[U-Boot-Users] Environment in EEPROM on MPC5200 based board

[Wolfgang Denk]

Hallo, Herr Schau!

In message <41B56C25.8070906 at MAZeT.de> you wrote:
>
> I'm using Lite5200 Board and tried to configure U-Boot to have
> environment in EEPROM. I use Hard I2C driver an everything works fine

Why don't you keep the environment in flash as it is no?

In my opinion using the environment in  EEPROM  is  just  asking  for
trouble. It has serious disadvantages:

* Loooooong boot  times,  which  are  also  not  deterministic  (just
  setting  the  board  to a new console baud rate can double the boot
  time, etc.)

* Less reliable -- in flash, you can have redundand flash sectors; so
  far I never heard  of  a  single  case  of  data  loss  in  such  a
  configuration. In EEPROM, you may experience the infamous "I2C Edge
  Conditions"  problem  (see  doc/I2C_Edge_Conditions)  - I have seen
  cases where a failing power supply caused slow voltage rise  times;
  when powering on such a board, the CPU would start to run, then the
  watchdog  would  resert it because the voltages were still too low.
  This happened 2...5 times for each power on. In  the  end  the  CPU
  would  run  fine,  but in 2 out of 3 boot cycles the environment in
  EEPROM was lost because of the Edge Conditions problem.

I _strongly_ recommend NOT to put the envrionment in EEPROM (nor  any
other critical data).

> When setting CFG_ENV_IS_IN_EEPROM U-Boot don't start (hang-up before any 
> messages are printed on screen).

Maybe you have some debugging enabled? This will try to use  printf()
to  the  console  when  the  "badrate"  variable  is  being  read  to
initialize the console --> deadlock.

> If anyone know something about this problem, any help is greatly 
> appreciated.

Just don't do it.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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