Subject: Re: [PATCH v2 16/16] powerpc/microwatt: Don't select the hash MMU code

From: Nicholas Piggin <[email-masked]>
Date: Thu, 21 Oct 2021 17:38:51 +1000

Excerpts from Joel Stanley's message of October 21, 2021 3:19 pm:
> On Thu, 21 Oct 2021 at 04:04, Nicholas Piggin <[email-masked]> wrote:
>>
>> Microwatt is radix-only, so it does not require hash MMU support.
>>
>> This saves 20kB compressed dtbImage and 56kB vmlinux size.
>>
>> Signed-off-by: Nicholas Piggin <[email-masked]>
>> ---
>>  arch/powerpc/configs/microwatt_defconfig | 1 -
>>  arch/powerpc/platforms/microwatt/Kconfig | 1 -
>>  2 files changed, 2 deletions(-)
>>
>> diff --git a/arch/powerpc/configs/microwatt_defconfig b/arch/powerpc/configs/microwatt_defconfig
>> index 6e62966730d3..7c8eb29d8afe 100644
>> --- a/arch/powerpc/configs/microwatt_defconfig
>> +++ b/arch/powerpc/configs/microwatt_defconfig
>> @@ -27,7 +27,6 @@ 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
> 
> We still end up with CONFIG_PPC_64S_HASH_MMU=y in the config as it
> defaults to y.

If you make microwatt_defconfig? Hm, IIRC this came from savedefconfig 
after unselecting hash mmu so I'm not sure why that doesn't work.
> 
> We should disable in the defconfig it so your new changes are tested
> by that defconfig:
> 
> +# CONFIG_PPC_64S_HASH_MMU is not set
> 
> I boot tested your series on Microwatt with microwatt_defconfig (with
> and without that option set) and ppc64le_defconfig.

Nice.

Thanks,
Nick

> 
> Cheers,
> 
> Joel
> 
>> diff --git a/arch/powerpc/platforms/microwatt/Kconfig b/arch/powerpc/platforms/microwatt/Kconfig
>> index 823192e9d38a..5e320f49583a 100644
>> --- a/arch/powerpc/platforms/microwatt/Kconfig
>> +++ b/arch/powerpc/platforms/microwatt/Kconfig
>> @@ -5,7 +5,6 @@ config PPC_MICROWATT
>>         select PPC_XICS
>>         select PPC_ICS_NATIVE
>>         select PPC_ICP_NATIVE
>> -       select PPC_HASH_MMU_NATIVE if PPC_64S_HASH_MMU
>>         select PPC_UDBG_16550
>>         select ARCH_RANDOM
>>         help
>> --
>> 2.23.0
>>
>