powerpc/64s: update cpu selection options

Update the 64s GENERIC_CPU option. POWER4 support has been dropped, so
make that clear in the option name. The POWER5_CPU option is dropped
because it's uncommon, and GENERIC_CPU covers it.

-mtune= before power8 is dropped because the minimum gcc version
supports power8, and tuning is made consistent between big and little
endian.

A 970 option is added for PowerPC 970 / G5 because they still have a
user base, and -mtune=power8 does not generate good code for the 970.

This also updates the ISA versions document to add Power4/Power4+
because I didn't realise Power4+ used 2.01.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220921014103.587954-2-npiggin@gmail.com

Documentation/powerpc/isa-versions.rst

@@ -4,6 +4,8 @@ CPU to ISA Version Mapping
 
 Mapping of some CPU versions to relevant ISA versions.
 
+Note Power4 and Power4+ are not supported.
+
 ========= ====================================================================
 CPU       Architecture version
 ========= ====================================================================
@@ -26,6 +28,12 @@ PPC970    - PowerPC User Instruction Set Architecture Book I v2.01
           - PowerPC Virtual Environment Architecture Book II v2.01
           - PowerPC Operating Environment Architecture Book III v2.01
           - Plus Altivec/VMX ~= 2.03
+Power4+   - PowerPC User Instruction Set Architecture Book I v2.01
+          - PowerPC Virtual Environment Architecture Book II v2.01
+          - PowerPC Operating Environment Architecture Book III v2.01
+Power4    - PowerPC User Instruction Set Architecture Book I v2.00
+          - PowerPC Virtual Environment Architecture Book II v2.00
+          - PowerPC Operating Environment Architecture Book III v2.00
 ========= ====================================================================
 
 
@@ -48,6 +56,8 @@ Power5++   No
 Power5+    No
 Power5     No
 PPC970     Yes
+Power4+    No
+Power4     No
 ========== ==================
 
 ========== ====
@@ -66,6 +76,8 @@ Power5++   No
 Power5+    No
 Power5     No
 PPC970     No
+Power4+    No
+Power4     No
 ========== ====
 
 ========== ====================================
@@ -84,4 +96,6 @@ Power5++   No
 Power5+    No
 Power5     No
 PPC970     No
+Power4+    No
+Power4     No
 ========== ====================================

arch/powerpc/Makefile

@@ -149,11 +149,12 @@ CFLAGS-$(CONFIG_PPC32)	+= $(call cc-option,-mno-readonly-in-sdata)
 ifdef CONFIG_PPC_BOOK3S_64
 ifdef CONFIG_CPU_LITTLE_ENDIAN
 CFLAGS-$(CONFIG_GENERIC_CPU) += -mcpu=power8
-CFLAGS-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=power9,-mtune=power8)
 else
-CFLAGS-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=power7,$(call cc-option,-mtune=power5))
 CFLAGS-$(CONFIG_GENERIC_CPU) += -mcpu=power4
 endif
+CFLAGS-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=power10,	\
+				  $(call cc-option,-mtune=power9,	\
+				  $(call cc-option,-mtune=power8)))
 else ifdef CONFIG_PPC_BOOK3E_64
 CFLAGS-$(CONFIG_GENERIC_CPU) += -mcpu=powerpc64
 endif

arch/powerpc/platforms/Kconfig.cputype

@@ -126,7 +126,7 @@ choice
 	  If unsure, select Generic.
 
 config GENERIC_CPU
-	bool "Generic (POWER4 and above)"
+	bool "Generic (POWER5 and PowerPC 970 and above)"
 	depends on PPC_BOOK3S_64 && !CPU_LITTLE_ENDIAN
 	select PPC_64S_HASH_MMU
 
@@ -145,8 +145,8 @@ config CELL_CPU
 	depends on PPC_BOOK3S_64 && !CPU_LITTLE_ENDIAN
 	select PPC_64S_HASH_MMU
 
-config POWER5_CPU
-	bool "POWER5"
+config PPC_970_CPU
+	bool "PowerPC 970 (including PowerPC G5)"
 	depends on PPC_BOOK3S_64 && !CPU_LITTLE_ENDIAN
 	select PPC_64S_HASH_MMU
 
@@ -235,7 +235,7 @@ config TARGET_CPU
 	string
 	depends on TARGET_CPU_BOOL
 	default "cell" if CELL_CPU
-	default "power5" if POWER5_CPU
+	default "970" if PPC_970_CPU
 	default "power6" if POWER6_CPU
 	default "power7" if POWER7_CPU
 	default "power8" if POWER8_CPU