ARMv7: Correctly identify the CPU architecture version

The cpu_architecture() function in arch/arm/kernel/setup.c only works
with cores produced by ARM Ltd. The more generic approach is to read
the ID_MMFR0 register and check for the VMSA or PMSA version
supported.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm/kernel/setup.c

@@ -301,10 +301,23 @@ int cpu_architecture(void)
 		cpu_arch = (processor_id >> 16) & 7;
 		if (cpu_arch)
 			cpu_arch += CPU_ARCH_ARMv3;
-	} else {
-		/* the revised CPUID */
-		cpu_arch = ((processor_id >> 12) & 0xf) - 0xb + CPU_ARCH_ARMv6;
-	}
+	} else if ((processor_id & 0x000f0000) == 0x000f0000) {
+		unsigned int mmfr0;
+
+		/* Revised CPUID format. Read the Memory Model Feature
+		 * Register 0 and check for VMSAv7 or PMSAv7 */
+		asm("mrc	p15, 0, %0, c0, c1, 4"
+		    : "=r" (mmfr0));
+		if ((mmfr0 & 0x0000000f) == 0x00000003 ||
+		    (mmfr0 & 0x000000f0) == 0x00000030)
+			cpu_arch = CPU_ARCH_ARMv7;
+		else if ((mmfr0 & 0x0000000f) == 0x00000002 ||
+			 (mmfr0 & 0x000000f0) == 0x00000020)
+			cpu_arch = CPU_ARCH_ARMv6;
+		else
+			cpu_arch = CPU_ARCH_UNKNOWN;
+	} else
+		cpu_arch = CPU_ARCH_UNKNOWN;
 
 	return cpu_arch;
 }