MIPS: Detect the MSA ASE

This patch adds support for probing the MSAP bit within the Config3
register in order to detect the presence of the MSA ASE. Presence of the
ASE will be indicated in /proc/cpuinfo. The value of the MSA
implementation register will be displayed at boot to aid debugging and
verification of a correct setup, as is done for the FPU.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6430/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/cpu-probe.c

@@ -23,6 +23,7 @@
 #include <asm/cpu-type.h>
 #include <asm/fpu.h>
 #include <asm/mipsregs.h>
+#include <asm/msa.h>
 #include <asm/watch.h>
 #include <asm/elf.h>
 #include <asm/spram.h>
@@ -126,6 +127,20 @@ static inline int __cpu_has_fpu(void)
 	return ((cpu_get_fpu_id() & FPIR_IMP_MASK) != FPIR_IMP_NONE);
 }
 
+static inline unsigned long cpu_get_msa_id(void)
+{
+	unsigned long status, conf5, msa_id;
+
+	status = read_c0_status();
+	__enable_fpu(FPU_64BIT);
+	conf5 = read_c0_config5();
+	enable_msa();
+	msa_id = read_msa_ir();
+	write_c0_config5(conf5);
+	write_c0_status(status);
+	return msa_id;
+}
+
 static inline void cpu_probe_vmbits(struct cpuinfo_mips *c)
 {
 #ifdef __NEED_VMBITS_PROBE
@@ -301,6 +316,8 @@ static inline unsigned int decode_config3(struct cpuinfo_mips *c)
 		c->ases |= MIPS_ASE_VZ;
 	if (config3 & MIPS_CONF3_SC)
 		c->options |= MIPS_CPU_SEGMENTS;
+	if (config3 & MIPS_CONF3_MSA)
+		c->ases |= MIPS_ASE_MSA;
 
 	return config3 & MIPS_CONF_M;
 }
@@ -1178,6 +1195,9 @@ void cpu_probe(void)
 	else
 		c->srsets = 1;
 
+	if (cpu_has_msa)
+		c->msa_id = cpu_get_msa_id();
+
 	cpu_probe_vmbits(c);
 
 #ifdef CONFIG_64BIT
@@ -1194,4 +1214,6 @@ void cpu_report(void)
 		smp_processor_id(), c->processor_id, cpu_name_string());
 	if (c->options & MIPS_CPU_FPU)
 		printk(KERN_INFO "FPU revision is: %08x\n", c->fpu_id);
+	if (cpu_has_msa)
+		pr_info("MSA revision is: %08x\n", c->msa_id);
 }