MIPS: Loongson64: Probe CPU features via CPUCFG

CPUCFG is a Loongson self-defined instruction used to mark CPU
features for Loongson processors started from Loongson-3A4000.

Slightly adjust cpu_probe_loongson function as well. Remove features
that already probed via decode_configs in processor's PRID case
and add a comment about TLBINV.
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/kernel/cpu-probe.c

@@ -1932,8 +1932,35 @@ static inline void cpu_probe_cavium(struct cpuinfo_mips *c, unsigned int cpu)
 	}
 }
 
+#ifdef CONFIG_CPU_LOONGSON64
+#include <loongson_regs.h>
+
+static inline void decode_cpucfg(struct cpuinfo_mips *c)
+{
+	u32 cfg1 = read_cpucfg(LOONGSON_CFG1);
+	u32 cfg2 = read_cpucfg(LOONGSON_CFG2);
+	u32 cfg3 = read_cpucfg(LOONGSON_CFG3);
+
+	if (cfg1 & LOONGSON_CFG1_MMI)
+		c->ases |= MIPS_ASE_LOONGSON_MMI;
+
+	if (cfg2 & LOONGSON_CFG2_LEXT1)
+		c->ases |= MIPS_ASE_LOONGSON_EXT;
+
+	if (cfg2 & LOONGSON_CFG2_LEXT2)
+		c->ases |= MIPS_ASE_LOONGSON_EXT2;
+
+	if (cfg2 & LOONGSON_CFG2_LSPW)
+		c->options |= MIPS_CPU_LDPTE;
+
+	if (cfg3 & LOONGSON_CFG3_LCAMP)
+		c->ases |= MIPS_ASE_LOONGSON_CAM;
+}
+
 static inline void cpu_probe_loongson(struct cpuinfo_mips *c, unsigned int cpu)
 {
+	decode_configs(c);
+
 	switch (c->processor_id & PRID_IMP_MASK) {
 	case PRID_IMP_LOONGSON_64R: /* Loongson-64 Reduced */
 		switch (c->processor_id & PRID_REV_MASK) {
@@ -1947,7 +1974,6 @@ static inline void cpu_probe_loongson(struct cpuinfo_mips *c, unsigned int cpu)
 			set_isa(c, MIPS_CPU_ISA_M64R2);
 			break;
 		}
-		decode_configs(c);
 		c->writecombine = _CACHE_UNCACHED_ACCELERATED;
 		c->ases |= (MIPS_ASE_LOONGSON_MMI | MIPS_ASE_LOONGSON_EXT |
 				MIPS_ASE_LOONGSON_EXT2);
@@ -1969,9 +1995,12 @@ static inline void cpu_probe_loongson(struct cpuinfo_mips *c, unsigned int cpu)
 			set_isa(c, MIPS_CPU_ISA_M64R2);
 			break;
 		}
-
-		decode_configs(c);
-		c->options |= MIPS_CPU_FTLB | MIPS_CPU_TLBINV | MIPS_CPU_LDPTE;
+		/*
+		 * Loongson-3 Classic did not implement MIPS standard TLBINV
+		 * but implemented TLBINVF and EHINV. As currently we're only
+		 * using these two features, enable MIPS_CPU_TLBINV as well.
+		 */
+		c->options |= MIPS_CPU_TLBINV | MIPS_CPU_LDPTE;
 		c->writecombine = _CACHE_UNCACHED_ACCELERATED;
 		c->ases |= (MIPS_ASE_LOONGSON_MMI | MIPS_ASE_LOONGSON_CAM |
 			MIPS_ASE_LOONGSON_EXT | MIPS_ASE_LOONGSON_EXT2);
@@ -1981,17 +2010,17 @@ static inline void cpu_probe_loongson(struct cpuinfo_mips *c, unsigned int cpu)
 		__cpu_name[cpu] = "ICT Loongson-3";
 		set_elf_platform(cpu, "loongson3a");
 		set_isa(c, MIPS_CPU_ISA_M64R2);
-		decode_configs(c);
-		c->options |= MIPS_CPU_FTLB | MIPS_CPU_TLBINV | MIPS_CPU_LDPTE;
+		decode_cpucfg(c);
 		c->writecombine = _CACHE_UNCACHED_ACCELERATED;
-		c->ases |= (MIPS_ASE_LOONGSON_MMI | MIPS_ASE_LOONGSON_CAM |
-			MIPS_ASE_LOONGSON_EXT | MIPS_ASE_LOONGSON_EXT2);
 		break;
 	default:
 		panic("Unknown Loongson Processor ID!");
 		break;
 	}
 }
+#else
+static inline void cpu_probe_loongson(struct cpuinfo_mips *c, unsigned int cpu) { }
+#endif
 
 static inline void cpu_probe_ingenic(struct cpuinfo_mips *c, unsigned int cpu)
 {