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

[Greg Ungerer]

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!


> 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