[ECOS] ROMRAM Application on xScale (PXA255)

["Joe Porthouse" <jporthouse at toptech dot com>]

In a nutshell:
	I am attempting to locate or find the information needed to write
the code needed to finish the implement of the ROMRAM startup type on the
xScale platform.

Background:	
	I have an application on a PXA255 that requires the ability to
remotely upload new application code.  Because of how this system is used,
uploading new code must be done through the application and not redboot.
	In the past under Metroworks I did this by having a small "boot"
application copy the real "application" from flash to RAM for execution.  If
a firmware update was needed the application would capture the new
application image, and overwrite the old application image in flash.  On a
reboot the new application would be running.  Most of the other hardware
initialization occurred in the application.  Since the small boot
application did not contain any library routines for the application it to
could be updated by the application.

Were I am now:
	I currently have redboot copying my ecos application from flash to
RAM for execution, but do not know how my application can update the flash
application image that redboot will load.
	A lot of hardware initialization currently occurs in redboot.  Since
hardware initialization may also need to be updated, I also need the ability
to update redboot through the application.  Since redboot normally runs from
flash, I would not be able to update it while redboot services are still
being called by interrupts and/or the application.
	I would really like to do without redboot and have all hardware
initialization occur in my application.  I have been able to build my
application for ROM startup type and execute directly from flash without
redboot, but since it is running from flash, this prevents the application
from updating itself.

Where I would like to go:
	I would like to have the ability to build my application as a ROMRAM
startup type not using redboot.  This would enable my application to run
from RAM, but have the ability to update the flash image.  This would also
keep all initializations and application in one image that is easy to
update.
	The only problem I have is that I can not find any examples of a
ROMRAM startup type on the PXA255 or any xScale processor.  ROMRAM also does
not show up as a startup type option in the configtool.  (I figured it has
not been implemented on this platform yet).  I do see some #ifdefs in
vectors.S and other code for ROMRAM, but it does not look complete.  I can
see where the .DATA segment gets copied into RAM, but I do not see any code
for copying the .TEXT segments from ROM to RAM.

	Any ideas out there for supporting the ROMRAM startup type on the
xScale (PXA255)?
Thanks,
Joe Porthouse
Toptech Systems, Inc.
280 Hunt Park Cove
Longwood, FL 32750




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