MIPS: Fix highmem.

Commit 351336929ccf222ae38ff0cb7a8dd5fd5c6236a0 (kernel.org) rsp.
b3594a089f1c17ff919f8f78505c3f20e1f6f8ce (linux-mips.org):

> From: Chris Dearman <chris@mips.com>
> Date: Wed, 19 Sep 2007 00:58:24 +0100
> Subject: [PATCH] [MIPS] Allow setting of the cache attribute at run time.
>
> Slightly tacky, but there is a precedent in the sparc archirecture code.

introduces the variable _page_cachable_default, which defaults to zero and.
is used to create the prototype PTE for __kmap_atomic in
arch/mips/mm/init.c:kmap_init before initialization in
arch/mips/mm/c-r4k.c:coherency_setup, so the default value of 0 will be
used as the CCA of kmap atomic pages which on many processors is not a
defined CCA value and may result in writes to kmap_atomic pages getting
corrupted.  Debugged by Jon Fraser (jfraser@broadcom.com).

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

1 files changed, 4 insertions, 2 deletions

diff --git a/arch/mips/include/asm/highmem.h b/arch/mips/include/asm/highmem.h
index 4374ab2adc75..25adfb02923d 100644
--- a/arch/mips/include/asm/highmem.h
+++ b/arch/mips/include/asm/highmem.h
@@ -30,8 +30,6 @@
 /* declarations for highmem.c */
 extern unsigned long highstart_pfn, highend_pfn;
 
-extern pte_t *kmap_pte;
-extern pgprot_t kmap_prot;
 extern pte_t *pkmap_page_table;
 
 /*
@@ -62,6 +60,10 @@ extern struct page *__kmap_atomic_to_page(void *ptr);
 
 #define flush_cache_kmaps()     flush_cache_all()
 
+extern void kmap_init(void);
+
+#define kmap_prot PAGE_KERNEL
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_HIGHMEM_H */