Pb1500 and PCMCIA booting?

Pb1500 and PCMCIA booting?

[Greg Herlein]

Does anyone have advice/experience in what's the best way to get 
linux booting from the Pb1500 development board directly off 
PCMCIA?  I'm susepcting that getting a bootable filesystem rigged 
up on a CF card and using my handy CF <-> PCMCIA adapter card to 
get it onto the bus.  

Any advice/gotchas/hints as I start down this path?

Thanks in advance,

Greg

Re: Pb1500 and PCMCIA booting?

[Pete Popov]

Greg,

On Mon, 2003-10-27 at 11:15, Greg Herlein wrote:
> Does anyone have advice/experience in what's the best way to get 
> linux booting from the Pb1500 development board directly off 
> PCMCIA?  I'm susepcting that getting a bootable filesystem rigged 
> up on a CF card and using my handy CF <-> PCMCIA adapter card to 
> get it onto the bus.  
> 
> Any advice/gotchas/hints as I start down this path?

If you want to boot Linux off pcmcia, you need to add that support to
yamon or whatever boot code you're using.

If you're talking about using a pcmcia for a root file system, then what
you can do is:

- build your root fs and dump it on the pcmcia card
- create a small ramdisk which you'll statically link into your kernel.
Your ramdisk will be your temporary root FS and should contain on it
things like the pcmcia modules and socket driver, a script that loads
them, cardmgr, insmod, mount, and ... I don't remember what else but
that's pretty much it. The kernel mounts the ramdisk root fs, executes
your script which does its magic, then control is passed to the kernel
which mounts the real root fs on the pcmcia card.

Pete

Re: Pb1500 and PCMCIA booting?

[Dan Malek]

Greg Herlein wrote:

> Does anyone have advice/experience in what's the best way to get 
> linux booting from the Pb1500 development board directly off 
> PCMCIA?

Yes, but actually getting something to boot is the easy part.
When you look down the road to real products there are various
methods of software update/recovery chosen depending upon
the environment, device and features.

> Any advice/gotchas/hints as I start down this path?

There are various open source boot rom projects that you
can use to find examples of doing this.  If you don't want
to replace yamon on the board, just write some code (from
the boot rom examples) that initializes the PCMCIA, knows
how to peruse the file system of your choice, can read
the kernel into memory and jump to it.  Put this code
someplace in the flash so you can start it from yamon.

Depending upon the tools you have, this is probably
the "best" because it doesn't affect a working boot
rom on the board, just extends it use.


	-- Dan

Re: Pb1500 and PCMCIA booting?

[Greg Herlein]

> just write some code (from the boot rom examples) that
> initializes the PCMCIA, knows how to peruse the file system of
> your choice, can read the kernel into memory and jump to it.  
> Put this code someplace in the flash so you can start it from
> yamon.

Sounds good.  Looks like I should be able to create a two 
partition CF card that has the kernel on one partition and the 
root filesystem on another.  Then, do as you suggest and cook up 
some raw code that can put the Au1500 in reset and access the CF 
directly, read the kernel into memory and jump to it.  If the 
kernel is rigged to then mount the root filesystem from the other 
partition, then I have a workable system on one CF.

For the real product, the cooked code that yamon would load 
would replace yamon and get loaded as a bootloader directly.

If anyone has suggestions, references, or comments, I'd love to 
hear them.

Greg