[MIPS] Enable support for the userlocal hardware register

Which will cut down the cost of RDHWR $29 which is used to obtain the
TLS pointer and so far being emulated in software down to a single cycle
operation.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/cpu-probe.c

@@ -588,6 +588,8 @@ static inline unsigned int decode_config3(struct cpuinfo_mips *c)
 		c->options |= MIPS_CPU_VEIC;
 	if (config3 & MIPS_CONF3_MT)
 	        c->ases |= MIPS_ASE_MIPSMT;
+	if (config3 & MIPS_CONF3_ULRI)
+		c->options |= MIPS_CPU_ULRI;
 
 	return config3 & MIPS_CONF_M;
 }

arch/mips/kernel/syscall.c

@@ -272,9 +272,8 @@ asmlinkage int sys_set_thread_area(unsigned long addr)
 	struct thread_info *ti = task_thread_info(current);
 
 	ti->tp_value = addr;
-
-	/* If some future MIPS implementation has this register in hardware,
-	 * we will need to update it here (and in context switches).  */
+	if (cpu_has_userlocal)
+		write_c0_userlocal(addr);
 
 	return 0;
 }

arch/mips/kernel/traps.c

@@ -1341,7 +1341,14 @@ void __init per_cpu_trap_init(void)
 		set_c0_status(ST0_MX);
 
 #ifdef CONFIG_CPU_MIPSR2
-	write_c0_hwrena (0x0000000f); /* Allow rdhwr to all registers */
+	if (cpu_has_mips_r2) {
+		unsigned int enable = 0x0000000f;
+
+		if (cpu_has_userlocal)
+			enable |= (1 << 29);
+
+		write_c0_hwrena(enable);
+	}
 #endif
 
 #ifdef CONFIG_MIPS_MT_SMTC