[Letux-kernel] [Lenny400] L4Re/Fiasco.OC on the Letux 400

H. Nikolaus Schaller hns at goldelico.com
Tue Apr 17 21:34:32 CEST 2018


Hi Paul,

> Am 17.04.2018 um 00:08 schrieb Paul Boddie <paul at boddie.org.uk>:
> 
> Hello,
> 
> I haven't been able to direct any real attention to the Letux 400 for quite 
> some time, but recently I managed to port the L4 Runtime Environment and 
> Fiasco.OC microkernel to the Ben NanoNote, most of the work already having 
> been done by the L4Re/Fiasco.OC developers and some people who ported these 
> things to the MIPS architecture.
> 
> Here is a summary of that work, with a collection of articles for anyone 
> *really* interested in the details:
> 
> https://blogs.fsfe.org/pboddie/?p=2147
> 
> Having done this, it did occur to me that I could give the Letux 400 some 
> attention in this regard. As everyone reading this will know, the Ben uses the 
> JZ4720 (a JZ4740 variant) whereas the Letux uses the mysterious JZ4730. But 
> since we gained some experience with "modernising" Linux support, David with 
> his "evolved" kernel and myself with some attempts to test functionality 
> within the old kernel and then in making a tentative modern kernel (which I 
> still haven't tested)

same for me... I just keep rebasing it on latest upstream release-candidates.
And doing a test compilation.

What I didn't find time for was to open the L400 and solder a connector
for access to the serial console. This seems to be the first step before
testing anything. Even if the device boots the very old kernel from flash.

> , it seemed reasonable to see what could be done.
> 
> To keep this message short, I can report that I did indeed get Fiasco.OC to 
> boot on the Letux, and I have written L4Re support for the CPM (clock and 
> power management), GPIO, LCD and PWM peripherals. The LCD support works within 
> the driver framework used by the framebuffer driver, and so framebuffer 
> programs can apparently just use the display without any special effort.
> 
> I have made my patches against the L4Re/Fiasco.OC repository available here:
> 
> http://www.boddie.org.uk/paul/L4Re-Fiasco.OC.html
> 
> You may wonder what this has to do with these lists, particularly the lenny400 
> list, which is largely concerned with Debian root filesystems and suitable 
> Linux kernels. And until I send this, I don't even know if the mipsbook-devel 
> list is even functioning any more.

As you indicate it is important to know that your kernel patches can not
be completely wrong :) So it is another stimulus to finally try to boot.

> 
> I would like to think that this opens another door to modern software 
> offerings for the Letux 400, even though work is needed to provide support for 
> other aspects of the hardware and to construct a suitable software framework 
> for "normal" use of the device. I intend to investigate things like Genode for 
> the latter task:
> 
> http://genode.org/
> 
> Meanwhile, I think that these technologies are also relevant for other Letux 
> products. It might be interesting to consider running something like QtMoko on 
> top of a software framework rooted in these technologies. Qt is apparently 
> supported by Genode, and so it might not be so absurd to consider a relatively 
> lightweight environment combining the two.

Oh, that would be an interesting task. What I don't know is if the current
QtMoko has any hard coded focus on armhf. So switching to mipsel (soft-float)
may be easy or may not...

> 
> Anyway, I hope this is of interest to someone out there!

Yes, definitively.

BR and thanks for sharing,
Nikolaus



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