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Request for comments - Redboot load command writing directly to flash

This patch is not complete, hence the RFC.

I've made some changes to allow the "load" command in Redboot
to write directly to flash.  Although I've only tested it on EB40a,
it may well work on other boards.


I'm working on a where the hardware is based upon the Atmel EB40a. 
The production board is as the EB40a, except with an additional
FPGA and no possibility of expanding RAM. This leaves me
with 256kb of ram and 2mb of flash, hence loading data into
ram before flashing isn't terribly convenient.


load -f 0x10000 -b 0x1100000 -r -m ymodem

Erases 0x10000 bytes of flash starting at 0x1100000 and writes
the uploaded file directly to 0x1100000


- There is a bit of an impedance mismatch between Redboot and
the io/flash API. My first step in dealing with this was to
create a flash programming function in io/flash that writes
a single byte and does not produce debug output

- Should the argument to the -f option should be removed? Changed
to maximum length?

- I've purposly removed the flash memory range check in order
to be able to flash new versions of redboot rom using redboot 

- Is there a sufficent ymodem CRC check good enough...?

- Flashed image should be verified

- I tried to modify the serial port rate on my EB40a to >38400,
but it didn't work. There may be trouble with any
baudrate != 38400 on EB40a, but I haven't checked.

- I'm not quite sure why it works as well as it does :-)
AFAIK, Redboot does not run with interrupts enabled and if
Redboot is off flashing a byte, whos servicing the serial port?
As is, I assume that there is a fairly big HW fifo on my EB40a
board, and thats why it works as well as it does.


Attachment: directtoflashpatch.txt
Description: Text document

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