[U-Boot] [PATCH v2 1/2] armv8: Support loading 32-bit OS in AArch32 execution state

[Alexander Graf <agraf@suse.de>]

On 20.05.16 10:26, Huan Wang wrote:
>> On 20.05.16 08:53, Huan Wang wrote:
>>>> On 05/19/2016 10:26 AM, Alison Wang wrote:
>>>>> To support loading a 32-bit OS, the execution state will change from
>>>>> AArch64 to AArch32 when jumping to kernel.
>>>>>
>>>>> The architecture information will be got through checking FIT image,
>>>>> then U-Boot will load 32-bit OS or 64-bit OS automatically.
>>>>>
>>>>> Signed-off-by: Ebony Zhu <ebony.zhu@nxp.com>
>>>>> Signed-off-by: Alison Wang <alison.wang@nxp.com>
>>>>> Signed-off-by: Chenhui Zhao <chenhui.zhao@nxp.com>
>>>>> ---

[...]

>>>>> --- a/common/image-fit.c
>>>>> +++ b/common/image-fit.c
>>>>> @@ -1163,7 +1163,8 @@ int fit_image_check_arch(const void *fit, int
>>>> noffset, uint8_t arch)
>>>>>   	if (fit_image_get_arch(fit, noffset, &image_arch))
>>>>>   		return 0;
>>>>>   	return (arch == image_arch) ||
>>>>> -		(arch == IH_ARCH_I386 && image_arch == IH_ARCH_X86_64);
>>>>> +		(arch == IH_ARCH_I386 && image_arch == IH_ARCH_X86_64) ||
>>>>> +		(arch == IH_ARCH_ARM64 && image_arch == IH_ARCH_ARM);
>>>>
>>>> This should be a Kconfig option. ThunderX doesn't support AArch32
>>>> execution.
>>> [Alison Wang] I can't understand your meaning. Can you clarify it?
>>
>> U-Boot supports the ThunderX SoC which uses Cavium's own ARMv8 core
>> implementation. That core does not support running AArch32 code.
>>
> [Alison Wang] Oh, I think your concern is that this function will not
> detect FIT image is wrong when loading 32-bit kernel on ThunderX, right?
> 
> Then what is your suggestion to fix this issue?

My suggestion is to introduce a new Kconfig option that says "this arm64
system can execute aarch32 code" which is set as default y.
CONFIG_THUNDERX would then set it to n if that's possible - or you'd
just set it to n in the thunderx defconfig.


Alex