[PATCH 1/2] armv8: aarch32: Execute 32-bit Linux for LayerScape platforms

Robin Murphy
2016-09-23T13:18:31Z

On 23/09/16 14:13, Stuart Yoder wrote:
>
>
>> -----Original Message-----
>> From: Robin Murphy [mailto:robin.murphy at arm.com]
>> Sent: Friday, September 23, 2016 7:17 AM
>> To: Alison Wang <b18965@freescale.com>; shawnguo at kernel.org; kernel at pengutronix.de; Fabio Estevam
>> Estevam <fabio.estevam@nxp.com>; linux at armlinux.org.uk; linux-arm-kernel at lists.infradead.org; linux-
>> kernel at vger.kernel.org; Scott Wood <scott.wood@nxp.com>; Stuart Yoder <stuart.yoder@nxp.com>; Leo Li
>> <leoyang.li@nxp.com>
>> Cc: Jason Jin <jason.jin@nxp.com>
>> Subject: Re: [PATCH 1/2] armv8: aarch32: Execute 32-bit Linux for LayerScape platforms
>>
>> Hi Alison,
>>
>> On 23/09/16 03:19, Alison Wang wrote:
>>> The ARMv8 architecture supports:
>>> 1. 64-bit execution state, AArch64.
>>> 2. 32-bit execution state, AArch32, that is compatible with previous
>>> versions of the ARM architecture.
>>>
>>> LayerScape platforms are compliant with ARMv8 architecture. This patch
>>> is to support running 32-bit Linux kernel for LayerScape platforms.
>>>
>>> Verified on LayerScape LS1043ARDB, LS1012ARDB, LS1046ARDB boards.
>>>
>>> Signed-off-by: Ebony Zhu <ebony.zhu@nxp.com>
>>> Signed-off-by: Alison Wang <alison.wang@nxp.com>
>>> ---
>>> arch/arm/Kconfig | 9 +++++++++
>>> arch/arm/mach-imx/Kconfig | 14 ++++++++++++++
>>> arch/arm/mach-imx/Makefile | 4 +++-
>>> arch/arm/mach-imx/mach-layerscape.c | 23 +++++++++++++++++++++++
>>> 4 files changed, 49 insertions(+), 1 deletion(-)
>>> create mode 100644 arch/arm/mach-imx/mach-layerscape.c
>>>
>>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>>> index f0c8068..e8d470e 100644
>>> --- a/arch/arm/Kconfig
>>> +++ b/arch/arm/Kconfig
>>> @@ -294,6 +294,15 @@ config PGTABLE_LEVELS
>>> default 3 if ARM_LPAE
>>> default 2
>>>
>>> +config ARCH_AARCH32_ES_SUPPORT
>>> + def_bool n
>>> + help
>>> + The ARMv8 architecture supports 64-bit execution state, AArch64
>>> + and 32-bit execution state, AArch32, that is compatible with
>>> + previous versions of the ARM architecture.
>>> +
>>> + Enable AArch32 execution state support for ARMv8 architecture.
>>
>> What's this supposed to do, exactly? I've been running 32-bit kernels on
>> my Juno with very little issue (beyond a couple of DT tweaks, and some
>> firmware hacks with a corresponding bit of A64 assembly tacked on the
>> front of the zImage to switch into AArch32 state).
>
> Which arch/arm/mach-* platform are you using for Juno?

I don't even know! :) I just start with a multi_v7_defconfig plus a few
extra bits (LPAE, KVM, sil24, sky2, etc.) and it works. I guess it's the
combination of mach-vexpress and mach-virt.

Robin.

>
> Thanks,
> Stuart
>