MIPS: pte_special()/pte_mkspecial() support

Add support for pte_special() & pte_mkspecial(), replacing our previous
stubs with functional implementations.

Signed-off-by: Dmitry Korotin <dkorotin@wavecomp.com>
[paul.burton@mips.com:
  - Fix for CONFIG_PHYS_ADDR_T_64BIT && CONFIG_CPU_MIPS32.
  - Rewrite commit message.]
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org

Author: Dmitry Korotin

arch/mips/Kconfig

@@ -82,6 +82,7 @@ config MIPS
 	select RTC_LIB
 	select SYSCTL_EXCEPTION_TRACE
 	select VIRT_TO_BUS
+	select ARCH_HAS_PTE_SPECIAL
 
 menu "Machine selection"
 

arch/mips/include/asm/pgtable-bits.h

@@ -52,6 +52,7 @@ enum pgtable_bits {
 	_PAGE_WRITE_SHIFT,
 	_PAGE_ACCESSED_SHIFT,
 	_PAGE_MODIFIED_SHIFT,
+	_PAGE_SPECIAL_SHIFT,
 };
 
 /*
@@ -78,6 +79,7 @@ enum pgtable_bits {
 	_PAGE_WRITE_SHIFT,
 	_PAGE_ACCESSED_SHIFT,
 	_PAGE_MODIFIED_SHIFT,
+	_PAGE_SPECIAL_SHIFT,
 };
 
 #elif defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
@@ -90,6 +92,7 @@ enum pgtable_bits {
 	_PAGE_WRITE_SHIFT,
 	_PAGE_ACCESSED_SHIFT,
 	_PAGE_MODIFIED_SHIFT,
+	_PAGE_SPECIAL_SHIFT,
 
 	/* Used by TLB hardware (placed in EntryLo) */
 	_PAGE_GLOBAL_SHIFT = 8,
@@ -113,6 +116,7 @@ enum pgtable_bits {
 #if defined(CONFIG_MIPS_HUGE_TLB_SUPPORT)
 	_PAGE_HUGE_SHIFT,
 #endif
+	_PAGE_SPECIAL_SHIFT,
 
 	/* Used by TLB hardware (placed in EntryLo*) */
 #if defined(CONFIG_CPU_HAS_RIXI)
@@ -135,6 +139,7 @@ enum pgtable_bits {
 #if defined(CONFIG_MIPS_HUGE_TLB_SUPPORT)
 # define _PAGE_HUGE		(1 << _PAGE_HUGE_SHIFT)
 #endif
+#define _PAGE_SPECIAL		(1 << _PAGE_SPECIAL_SHIFT)
 
 /* Used by TLB hardware (placed in EntryLo*) */
 #if defined(CONFIG_XPA)

arch/mips/include/asm/pgtable.h

@@ -277,6 +277,7 @@ extern pgd_t swapper_pg_dir[];
 static inline int pte_write(pte_t pte)	{ return pte.pte_low & _PAGE_WRITE; }
 static inline int pte_dirty(pte_t pte)	{ return pte.pte_low & _PAGE_MODIFIED; }
 static inline int pte_young(pte_t pte)	{ return pte.pte_low & _PAGE_ACCESSED; }
+static inline int pte_special(pte_t pte) { return pte.pte_low & _PAGE_SPECIAL; }
 
 static inline pte_t pte_wrprotect(pte_t pte)
 {
@@ -337,10 +338,17 @@ static inline pte_t pte_mkyoung(pte_t pte)
 	}
 	return pte;
 }
+
+static inline pte_t pte_mkspecial(pte_t pte)
+{
+	pte.pte_low |= _PAGE_SPECIAL;
+	return pte;
+}
 #else
 static inline int pte_write(pte_t pte)	{ return pte_val(pte) & _PAGE_WRITE; }
 static inline int pte_dirty(pte_t pte)	{ return pte_val(pte) & _PAGE_MODIFIED; }
 static inline int pte_young(pte_t pte)	{ return pte_val(pte) & _PAGE_ACCESSED; }
+static inline int pte_special(pte_t pte) { return pte_val(pte) & _PAGE_SPECIAL; }
 
 static inline pte_t pte_wrprotect(pte_t pte)
 {
@@ -384,6 +392,12 @@ static inline pte_t pte_mkyoung(pte_t pte)
 	return pte;
 }
 
+static inline pte_t pte_mkspecial(pte_t pte)
+{
+	pte_val(pte) |= _PAGE_SPECIAL;
+	return pte;
+}
+
 #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
 static inline int pte_huge(pte_t pte)	{ return pte_val(pte) & _PAGE_HUGE; }
 
@@ -394,8 +408,6 @@ static inline pte_t pte_mkhuge(pte_t pte)
 }
 #endif /* CONFIG_MIPS_HUGE_TLB_SUPPORT */
 #endif
-static inline int pte_special(pte_t pte)	{ return 0; }
-static inline pte_t pte_mkspecial(pte_t pte)	{ return pte; }
 
 /*
  * Macro to make mark a page protection value as "uncacheable".	 Note