[Letux-kernel] [OpenOCD-devel] [PATCH]: d86217d board: add Skytone Alpha 400

Paul Boddie paul at boddie.org.uk
Sat Oct 24 19:01:04 CEST 2020

On Saturday, 24 October 2020 16:26:43 CEST H. Nikolaus Schaller wrote:
> Hi Lubomir,
> The specific list was replaced by the letux-kernel devel mailing
> list because the kernel tree now covers a big set of different devices in
> parallel. So there was no need any more for device specific lists (at least
> on kernel level).

One problem with the general list is that there can be a lot of traffic that 
isn't particularly interesting to those of us with special interests. And it 
can be very oppressive to have to receive patch sequences over and over again 
for random hardware, which is a "feature" of a lot of Linux development lists.

But special interest lists can easily decline into unsustainable and isolated 
communities, and I do see the benefit of having the broader audience of a 
general list where people can potentially bring new insights to devices of 
which they have no direct experience.

> I have CCed the list plus two GNUsteppers from whom I know that they
> are still interested in MIPS and this machine.

Nice to know that some people are still interested in MIPS. Probably more so 
than the company that owns the technology these days. ;-)

> > Am 24.10.2020 um 15:35 schrieb Lubomir Rintel <lkundrak at v3.sk>:
> >
> > I've only recently got the machine and started to look around. I'd like
> > it to eventually run up to date software, notably mainline Linux.
> > I'm currently beating u-boot into shape and intend to try send out the
> > patches upstream soonish.
> > 
> > I've noticed that H. Nikolaus Schaller keeps rebasing his and Paul
> > Boddie's jz4730 patches in the letux-kernel tree [1].
> We try to do our best...


> > I've had to fix up quite some issues to get the thing to build so I
> > suspect they probably don't run it?
> Well, it is unfortunately on really low priority for me. I just would have
> to open my Letux 400 and solder a connector for the serial console and close
> the device again :) So that I can see what is happening during hand-over
> from U-Boot to the kernel or if the kernel isn't booting to at least some
> login: prompt.

My patches are rather tentative because (1) a lot of the work has been to just 
get things updated to work with "modern" practices, and (2) I have low 
expectations about things working until most of the pieces are in place. And 
even then, I have fairly low expectations because the Linux kernel isn't 
exactly the most testable thing, especially without a serial console.

> Unfortunately a lot of documentation about these devices has been lost.
> AFAIR there was Kwaak (some early public Wiki) and the wayback machine has
> archived some parts, but for example I could no longer find the photos
> about disassembly.

I am sure I have some pictures of the circuit board somewhere, although I just 
spent quite some time looking and didn't find them. Maybe David has those 

> Another problem is that I am no longer experienced in the details how to
> boot from SD card... AFAIR there was some special key combination and if
> one get it wrong the system will overwrite flash where only JTAG could
> recover the bricked device.

"Fn" and left "Shift" should boot from SD. I was using that to boot my L4Re 
payloads and didn't have any problems. That applies to the Letux 400, however, 
and I can't make any guarantees about other variants.

> A minor problem is that the remaining batteries are now all broken, but it
> works without, just with power supply.

Batteries are a real problem. I also have an Efika Smartbook whose battery no 
longer works. The lifespan and lifecycle of batteries should be a real 
concern, but everything seems to be "designed for disposal" regardless of how 
much or often it ends up being used.

> > My intent was to send the patches their way and ask about
> > the status of the tree; adding them to Cc now so they can chime in.
> Yes, please. Patches are always welcome!
> > [1] https://git.goldelico.com/?p=letux-kernel.git;a=heads
> > 
> >> I found a few years ago that the FCC registration document for the
> >> Skytone Alpha 400 (FCC ID WMGALPHA400) simply points to the Sungworld
> >> SW-E700 (FCC ID WI3SW-E700). The Sungworld FCC database entry has a
> >> schematic attached.
> > 
> > I've got the schematic from here [2]. It looks like it's probably the
> > same one.
> > 
> > 
> > [2] https://download.goldelico.com/letux-400/files/
> Hardware-wise these devices (Skytone, Elonex, Letux and many more) seem
> to be the same.

Let's not forget the documentation area, too:


I could probably add more details to that, given that there has been some 
effort to formulate how the hardware works in connection with modernising 
those patches.


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