MIPS: Fix highmem.

Commit 35133692 (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>

arch/mips/include/asm/fixmap.h

@@ -108,6 +108,9 @@ static inline unsigned long virt_to_fix(const unsigned long vaddr)
 	return __virt_to_fix(vaddr);
 }
 
+#define kmap_get_fixmap_pte(vaddr)					\
+	pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)), (vaddr)), (vaddr))
+
 /*
  * Called from pgtable_init()
  */

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 */

arch/mips/mm/highmem.c

 #include <linux/module.h>
 #include <linux/highmem.h>
+#include <asm/fixmap.h>
 #include <asm/tlbflush.h>
 
+static pte_t *kmap_pte;
+
+unsigned long highstart_pfn, highend_pfn;
+
 void *__kmap(struct page *page)
 {
 	void *addr;
@@ -14,6 +19,7 @@ void *__kmap(struct page *page)
 
 	return addr;
 }
+EXPORT_SYMBOL(__kmap);
 
 void __kunmap(struct page *page)
 {
@@ -22,6 +28,7 @@ void __kunmap(struct page *page)
 		return;
 	kunmap_high(page);
 }
+EXPORT_SYMBOL(__kunmap);
 
 /*
  * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
@@ -48,11 +55,12 @@ void *__kmap_atomic(struct page *page, enum km_type type)
 #ifdef CONFIG_DEBUG_HIGHMEM
 	BUG_ON(!pte_none(*(kmap_pte - idx)));
 #endif
-	set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
+	set_pte(kmap_pte-idx, mk_pte(page, PAGE_KERNEL));
 	local_flush_tlb_one((unsigned long)vaddr);
 
 	return (void*) vaddr;
 }
+EXPORT_SYMBOL(__kmap_atomic);
 
 void __kunmap_atomic(void *kvaddr, enum km_type type)
 {
@@ -77,6 +85,7 @@ void __kunmap_atomic(void *kvaddr, enum km_type type)
 
 	pagefault_enable();
 }
+EXPORT_SYMBOL(__kunmap_atomic);
 
 /*
  * This is the same as kmap_atomic() but can map memory that doesn't
@@ -92,7 +101,7 @@ void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
 	debug_kmap_atomic(type);
 	idx = type + KM_TYPE_NR*smp_processor_id();
 	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
-	set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
+	set_pte(kmap_pte-idx, pfn_pte(pfn, PAGE_KERNEL));
 	flush_tlb_one(vaddr);
 
 	return (void*) vaddr;
@@ -111,7 +120,11 @@ struct page *__kmap_atomic_to_page(void *ptr)
 	return pte_page(*pte);
 }
 
-EXPORT_SYMBOL(__kmap);
-EXPORT_SYMBOL(__kunmap);
-EXPORT_SYMBOL(__kmap_atomic);
-EXPORT_SYMBOL(__kunmap_atomic);
+void __init kmap_init(void)
+{
+	unsigned long kmap_vstart;
+
+	/* cache the first kmap pte */
+	kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
+	kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
+}

arch/mips/mm/init.c

@@ -104,14 +104,6 @@ unsigned long setup_zero_pages(void)
 	return 1UL << order;
 }
 
-/*
- * These are almost like kmap_atomic / kunmap_atmic except they take an
- * additional address argument as the hint.
- */
-
-#define kmap_get_fixmap_pte(vaddr)					\
-	pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)), (vaddr)), (vaddr))
-
 #ifdef CONFIG_MIPS_MT_SMTC
 static pte_t *kmap_coherent_pte;
 static void __init kmap_coherent_init(void)
@@ -264,24 +256,6 @@ void copy_from_user_page(struct vm_area_struct *vma,
 	}
 }
 
-#ifdef CONFIG_HIGHMEM
-unsigned long highstart_pfn, highend_pfn;
-
-pte_t *kmap_pte;
-pgprot_t kmap_prot;
-
-static void __init kmap_init(void)
-{
-	unsigned long kmap_vstart;
-
-	/* cache the first kmap pte */
-	kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
-	kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
-
-	kmap_prot = PAGE_KERNEL;
-}
-#endif /* CONFIG_HIGHMEM */
-
 void __init fixrange_init(unsigned long start, unsigned long end,
 	pgd_t *pgd_base)
 {