powerpc: Use CONFIG_ARCH_HAS_FAST_MULTIPLIER

I ran some tests to compare hash_64 using shifts and multiplies.
The results:

POWER6:	~2x slower
POWER7: ~2x faster
POWER8: ~2x faster

Now we have a proper config option, select
CONFIG_ARCH_HAS_FAST_MULTIPLIER on POWER7 and POWER8.

Signed-off-by: Anton Blanchard <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>

diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 26703be24cf9da422d75129f5c4eb444207e4e60..35ae7ec392ec018bce8cc904fe30bacdbcb2089a 100644 (file)
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -116,10 +116,12 @@ config POWER6_CPU
 config POWER7_CPU
        bool "POWER7"
        depends on PPC_BOOK3S_64
+       select ARCH_HAS_FAST_MULTIPLIER
 
 config POWER8_CPU
        bool "POWER8"
        depends on PPC_BOOK3S_64
+       select ARCH_HAS_FAST_MULTIPLIER
 
 config E5500_CPU
        bool "Freescale e5500"