Building ARM in big-endian mode

[Charles Steaderman]

Quoting Ralf Corsepius <corsepiu at faw.uni-ulm.de>:

> Am Mon, 2003-02-24 um 21.34 schrieb Charles Steaderman:
> > I would like to rebuild RTEMS and my application for ARM in big-endian
> mode.
> 
> Meanwhile, having investigated a bit further, I found that 
> 
> 1. 
> * arm-rtems-gcc and arm-rtems-binutils both support big-endian arm.
> * arm-rtems-newlib currently is only built for little-endian.
> 
> => The current arm-rtems-gcc+newlib toolchain only supports
> little-endian arm.
> 
> Extending arm-rtems-gcc+newlib to support big-endianness would be
> trivial, but doesn't make much sense unless 2. below can be resolved.
> 
> 2. The arm port in RTEMS currently only supports little-endian arm, but
> probably can extended to big-endian arm without too much effort by
> someone actually using big-endian arm.
> 
> 
> So the crucial questions would be: 
> * Why do you want to use ARM in big-endian mode? 

The chip that we are working with is a NetSilicon NET+40. NetSilicon used to
support a development based upon uCLinux (Net+Lx). Unfortunately, the platform
was not super stable. NetSilicon then release a new OS (NET+OS) to support their
chip which is based on ThreadX and the Fusion(?) network stack. It appears to be
stable, but performance is terrible (drops 30% of flood ping packets) and it
doesn't support routing. I had hoped that a port of RTEMS to NET+40 would be
more stable than the Net+Lx port, but so far we still have frequent Data Abort
situation. We based the RTEMS ethernet driver off of the NET+OS driver. One key
difference between NET+OS and the other OSs is that NET+OS is built for big
endian. I fear that there is a DMA/Ethernet problem in the NET+40 chip that
somehow works better in big endian mode, but I can't prove this.

> * What is it that prevents you from using little endian arm?
> * Would you be willing to extend RTEMS arm port to big endianness?
> 
> Ralf
> 
> 
> 


-- 
Charlie Steaderman
charlies at poliac.com
VP Engineering
Poliac Research Corporation
Phone: 952.707.6245
Cel: 612.242.6364