[MIPS] Hook for platforms to define cachability of /dev/mem regions

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/mm/cache.c

@@ -6,6 +6,8 @@
  * Copyright (C) 1994 - 2003, 07 by Ralf Baechle (ralf@linux-mips.org)
  * Copyright (C) 2007 MIPS Technologies, Inc.
  */
+#include <linux/fs.h>
+#include <linux/fcntl.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -164,3 +166,11 @@ void __init cpu_cache_init(void)
 
 	panic(cache_panic);
 }
+
+int __weak __uncached_access(struct file *file, unsigned long addr)
+{
+	if (file->f_flags & O_SYNC)
+		return 1;
+
+	return addr >= __pa(high_memory);
+}

drivers/char/mem.c

@@ -75,6 +75,13 @@ static inline int uncached_access(struct file *file, unsigned long addr)
 	 * On ia64, we ignore O_SYNC because we cannot tolerate memory attribute aliases.
 	 */
 	return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
+#elif defined(CONFIG_MIPS)
+	{
+		extern int __uncached_access(struct file *file,
+					     unsigned long addr);
+
+		return __uncached_access(file, addr);
+	}
 #else
 	/*
 	 * Accessing memory above the top the kernel knows about or through a file pointer