MIPS: Rearrange PTE bits into fixed positions.

This patch rearranges the PTE bits into fixed positions for R2
and later cores. In the past, the TLB handling code did runtime
checking of RI/XI and adjusted the shifts and rotates in order
to fit the largest PFN value into the PTE. The checking now
occurs when building the TLB handler, thus eliminating those
checks. These new arrangements also define the largest possible
PFN value that can fit in the PTE. HUGE page support is only
available for 64-bit cores. Layouts of the PTE bits are now:

   64-bit, R1 or earlier:     CCC D V G [S H] M A W R P
   32-bit, R1 or earler:      CCC D V G M A W R P
   64-bit, R2 or later:       CCC D V G RI/R XI [S H] M A W P
   32-bit, R2 or later:       CCC D V G RI/R XI M A W P

[ralf@linux-mips.org: Fix another build error *rant* *rant*]

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9353/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 55 insertions, 28 deletions

diff --git a/arch/mips/include/asm/pgtable-bits.h b/arch/mips/include/asm/pgtable-bits.h
index 91747c2..8e432a8 100644
--- a/arch/mips/include/asm/pgtable-bits.h
+++ b/arch/mips/include/asm/pgtable-bits.h
@@ -95,11 +95,7 @@
 
 #else
 /*
- * When using the RI/XI bit support, we have 13 bits of flags below
- * the physical address. The RI/XI bits are placed such that a SRL 5
- * can strip off the software bits, then a ROTR 2 can move the RI/XI
- * into bits [63:62]. This also limits physical address to 56 bits,
- * which is more than we need right now.
+ * Below are the "Normal" R4K cases
  */
 
 /*
@@ -107,38 +103,59 @@
  */
 #define _PAGE_PRESENT_SHIFT	0
 #define _PAGE_PRESENT		(1 << _PAGE_PRESENT_SHIFT)
-#define _PAGE_READ_SHIFT	(cpu_has_rixi ? _PAGE_PRESENT_SHIFT : _PAGE_PRESENT_SHIFT + 1)
-#define _PAGE_READ ({BUG_ON(cpu_has_rixi); 1 << _PAGE_READ_SHIFT; })
+/* R2 or later cores check for RI/XI support to determine _PAGE_READ */
+#ifdef CONFIG_CPU_MIPSR2
+#define _PAGE_WRITE_SHIFT	(_PAGE_PRESENT_SHIFT + 1)
+#define _PAGE_WRITE		(1 << _PAGE_WRITE_SHIFT)
+#else
+#define _PAGE_READ_SHIFT	(_PAGE_PRESENT_SHIFT + 1)
+#define _PAGE_READ		(1 << _PAGE_READ_SHIFT)
 #define _PAGE_WRITE_SHIFT	(_PAGE_READ_SHIFT + 1)
 #define _PAGE_WRITE		(1 << _PAGE_WRITE_SHIFT)
+#endif
 #define _PAGE_ACCESSED_SHIFT	(_PAGE_WRITE_SHIFT + 1)
 #define _PAGE_ACCESSED		(1 << _PAGE_ACCESSED_SHIFT)
 #define _PAGE_MODIFIED_SHIFT	(_PAGE_ACCESSED_SHIFT + 1)
 #define _PAGE_MODIFIED		(1 << _PAGE_MODIFIED_SHIFT)
 
-#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
-/* huge tlb page */
+#if defined(CONFIG_64BIT) && defined(CONFIG_MIPS_HUGE_TLB_SUPPORT)
+/* Huge TLB page */
 #define _PAGE_HUGE_SHIFT	(_PAGE_MODIFIED_SHIFT + 1)
 #define _PAGE_HUGE		(1 << _PAGE_HUGE_SHIFT)
 #define _PAGE_SPLITTING_SHIFT	(_PAGE_HUGE_SHIFT + 1)
 #define _PAGE_SPLITTING		(1 << _PAGE_SPLITTING_SHIFT)
+
+/* Only R2 or newer cores have the XI bit */
+#ifdef CONFIG_CPU_MIPSR2
+#define _PAGE_NO_EXEC_SHIFT	(_PAGE_SPLITTING_SHIFT + 1)
 #else
-#define _PAGE_HUGE_SHIFT	(_PAGE_MODIFIED_SHIFT)
-#define _PAGE_HUGE		({BUG(); 1; })	/* Dummy value */
-#define _PAGE_SPLITTING_SHIFT	(_PAGE_HUGE_SHIFT)
-#define _PAGE_SPLITTING		({BUG(); 1; })	/* Dummy value */
-#endif
+#define _PAGE_GLOBAL_SHIFT	(_PAGE_SPLITTING_SHIFT + 1)
+#define _PAGE_GLOBAL		(1 << _PAGE_GLOBAL_SHIFT)
+#endif	/* CONFIG_CPU_MIPSR2 */
+
+#endif	/* CONFIG_64BIT && CONFIG_MIPS_HUGE_TLB_SUPPORT */
 
