return NULL;
+
+	/*
+	 * Mappings have to be page-aligned
+	 */
+	offset = phys_addr & ~PAGE_MASK;
+	phys_addr &= PAGE_MASK;
+	size = PAGE_ALIGN(last_addr + 1) - phys_addr;
+
+	/*
+	 * Ok, go for it..
+	 */
+	area = get_vm_area_caller(size, VM_IOREMAP, caller);
+	if (!area)
+		return NULL;
+
+	area->phys_addr = phys_addr;
+	addr = (unsigned long)area->addr;
+	prot = __pgprot(_PAGE_V | _PAGE_M_KRW | _PAGE_D |
+			_PAGE_G | _PAGE_C_DEV);
+	if (ioremap_page_range(addr, addr + size, phys_addr, prot)) {
+		vunmap((void *)addr);
+		return NULL;
+	}
+	return (__force void __iomem *)(offset + (char *)addr);
+
+}
+
+void __iomem *ioremap(phys_addr_t phys_addr, size_t size)
+{
+	return __ioremap_caller(phys_addr, size,
+				__builtin_return_address(0));
+}
+
+EXPORT_SYMBOL(ioremap);
+
+void iounmap(volatile void __iomem * addr)
+{
+	vunmap((void *)(PAGE_MASK & (unsigned long)addr));
+}
+
+EXPORT_SYMBOL(iounmap);