[MIPS] TX49XX has prefetch.

    
The TX49XX has the prefetch instruction.  It supports only Pref_Load
(hint 0).  Actually changes in this patch except for Kconfig are not
have any effects, I added these changes to prevent misuse of unsupported
hints.
    
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -1160,6 +1160,7 @@ config CPU_R4X00
 config CPU_TX49XX
 	bool "R49XX"
 	depends on SYS_HAS_CPU_TX49XX
+	select CPU_HAS_PREFETCH
 	select CPU_SUPPORTS_32BIT_KERNEL
 	select CPU_SUPPORTS_64BIT_KERNEL
 

arch/mips/mm/c-r4k.c

@@ -786,6 +786,7 @@ static void __init probe_pcache(void)
 		c->dcache.waybit = 0;
 
 		c->options |= MIPS_CPU_CACHE_CDEX_P;
+		c->options |= MIPS_CPU_PREFETCH;
 		break;
 
 	case CPU_R4000PC:

arch/mips/mm/pg-r4k.c

@@ -124,7 +124,7 @@ static inline void build_nop(void)
 
 static inline void build_src_pref(int advance)
 {
-	if (!(load_offset & (cpu_dcache_line_size() - 1))) {
+	if (!(load_offset & (cpu_dcache_line_size() - 1)) && advance) {
 		union mips_instruction mi;
 
 		mi.i_format.opcode     = pref_op;
@@ -166,7 +166,7 @@ static inline void build_load_reg(int reg)
 
 static inline void build_dst_pref(int advance)
 {
-	if (!(store_offset & (cpu_dcache_line_size() - 1))) {
+	if (!(store_offset & (cpu_dcache_line_size() - 1)) && advance) {
 		union mips_instruction mi;
 
 		mi.i_format.opcode     = pref_op;
@@ -340,6 +340,12 @@ void __init build_clear_page(void)
 
 	if (cpu_has_prefetch) {
 		switch (current_cpu_data.cputype) {
+		case CPU_TX49XX:
+			/* TX49 supports only Pref_Load */
+			pref_offset_clear = 0;
+			pref_offset_copy = 0;
+			break;
+
 		case CPU_RM9000:
 			/*
 			 * As a workaround for erratum G105 which make the