[OpenWrt-Devel] Hard float ABI for BCM2708/BCM2709

[Matthias Schiffer]

On 07/11/2015 07:21 PM, Florian Fainelli wrote:
> Le 11 juil. 2015 09:52, "Matthias Schiffer" <mschiffer at universe-factory.net>
> a écrit :
>>
>> Hi,
>> I've noticed that OpenWrt currently uses the soft-float ABI in the
>> Raspberry Pi images. Is there a specific reason hard float is not used,
>> even though most other distributions like Raspbian have switched to it?
> 
> I do not think there was any particular reason. This was one of the few
> ARM-based targets that are not armv5, however armv5 may have been used as a
> template to kick the initial port.
> 
>>
>> I tried adding "fpu" to FEATURES to enable hard-float, and the generated
>> images seem to work fine.
> 
> If you want to submit a patch doing this, I will gladly apply it, we may
> have to set a different FPU ABI between brcm2708 and 09 though.
> --
> Florian
> 

Okay, I'll do some more tests on both brcm2708 and 09 and prepare a patch.

I've noticed that currently the toolchain directory naming is somewhat
broken in regard to FP ABIs: the 'fpu' FEATURES flag affects the flags
the toolchain is built with (--with-float=soft), but this difference
isn't reflected in the directory name. I currently see two ways to fix this:

1. Add a 'fpu' or 'softfp' suffix to the directory name (as it is done
with 'spe')
2. Don't configure fpu in FEATURES, but make the value of CONFIG_HAS_FPU
depend on CPU_TYPE/CPU_SUBTYPE. Can it ever happen that we need the same
CPU_TYPE/CPU_SUBTYPE combination both with and without HAS_FPU? I see
the flag has been introduced in r11337 by kaloz.

Or even both, so the directory suffix will be adjusted accordingly when
CONFIG_SOFT_FLOAT is changed manually.

Matthias

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