Re: [RFC PATCH 6/6] powerpc/microwatt: Stop building the hash MMU code

Excerpts from Michael Ellerman's message of August 30, 2021 1:24 pm:

Christophe Leroy [off-list ref] writes:

quoted

Le 27/08/2021 à 18:34, Nicholas Piggin a écrit :

quoted

Microwatt is radix-only, so stop selecting the hash MMU code.

This saves 20kB compressed dtbImage and 56kB vmlinux size.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
  arch/powerpc/configs/microwatt_defconfig | 1 -
  arch/powerpc/platforms/Kconfig.cputype   | 1 +
  arch/powerpc/platforms/microwatt/Kconfig | 1 -
  3 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/configs/microwatt_defconfig b/arch/powerpc/configs/microwatt_defconfig
index bf5f2e5905eb..6fbad42f9e3d 100644
--- a/arch/powerpc/configs/microwatt_defconfig
+++ b/arch/powerpc/configs/microwatt_defconfig

@@ -26,7 +26,6 @@ CONFIG_PPC_MICROWATT=y
  # CONFIG_PPC_OF_BOOT_TRAMPOLINE is not set
  CONFIG_CPU_FREQ=y
  CONFIG_HZ_100=y
-# CONFIG_PPC_MEM_KEYS is not set
  # CONFIG_SECCOMP is not set
  # CONFIG_MQ_IOSCHED_KYBER is not set
  # CONFIG_COREDUMP is not set

diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 9b90fc501ed4..b9acd6c68c81 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype

@@ -371,6 +371,7 @@ config SPE
  config PPC_64S_HASH_MMU
  	bool "Hash MMU Support"
  	depends on PPC_BOOK3S_64
+	depends on !PPC_MICROWATT

Do we really want to start nit picking which platforms can select such or such option ?
Isn't it enough to get it off through the defconfig ?

Is PPC_MICROWATT mutually exclusive with other book3s64 configs ? Don't we build multiplatform kernels ?

Yeah that belongs in the microwatt defconfig, not as a forced exclusion
in Kconfig.

Okay I'll fix that up. In that case the select POWER9 should not be in 
Kconfig but just defconfig too. Which is fine, it just means oldconfig
won't change it.

Thanks,
Nick