[J-core] Is a small Linux distribution available for J2 on Numato Mimas?

[Abhishek Madhyastha]

Hi Rich,

What'd be your opinion on the Ethernet expansion board that Numato
provides(this was discussed a while ago on another mail chain)?

I mean, it wouldn't make sense for them to provide an expansion board
& use a Xilinx EDK made emac to talk to it if it would be this slow,
right?
,
What am I missing here? Is it the lack of an OS while using the
Microblaze to interface to the emac(& subsequently the phy on the
expansion board)?

-Abhishek

On 8/6/16, Rich Felker <dalias at libc.org> wrote:
> On Sat, Aug 06, 2016 at 05:50:20AM +0000, Brian Bartholomew wrote:
>> Has anyone compiled a small Linux distribution for J2 on the Numato
>> Mimas?  By "small" I mean has emacs and can build packages natively,
>> but doesn't have X-Windows.
>
> A native toolchain takes about 15 seconds to compile and link a hello
> world application, after the toolchain binaries have been executed
> once and cached in ram, so while it's possible a native toolchain is
> not very practical. This is largely a consequence of the FPGA running
> at just 50 MHz, and probably also the small (8k) icache and dcache
> size.
>
> I'm pretty sure emacs is not nommu-compatible due to the "dumper"
> architecture, which depends on being loaded at the same logical
> (=physical, for nommu) address it was running at when it was dumped.
> Emacs can be built without the dumper, but then it takes 30 seconds to
> load its elisp on a 1.5 GHz x86. On J2 I would expect it to take
> several hours to load like that. A J3 with mmu would overcome this
> issue.
>
> Other editors should work reasonably well. I know I've used nano, and
> it's smooth for typing within a line, but feels noticably slow for
> inserting/removing lines. This is probably due to a largeish memmove
> in nano or in ncurses.
>
> In terms of actual distributions, Rob has a build script at
> https://github.com/j-core/mkroot that can produce just a minimal
> working userspace, and Buildroot can be convinced to target J2
> reasonably well if you give it an external toolchain. Getting
> better/native support upstream in Buildroot is an ongoing goal.
> OpenEmbedded might also work; I'm not sure. With anything much bigger
> than that, I don't think you'll find distros where anyone has put any
> thought into supporting nommu, so you'll have better luck once there's
> a J3.
>
> Rich
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