[Buildroot] [PATCH 1/3] arch: add support for mcf54418 Colfdire

[Jean-Michel Hautbois]

Hi Yann,

On 03/07/2023 20:55, Yann E. MORIN wrote:
> Jean-Michel, All,
> 
> On 2023-06-29 07:31 +0200, Jean-Michel Hautbois spake thusly:
>> The m68k family ony has one Coldfire variant, namely the 5208. Add the
>> support for the MCF54418 CPU in the configuration file.
> 
> As your cover-letter said, eda11417beaf (m68k: remove
> BR2_GCC_TARGET_ARCH), setting it breaks use of external toolchains.
> 
> Granted, the commit log was not very expansive in why it did break them
> which required dropping setting m68k/cf.

Indeed. Well, I did not found the root cause, but I can say for sure 
that the USE_MMU configuration makes it impossible to build the 
buildroot toolchain.

> However, it did state that the m68k/cf defconfigs where working
> perfectly well without it.
> 
> So, your commit log should explain how/why it is safe to re-introduce
> BR2_GCC_TARGET_ARCH. I see you only set ig for this new CPU variant, so
> maybe that's enough of a reason.
> 
> Still, it'd be nice to have it explained in plain letters.

OK, so get the content from the plain letter and have it in this commit 
message too ;-).

> Also, it'd be nice if you could try with an external toolchain, and
> explain that in the commit log. If you do not have an external toolchain
> available, you can generate one with Buildroot, and re-use it as an
> external toolchain.

Sadly, the only external toolchain I tried is the one from bootlin, and 
it is not compatible with a CPU which has a MMU. Considering I might 
miss some things !

JM
> 
> Regards,
> Yann E. MORIN.
> 
>> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at yoseli.org>
>> ---
>>   arch/Config.in.m68k | 9 +++++++++
>>   toolchain/Config.in | 1 +
>>   2 files changed, 10 insertions(+)
>>
>> diff --git a/arch/Config.in.m68k b/arch/Config.in.m68k
>> index 9fd22aaf1e..6aa409b272 100644
>> --- a/arch/Config.in.m68k
>> +++ b/arch/Config.in.m68k
>> @@ -33,11 +33,20 @@ config BR2_m68k_cf5208
>>   	select BR2_m68k_cf
>>   	select BR2_SOFT_FLOAT
>>   
>> +config BR2_m68k_cf54418
>> +	bool "54418"
>> +	select BR2_m68k_cf
>> +	select BR2_USE_MMU
>> +	select BR2_SOFT_FLOAT
>>   endchoice
>>   
>>   config BR2_GCC_TARGET_CPU
>>   	default "68040"		if BR2_m68k_68040
>>   	default "5208"		if BR2_m68k_cf5208
>> +	default "54455"		if BR2_m68k_cf54418
>> +
>> +config BR2_GCC_TARGET_ARCH
>> +	default "cf"            if BR2_m68k_cf54418
>>   
>>   config BR2_READELF_ARCH_NAME
>>   	default "MC68000"
>> diff --git a/toolchain/Config.in b/toolchain/Config.in
>> index ff0eb93017..ec2185cb39 100644
>> --- a/toolchain/Config.in
>> +++ b/toolchain/Config.in
>> @@ -95,6 +95,7 @@ config BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS
>>   	depends on !BR2_ARM_CPU_ARMV5
>>   	depends on !BR2_sparc_v8
>>   	depends on !BR2_m68k_cf5208
>> +	depends on !BR2_m68k_cf54418
>>   
>>   # GCC uses thunk functions to adjust the 'this' pointer when calling
>>   # C++ member functions in classes derived with multiple inheritance.
>> -- 
>> 2.39.2
>>
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>