MIPS: Decode c0_config4 for large TLBs.

For processors that have more than 64 TLBs, we need to decode both
config1 and config4 to determine the total number TLBs.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/866/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/mipsregs.h

@@ -576,6 +576,10 @@
 #define MIPS_CONF3_DSP		(_ULCAST_(1) << 10)
 #define MIPS_CONF3_ULRI		(_ULCAST_(1) << 13)
 
+#define MIPS_CONF4_MMUSIZEEXT	(_ULCAST_(255) << 0)
+#define MIPS_CONF4_MMUEXTDEF	(_ULCAST_(3) << 14)
+#define MIPS_CONF4_MMUEXTDEF_MMUSIZEEXT (_ULCAST_(1) << 14)
+
 #define MIPS_CONF7_WII		(_ULCAST_(1) << 31)
 
 #define MIPS_CONF7_RPS		(_ULCAST_(1) << 2)

arch/mips/kernel/cpu-probe.c

@@ -700,6 +700,19 @@ static inline unsigned int decode_config3(struct cpuinfo_mips *c)
 	return config3 & MIPS_CONF_M;
 }
 
+static inline unsigned int decode_config4(struct cpuinfo_mips *c)
+{
+	unsigned int config4;
+
+	config4 = read_c0_config4();
+
+	if ((config4 & MIPS_CONF4_MMUEXTDEF) == MIPS_CONF4_MMUEXTDEF_MMUSIZEEXT
+	    && cpu_has_tlb)
+		c->tlbsize += (config4 & MIPS_CONF4_MMUSIZEEXT) * 0x40;
+
+	return config4 & MIPS_CONF_M;
+}
+
 static void __cpuinit decode_configs(struct cpuinfo_mips *c)
 {
 	int ok;
@@ -718,6 +731,8 @@ static void __cpuinit decode_configs(struct cpuinfo_mips *c)
 		ok = decode_config2(c);
 	if (ok)
 		ok = decode_config3(c);
+	if (ok)
+		ok = decode_config4(c);
 
 	mips_probe_watch_registers(c);
 }