[RFC v3 PATCH 00/25] Allow NOMMU for MULTIPLATFORM

Hi,

On 12/12/16 07:07, mickael guene wrote:

Hi all,

 You can find an R toolchain here:
https://github.com/mickael-guene/fdpic_manifest/releases/download/v7-r-1.0.1/toolset-v7-r-1.0.1-0-gbdcc6a7c-armv7-r.tgz

 It's an fdpic toolset for cortex-r cpu class. gcc version is
quite old (4.7).

 Note also that generated code may crash on class A cpu due to
generation of udiv/sdiv which is optional for class A.
(cortex a15 is ok but not a9).

Hope it helps

Unfortunately, it doesn't help because it depends on FDPIC Linux patches
which are out of tree and no link has been given.

M-class toolchain should just work with A-class; you don't even need to
disable MMU to try it out after d782e42 ("ARM: 8594/1: enable binfmt_flat on
systems with an MMU").

Cheers
Vladimir

Regards
Mickael

On 12/11/2016 09:01 PM, Peter Korsgaard wrote:

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"Afzal" == Afzal Mohammed [off-list ref] writes:

Hi,

 >> You can build a toolchain and initramfs with Buildroot. Have a look at
 >> the stm32f429 nommu config:
 >>
 >> https://git.buildroot.net/buildroot/tree/configs/stm32f429_disco_defconfig

 > iiuc, it builds one for Cortex-M. i already had a file system w/
 > busybox compiled using a Cortex-M toolchain (stolen from
 > Pengutronix's OSELAS.Toolchain), which works on Cortex M4 (Vybrid
 > VF610 M4 core). But it does not work here, i.e. on Cortex A, seems the
 > above mentioned also would have the same effect.

Hmm, I'm not sure why a cortex-M toolchain wouldn't work on cortex-A, I
thought the 'M' instruction set was a pure subset of the 'A'.

 > And in buildroot, couldn't see Cortex R option in menuconfig, and
 > selecting Cortex-A's excludes flat binary target & presents only with
 > ELF.

We indeed don't have cortex-R support. I'm not aware of any cortex-R
Linux support.

When you select a cortex-A variant, then we enable MMU support by
default, but you can disable it under toolchain options (Enable MMU) and
then the flat binary option is available.