[PATCH] ppc32: Allow adjust of pfn offset in pte

Allow the pfn to be offset by more than just PAGE_SHIFT in the pte. Today,
PAGE_SHIFT tends to allow us to have 12-bits of flags in the pte. In the
future if we have a larger pte we can allocate more bits for flags by
offsetting the pfn even further.

Signed-off-by: Kumar Gala <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/asm-ppc/pgtable.h

···
  * Conversions between PTE values and page frame numbers.
  */
 
-#define pte_pfn(x)		(pte_val(x) >> PAGE_SHIFT)
+/* in some case we want to additionaly adjust where the pfn is in the pte to
+ * allow room for more flags */
+#define PFN_SHIFT_OFFSET	(PAGE_SHIFT)
+
+#define pte_pfn(x)		(pte_val(x) >> PFN_SHIFT_OFFSET)
 #define pte_page(x)		pfn_to_page(pte_pfn(x))
 
-#define pfn_pte(pfn, prot)	__pte(((pte_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
+#define pfn_pte(pfn, prot)	__pte(((pte_basic_t)(pfn) << PFN_SHIFT_OFFSET) |\
+					pgprot_val(prot))
 #define mk_pte(page, prot)	pfn_pte(page_to_pfn(page), prot)
 
 /*