MIPS: cpu-features: Add cpu_has_ftlb

Add cpu_has_ftlb, which specifies that an FTLB is present in addition to
the VTLB, probed based on whether Config.MT == 4 (rather than 1 for
standard JTLB).

This is necessary since MIPS release 6 removes Config4.MMUExtDef, so the
presence of the FTLB fields in Config4 must be determined from Config.MT
instead.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11159/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/cpu-probe.c

@@ -410,16 +410,18 @@ static int set_ftlb_enable(struct cpuinfo_mips *c, int enable)
 static inline unsigned int decode_config0(struct cpuinfo_mips *c)
 {
 	unsigned int config0;
-	int isa;
+	int isa, mt;
 
 	config0 = read_c0_config();
 
 	/*
 	 * Look for Standard TLB or Dual VTLB and FTLB
 	 */
-	if ((((config0 & MIPS_CONF_MT) >> 7) == 1) ||
-	    (((config0 & MIPS_CONF_MT) >> 7) == 4))
+	mt = config0 & MIPS_CONF_MT;
+	if (mt == MIPS_CONF_MT_TLB)
 		c->options |= MIPS_CPU_TLB;
+	else if (mt == MIPS_CONF_MT_FTLB)
+		c->options |= MIPS_CPU_TLB | MIPS_CPU_FTLB;
 
 	isa = (config0 & MIPS_CONF_AT) >> 13;
 	switch (isa) {