[U-Boot-Users] Multiple flash Support

[Ulf Samuelsson <ulfs@dof.se>]

> In message <000e01c6c752$e8502510$654765d5@atmel.com> you wrote:
>>
>> Maybe this is too late, 
>> but it may make sense to add an 8 kB serial EEPROM to a board
>> (which is probably a development board anyway)
>> and store the environment in this chip.
> 
> No! Please DON'T do this.
> 
> I recommend against using EEPROM (at least on I2C) for any  important
> data.  See  doc/I2C_Edge_Conditions  for  just  one problem which can
> cause data loss on such devices. Don't  say  this  is  a  theoretical
> issue. I know of systems that suffered from this.
> 

There are plenty of serial EEPROMs (and Serial Flash) and some are on I2C and other are on SPI.
A very large percentage of my customers only have an SPI flash on the board and nothing else.

If this indeed is a development board, cost is probalby not a big issue.
A 4 Mbit serial flash in an SO-8 is anyway dirt cheap and runs at 66 Mbps or 8,25 MByte/s

The U-boot dataflash driver does not support so small dataflashes, but you can 
add a 16 Mbit CASON-8 package in the same foot print and set the
CONFIG_ENV_IN_DATAFLASH (IIRC) and a few other things, (see include/configs/at91rm9200dk.h)
and off you go.
 
A small patch to the dataflash driver should allow the use of the smaller size.
The main issue will be the fact that the sectors are 512+16 bytes instead of 1024+32 bytes

> Also, EEPROM is slow to read, and  adds  for  LONG  and  random  boot delays.
> Best regards,
> 
> Wolfgang Denk
> 

Best Regards
Ulf Samuelsson