[PATCH] ARM: PJ4: allow building in Thumb-2 mode

[Ard Biesheuvel]

On 25 November 2014 at 17:14, Gregory CLEMENT
<gregory.clement at free-electrons.com> wrote:
> On 24/11/2014 20:49, Ard Biesheuvel wrote:
>> On 24 November 2014 at 20:01, Gregory CLEMENT
>> <gregory.clement at free-electrons.com> wrote:
>>> On 24/11/2014 18:48, Ard Biesheuvel wrote:
>>>> On 24 November 2014 at 18:36, Gregory CLEMENT
>>>> <gregory.clement at free-electrons.com> wrote:
>>>>> Hi Arnd,
>>>>>
>>>>> On 24/11/2014 18:17, Arnd Bergmann wrote:
>>>>>> On Monday 24 November 2014 16:34:47 Ard Biesheuvel wrote:
>>>>>>> On 24 November 2014 at 16:29, Arnd Bergmann <arnd at arndb.de> wrote:
>>>>>>>> On Monday 24 November 2014 12:56:40 Ard Biesheuvel wrote:
>>>>>>>>> Two files that get included when building the multi_v7_defconfig target
>>>>>>>>> fail to build when selecting THUMB2_KERNEL for this configuration.
>>>>>>>>>
>>>>>>>>> In both cases, we can just build the file as ARM code, as none of its
>>>>>>>>> symbols are exported to modules, so there are no interworking concerns.
>>>>>>>>> In the iwmmxt.S case, add ENDPROC() declarations so the symbols are
>>>>>>>>> annotated as functions, resulting in the linker to emit the appropriate
>>>>>>>>> mode switches.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>>>>>>>>
>>>>>>>> Ah, very nice. I tried this before, but my version didn't actually
>>>>>>>> work, presumably because I didn't know about the ENDPROC() stuff.
>>>>>>>>
>>>>>>>> Have you tested this on a machine that has IWMMXT enabled?
>>>>>>>>
>>>>>>>
>>>>>>> No, I don't have access to such a machine, unfortunately.
>>>>>>
>>>>>> Adding a few mvebu folks to Cc, maybe one of them can test your patch.
>>>>>
>>>>> Actually even it is a feature of the PJ4 machine non of the mvebu machines
>>>>> currently use it. I only see this configuration enabled for the pxa family.
>>>>> So I think you would have more feedback with the pxa maintainers/owners.
>>>>>
>>>>
>>>> Are you saying PJ4 should be dropped from 'default' here?
>>>
>>> Not at all. I didn't find it in the configuration file, but I didn't realized
>>> it was because of this "default y".
>>>
>>> Sorry for the noise.
>>>
>>
>> Ah, ok.
>>
>> In that case, could you perhaps also test this patch on a PJ4 machine
>> with multi_v7_defconfig but with CONFIG_THUMB2_KERNEL enabled?
>
> Actually as explained in the commit "ARM: 8040/1: pj4: properly detect
> existence of the iWMMXt co-processor", the Armada 370 and Armada XP have
> a PJ4B CPU without the iWMMXt extension. The only boards I have using CPus
> belonging to the PJ4 family use these SoCs so I wasn't able to fully
> tested it. At least I can say that these SoC are now buildable in Thumb
> mode with this patch and I didn't see any regression while booting the
> system compiled in Thumb2.
>

OK. If the iWMMXt code is never actually called, testing on such a SoC
doesn't make a lot of sense
But Olof's test should be sufficient.

Thanks,
Ard.