[linuxsh-dev] Re: [linux-sh:01551] Question: a good platform using SH-4 7750

[Mitch D. <md...@po...>]

ale wrote:
> 
>  I'm new to this community.

Hi Dong-In,

> I want to know what kind of board or PDA or anthing else is good for running
> LinuxSH.
> I read Mr. Kojima is using MS7750SE01 evaluation board.
> It seems that he is runnig stable GNU/Linux on the board.
> I could find only SH7750 HARP CPU board from Hitachi home page.
> Are MS7750SE01 board and SH7750 HARP CPU board same?

I have had experience with three SuperH boards.  The
first was a board with an SH3 that was designed in-house
when I worked for HP.  The second was the MS7750SE01 board.
The third is this unit, which we have ported full Linux to:

  http://www.pocketpenguins.com/IDA150specs.html

(It's much bigger than the picture would suggest - about A4 size,
and it's rated to be dropped 4 feet onto concrete.  We've done so
many times.  People get very very frightened when they see this
demonstration!!)

> How much overhead do you think to port Linux on that?

We have found it is quite quick to port the core kernel to a
new board, if you can get the bootloader working, and you have
technical information about the board.

It took us several weeks of futzing with the MS7750SE01 to get
the core working.  A lot of this was trying to get the Hitachi
HIMON to do anything sane.

> How much overhead do you think to port/write bootloader? Is there any
> 'reference' bootloader code to hack?

If you have a bare-bones (ie, not WinCE) machine, you can't go
past "sh-ipl+g", by Niibe Yutaka.  (To decode the acronym, that's
"SuperH Initial Program Loader, with Gdb stub").  To convert for
your board, you have to put in the BSC settings and tweak some
other things, then somehow get it into your board.  Then you can
use this and GDB to download kernel images.  Very very useful.
For source, have a look at the top of Niibe-san's page:

  http://www.m17n.org/linux-sh/index.html

When we ported Linux to the IDA, my colleague and I knew a lot
more about what we were doing.  It took us three days to discover
how awful the built-in monitor is, to hack a workaround, and to
port sh-ipl+g.  Then it only took three days to get the Linux
core working to the point where it was looking for a ramdisk
image.  One day after that, we had a user-mode program working.

I think it's really incredible that it's possible to get such
quick results on a new platform.  There are many others who
have contributed, but in particular, our success owes a lot
to Niibe-san for being the driving force behind the first port
to SuperH, and to Kaz Kojima, for some most extraordinary hacking
of the GNU toolchain so we can turn source into object code!
Thank you guys.

Regarding kernel hacking, most of the time since then (many
man-months) has been writing device-specific drivers, for
things like PCMCIA, touch screen, LCD, battery and power
management, status leds, front-panel keys, etc, etc.  That's
the bit that takes the time!! :-)

Anyway, hope this has helped.

Regards,

Mitch.
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