[openfirmware] On Raspberry Pi

Mitch Bradley wmb at laptop.org
Wed Jun 26 03:58:48 CEST 2013



On 6/25/2013 2:22 PM, James Cameron wrote:
> On Fri, Sep 14, 2012 at 08:19:28PM +0000, Mark Morgan Lloyd wrote:
>> Is it possible to put OpenFirmware on an SD card and use it to boot
>> off e.g. a USB-attached mass storage device or using TFTP over a
>> LAN?
> 
> I've now a Raspberry Pi (B).
> 
> The armforth.static in the openfirmware repository as of now (r3683)
> seems to run:
> 
> % cpu/arm/Linux/armforth.static cpu/arm/build/builder.dic
> ok bye
> % 
> 
> and rebuilding it seems to work fine:
> 
> % (cd cpu/arm/Linux; make)
> ...
> % cpu/arm/Linux/forth cpu/arm/build/builder.dic
> ok bye
> % 
> 
> and rebuilding the builder seems to work fine:
> 
> % (cd cpu/arm/build; make)
> ...
> % cpu/arm/Linux/forth cpu/arm/build/basefw.dic
> ok no-page to-file test words
> ok bye
> % 
> 
> So user-mode is probably okay, and a useful tool.
> 
> It is said [1] that the SoC loads various files and runs them on the
> (closed) GPU.  It then loads kernel.img and runs it on the ARM.
> 
> % file /boot/kernel.img
> kernel.img: Linux kernel ARM boot executable zImage (little-endian)
> % 
> 
> I'm not planning a port, but I thought I'd mention what I've found so
> far, in case anybody is interested.  The porting would be drivers for
> serial, SD, ethernet, and USB, possibly using the kernel sources as
> reference, given that there's very little data available.

http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf

describes the peripherals.  


The mini UART looks pretty much like the 16550 (PC COM port) UART that
everybody seems to use as a programming model these days, so no drama there.

The EMMC controller looks like the common SDHCI programming model.  Same
old same old.

The USB controller uses Synopsis IP; it seems like you can get the manual
if you register.

The Ethernet is on USB - it's inside an SMSC LAN9512 integrated USB hub/ethernet
chip.  I don't know its details, but in the past, adding OFW support for new USB
ethernet interfaces has not proven to be difficult.




> 
> References:
> 
> 1.  http://www.raspberrypi.org/phpBB3/viewtopic.php?f=29&t=10727
> 



More information about the openfirmware mailing list