MIPS: only register FTLBPar exception handler for supported models

Previously ExcCode 16 is unconditionally treated as the FTLB parity
exception (FTLBPar), but in fact its semantic is implementation-
dependent. Looking at various manuals it seems the FTLBPar exception is
only present on some recent MIPS Technologies cores, so only register
the handler on these.

Fixes: 75b5b5e ("MIPS: Add support for FTLBs")
Reviewed-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: WANG Xuerui <git@xen0n.name>
Cc: Paul Burton <paulburton@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Author: xen0n

arch/mips/include/asm/cpu-features.h

@@ -568,6 +568,10 @@
 # define cpu_has_mac2008_only	__opt(MIPS_CPU_MAC_2008_ONLY)
 #endif
 
+#ifndef cpu_has_ftlbparex
+# define cpu_has_ftlbparex	__opt(MIPS_CPU_FTLBPAREX)
+#endif
+
 #ifdef CONFIG_SMP
 /*
  * Some systems share FTLB RAMs between threads within a core (siblings in

arch/mips/include/asm/cpu.h

@@ -427,6 +427,7 @@ enum cpu_type_enum {
 #define MIPS_CPU_MM_SYSAD	BIT_ULL(58)	/* CPU supports write-through SysAD Valid merge */
 #define MIPS_CPU_MM_FULL	BIT_ULL(59)	/* CPU supports write-through full merge */
 #define MIPS_CPU_MAC_2008_ONLY	BIT_ULL(60)	/* CPU Only support MAC2008 Fused multiply-add instruction */
+#define MIPS_CPU_FTLBPAREX	BIT_ULL(61)	/* CPU has FTLB parity exception */
 
 /*
  * CPU ASE encodings

arch/mips/kernel/cpu-probe.c

@@ -1827,6 +1827,19 @@ static inline void cpu_probe_mips(struct cpuinfo_mips *c, unsigned int cpu)
 	default:
 		break;
 	}
+
+	/* Recent MIPS cores use the implementation-dependent ExcCode 16 for
+	 * cache/FTLB parity exceptions.
+	 */
+	switch (__get_cpu_type(c->cputype)) {
+	case CPU_PROAPTIV:
+	case CPU_P5600:
+	case CPU_P6600:
+	case CPU_I6400:
+	case CPU_I6500:
+		c->options |= MIPS_CPU_FTLBPAREX;
+		break;
+	}
 }
 
 static inline void cpu_probe_alchemy(struct cpuinfo_mips *c, unsigned int cpu)

arch/mips/kernel/traps.c

@@ -2454,7 +2454,8 @@ void __init trap_init(void)
 	if (cpu_has_fpu && !cpu_has_nofpuex)
 		set_except_vector(EXCCODE_FPE, handle_fpe);
 
-	set_except_vector(MIPS_EXCCODE_TLBPAR, handle_ftlb);
+	if (cpu_has_ftlbparex)
+		set_except_vector(MIPS_EXCCODE_TLBPAR, handle_ftlb);
 
 	if (cpu_has_rixiex) {
 		set_except_vector(EXCCODE_TLBRI, tlb_do_page_fault_0);