[PATCH 0/4] arm/versatile: no-MMU support

[Greg Ungerer]

Hi Vladimir,

On 08/12/16 00:27, Vladimir Murzin wrote:
> Hi Greg,
>
> On 07/12/16 14:21, Greg Ungerer wrote:
>> Hi Vladimir,
>>
>> On 07/12/16 23:57, Greg Ungerer wrote:
>>> On 07/12/16 19:23, Vladimir Murzin wrote:
>>>> On 07/12/16 06:08, Greg Ungerer wrote:
>>>>> Does the ARM Versatile machine have a maintainer?
>>>>> I have CC'ed this patch set to those names reported by get_maintainer.
>>>>> I had no feedback on the first posting of this series back in August.
>>>>>
>>>>> The following patches support configuring and building the versatile
>>>>> machine with a no-MMU kernel.
>>>>>
>>>>> There is only a few minor changes required. It was previously possible
>>>>> in older kernels to build for versatile with CONFIG_MMU disabled, but
>>>>> the change to devicetree lost that capability. These changes make it
>>>>> possible again.
>>>>>
>>>>> One patch is a fix for address translation (broken in older kernels
>>>>> too),
>>>>> two are build problems when CONFIG_MMU is disabled, and the last is the
>>>>> actuall configuration changes needed.
>>>>>
>>>>> The motivation for this is that the versatile machine is well supported
>>>>> in qemu. And this provides an excellent platform for development and
>>>>> testing no-MMU support on ARM in general. With these patches applied
>>>>> it is possible to build and run a kernel with MMU disabled on qemu.
>>>>
>>>> I'm wondering if my "Allow NOMMU for MULTIPLATFORM" series [1] work
>>>> for you?
>>>>
>>>> [1] https://www.spinics.net/lists/arm-kernel/msg546823.html
>>>
>>> Sorry I hadn't seen these patches before.
>>>
>>> Just tried them out. With CONFIG_EXPERT set I can select and
>>> build for the Versatile machine with CONFIG_MMU not set. The
>>> build is successful, but the resulting kernel doesn't boot.
>>>
>>> I see that the resulting .config has CONFIG_PLAT_VERSATILE set
>>> but not CONFIG_ARCH_VERSATILE. Is this intentional?
>>
>> Let me revise that. By setting the "Multiple platform selection"
>> selection correctly to v5 platforms I did get CONFIG_ARCH_VERSATILE
>> set, and could still successfully build the kernel.
>>
>> A couple of other config options I had to readjust and I can
>> boot up this kernel under qemu. So success!
>>
>
> Congrats!!!
>
> Thanks for trying these patches! It is really nice to see someone else shows
> interest on NOMMU! If you don't mind I'll keep you in Cc when/if I re-spin my
> patches ;)

Yes, please do.

Regards
Greg


> Cheers
> Vladimir
>
>>
>>> With CONFIG_ARCH_VERSATILE missing the build doesn't traverse
>>> into arch/arm/mach-versatile, and you don't get any device tree
>>> built.
>>>
>>> Ultimately to produce a working kernel we will still need my
>>> patch 01/04 ("ARM: versatile: support no-MMU mode addressing").
>>> No surprise here, this was missing in older kernels too.
>>
>> So in the end this is the only extra change I needed as well
>> to get the running kernel.
>>
>> Regards
>> Greg
>>
>>
>>
>
>