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

[Huan Wang]

> 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 at nxp.com>
> >>>>> Signed-off-by: Alison Wang <alison.wang at nxp.com>
> >>>>> Signed-off-by: Chenhui Zhao <chenhui.zhao at 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.
[Alison Wang] Good idea. I will do it in the next version. Thanks.

Best Regards,
Alison Wang