MIPS: Support for targetting MIPSr6

Add support for targetting MIPS32r6 & MIPS64r6 systems, in the same way
that we currently select release 1 or release 2 targets. MIPSr6 is not
entirely backwards compatible with earlier releases of the architecture.
Some instructions are encoded differently, some are removed, some are
reused, so it is not practical to run U-Boot built for earlier revisions
on a MIPSr6 system. Update their Kconfig help text to reflect that.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>

arch/mips/Kconfig

@@ -104,7 +104,7 @@ config CPU_MIPS32_R1
 	depends on SUPPORTS_CPU_MIPS32_R1
 	select 32BIT
 	help
-	  Choose this option to build an U-Boot for release 1 or later of the
+	  Choose this option to build an U-Boot for release 1 through 5 of the
 	  MIPS32 architecture.
 
 config CPU_MIPS32_R2
@@ -112,7 +112,15 @@ config CPU_MIPS32_R2
 	depends on SUPPORTS_CPU_MIPS32_R2
 	select 32BIT
 	help
-	  Choose this option to build an U-Boot for release 2 or later of the
+	  Choose this option to build an U-Boot for release 2 through 5 of the
+	  MIPS32 architecture.
+
+config CPU_MIPS32_R6
+	bool "MIPS32 Release 6"
+	depends on SUPPORTS_CPU_MIPS32_R6
+	select 32BIT
+	help
+	  Choose this option to build an U-Boot for release 6 or later of the
 	  MIPS32 architecture.
 
 config CPU_MIPS64_R1
@@ -120,7 +128,7 @@ config CPU_MIPS64_R1
 	depends on SUPPORTS_CPU_MIPS64_R1
 	select 64BIT
 	help
-	  Choose this option to build a kernel for release 1 or later of the
+	  Choose this option to build a kernel for release 1 through 5 of the
 	  MIPS64 architecture.
 
 config CPU_MIPS64_R2
@@ -128,7 +136,15 @@ config CPU_MIPS64_R2
 	depends on SUPPORTS_CPU_MIPS64_R2
 	select 64BIT
 	help
-	  Choose this option to build a kernel for release 2 or later of the
+	  Choose this option to build a kernel for release 2 through 5 of the
+	  MIPS64 architecture.
+
+config CPU_MIPS64_R6
+	bool "MIPS64 Release 6"
+	depends on SUPPORTS_CPU_MIPS64_R6
+	select 64BIT
+	help
+	  Choose this option to build a kernel for release 6 or later of the
 	  MIPS64 architecture.
 
 endchoice
@@ -175,19 +191,25 @@ config SUPPORTS_CPU_MIPS32_R1
 config SUPPORTS_CPU_MIPS32_R2
 	bool
 
+config SUPPORTS_CPU_MIPS32_R6
+	bool
+
 config SUPPORTS_CPU_MIPS64_R1
 	bool
 
 config SUPPORTS_CPU_MIPS64_R2
 	bool
 
+config SUPPORTS_CPU_MIPS64_R6
+	bool
+
 config CPU_MIPS32
 	bool
-	default y if CPU_MIPS32_R1 || CPU_MIPS32_R2
+	default y if CPU_MIPS32_R1 || CPU_MIPS32_R2 || CPU_MIPS32_R6
 
 config CPU_MIPS64
 	bool
-	default y if CPU_MIPS64_R1 || CPU_MIPS64_R2
+	default y if CPU_MIPS64_R1 || CPU_MIPS64_R2 || CPU_MIPS64_R6
 
 config MIPS_TUNE_4KC
 	bool

arch/mips/Makefile

@@ -19,8 +19,10 @@ PLATFORM_CPPFLAGS += $(patsubst %,-I$(srctree)/%include,$(machdirs))
 # Optimize for MIPS architectures
 arch-$(CONFIG_CPU_MIPS32_R1) += -march=mips32 -Wa,-mips32
 arch-$(CONFIG_CPU_MIPS32_R2) += -march=mips32r2 -Wa,-mips32r2
+arch-$(CONFIG_CPU_MIPS32_R6) += -march=mips32r6 -Wa,-mips32r6
 arch-$(CONFIG_CPU_MIPS64_R1) += -march=mips64 -Wa,-mips64
 arch-$(CONFIG_CPU_MIPS64_R2) += -march=mips64r2 -Wa,-mips64r2
+arch-$(CONFIG_CPU_MIPS64_R6) += -march=mips64r6 -Wa,-mips64r6
 
 # Allow extra optimization for specific CPUs/SoCs
 tune-$(CONFIG_MIPS_TUNE_4KC) += -mtune=4kc