[patch 7/8] x86 PAT: add pgprot_writecombine() interface for drivers

[Venkatesh Pallipadi]

Add pgprot_writecombine. pgprot_writecombine will be aliased to
pgprot_noncached when not supported by the architecture.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>

---
 arch/x86/include/asm/pgtable.h |    3 +++
 arch/x86/mm/pat.c              |    8 ++++++++
 include/asm-generic/pgtable.h  |    4 ++++
 3 files changed, 15 insertions(+)

Index: tip/include/asm-generic/pgtable.h
===================================================================
--- tip.orig/include/asm-generic/pgtable.h	2008-11-12 12:03:41.000000000 -0800
+++ tip/include/asm-generic/pgtable.h	2008-11-12 12:09:34.000000000 -0800
@@ -129,6 +129,10 @@ static inline void ptep_set_wrprotect(st
 #define move_pte(pte, prot, old_addr, new_addr)	(pte)
 #endif
 
+#ifndef pgprot_writecombine
+#define pgprot_writecombine pgprot_noncached
+#endif
+
 /*
  * When walking page tables, get the address of the next boundary,
  * or the end address of the range if that comes earlier.  Although no
Index: tip/arch/x86/include/asm/pgtable.h
===================================================================
--- tip.orig/arch/x86/include/asm/pgtable.h	2008-11-12 12:09:31.000000000 -0800
+++ tip/arch/x86/include/asm/pgtable.h	2008-11-12 12:09:34.000000000 -0800
@@ -168,6 +168,9 @@
 
 #ifndef __ASSEMBLY__
 
+#define pgprot_writecombine	pgprot_writecombine
+extern pgprot_t pgprot_writecombine(pgprot_t prot);
+
 /*
  * ZERO_PAGE is a global shared page that is always zero: used
  * for zero-mapped memory areas etc..
Index: tip/arch/x86/mm/pat.c
===================================================================
--- tip.orig/arch/x86/mm/pat.c	2008-11-12 12:06:50.000000000 -0800
+++ tip/arch/x86/mm/pat.c	2008-11-12 12:09:34.000000000 -0800
@@ -797,6 +797,14 @@ void untrack_pfn_vma(struct vm_area_stru
 	}
 }
 
+pgprot_t pgprot_writecombine(pgprot_t prot)
+{
+	if (pat_enabled)
+		return __pgprot(pgprot_val(prot) | _PAGE_CACHE_WC);
+	else
+		return pgprot_noncached(prot);
+}
+
 #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_PAT)
 
 /* get Nth element of the linked list */

-- 

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