-/* Page cannot be executed */
-#define _PAGE_NO_EXEC_SHIFT	(cpu_has_rixi ? _PAGE_SPLITTING_SHIFT + 1 : _PAGE_SPLITTING_SHIFT)
-#define _PAGE_NO_EXEC		({BUG_ON(!cpu_has_rixi); 1 << _PAGE_NO_EXEC_SHIFT; })
+#ifdef CONFIG_CPU_MIPSR2
+/* XI - page cannot be executed */
+#ifndef _PAGE_NO_EXEC_SHIFT
+#define _PAGE_NO_EXEC_SHIFT	(_PAGE_MODIFIED_SHIFT + 1)
+#endif
+#define _PAGE_NO_EXEC		(cpu_has_rixi ? (1 << _PAGE_NO_EXEC_SHIFT) : 0)
 
-/* Page cannot be read */
-#define _PAGE_NO_READ_SHIFT	(cpu_has_rixi ? _PAGE_NO_EXEC_SHIFT + 1 : _PAGE_NO_EXEC_SHIFT)
-#define _PAGE_NO_READ		({BUG_ON(!cpu_has_rixi); 1 << _PAGE_NO_READ_SHIFT; })
+/* RI - page cannot be read */
+#define _PAGE_READ_SHIFT	(_PAGE_NO_EXEC_SHIFT + 1)
+#define _PAGE_READ		(cpu_has_rixi ? 0 : (1 << _PAGE_READ_SHIFT))
+#define _PAGE_NO_READ_SHIFT	_PAGE_READ_SHIFT
+#define _PAGE_NO_READ		(cpu_has_rixi ? (1 << _PAGE_READ_SHIFT) : 0)
 
 #define _PAGE_GLOBAL_SHIFT	(_PAGE_NO_READ_SHIFT + 1)
 #define _PAGE_GLOBAL		(1 << _PAGE_GLOBAL_SHIFT)
+
+#else	/* !CONFIG_CPU_MIPSR2 */
+#define _PAGE_GLOBAL_SHIFT	(_PAGE_MODIFIED_SHIFT + 1)
+#define _PAGE_GLOBAL		(1 << _PAGE_GLOBAL_SHIFT)
+#endif	/* CONFIG_CPU_MIPSR2 */
+
 #define _PAGE_VALID_SHIFT	(_PAGE_GLOBAL_SHIFT + 1)
 #define _PAGE_VALID		(1 << _PAGE_VALID_SHIFT)
 #define _PAGE_DIRTY_SHIFT	(_PAGE_VALID_SHIFT + 1)
@@ -150,18 +167,26 @@
 
 #endif /* defined(CONFIG_PHYS_ADDR_T_64BIT && defined(CONFIG_CPU_MIPS32) */
 
+#ifndef _PAGE_NO_EXEC
+#define _PAGE_NO_EXEC		0
+#endif
+#ifndef _PAGE_NO_READ
+#define _PAGE_NO_READ		0
+#endif
+
 #define _PAGE_SILENT_READ	_PAGE_VALID
 #define _PAGE_SILENT_WRITE	_PAGE_DIRTY
 
 #define _PFN_MASK		(~((1 << (_PFN_SHIFT)) - 1))
 
-#ifndef _PAGE_NO_READ
-#define _PAGE_NO_READ ({BUG(); 0; })
-#define _PAGE_NO_READ_SHIFT ({BUG(); 0; })
-#endif
-#ifndef _PAGE_NO_EXEC
-#define _PAGE_NO_EXEC ({BUG(); 0; })
-#endif
+/*
+ * The final layouts of the PTE bits are:
+ *
+ *   64-bit, R1 or earlier:     CCC D V G [S H] M A W R P
+ *   32-bit, R1 or earler:      CCC D V G M A W R P
+ *   64-bit, R2 or later:       CCC D V G RI/R XI [S H] M A W P
+ *   32-bit, R2 or later:       CCC D V G RI/R XI M A W P
+ */
 
 
 #ifndef __ASSEMBLY__
@@ -171,6 +196,7 @@
  */
 static inline uint64_t pte_to_entrylo(unsigned long pte_val)
 {
+#ifdef CONFIG_CPU_MIPSR2
 	if (cpu_has_rixi) {
 		int sa;
 #ifdef CONFIG_32BIT
@@ -186,6 +212,7 @@ static inline uint64_t pte_to_entrylo(unsigned long pte_val)
 		return (pte_val >> _PAGE_GLOBAL_SHIFT) |
 			((pte_val & (_PAGE_NO_EXEC | _PAGE_NO_READ)) << sa);
 	}
+#endif
 
 	return pte_val >> _PAGE_GLOBAL_SHIFT;
 }
@@ -245,7 +272,7 @@ static inline uint64_t pte_to_entrylo(unsigned long pte_val)
 #define _CACHE_UNCACHED_ACCELERATED	(7<<_CACHE_SHIFT)
 #endif
 
-#define __READABLE	(_PAGE_SILENT_READ | _PAGE_ACCESSED | (cpu_has_rixi ? 0 : _PAGE_READ))
+#define __READABLE	(_PAGE_SILENT_READ | _PAGE_READ | _PAGE_ACCESSED)
 #define __WRITEABLE	(_PAGE_SILENT_WRITE | _PAGE_WRITE | _PAGE_MODIFIED)
 
 #define _PAGE_CHG_MASK	(_PAGE_ACCESSED | _PAGE_MODIFIED |	\