Dear Reinhard Meyer, In message <[email protected]> you wrote: > > > We're not concerned about u-boot's environment not being reliable, we just > > want the ability to completely erase the nand without worrying about losing > > essential data (like a MAC address). I suppose we could work around that > > area of the flash if/when > erasing the nand is necessary, but then we would have to keep track of each > environment variable that could be stored there. > > That is exactly my concern as well. > > > >> I have seen _way_ more cases where data in EEPROM got lost than data > >> loss from the environment. > > > > That's discouraging, do you have any advice for where to store the MAC > > outside of nand, and not in an EEPROM? > > I cannot second that, we have always stored environment and vital product > data in EEPROM (AT24C64). But VPD (includes MAC adresses) is never writen > by u-boot; only read and made into respective setenv() variables. Check > boards/emk/common/vpd.c for an idea.
Most people think they are safe when they only read the EEPROM. They are under a misapprehension. If you reset the processor at the right time within a I2C read command, and if you (or your I2C controller) don't take special care, the next read access might cause a write operation on that device. See doc/I2C_Edge_Conditions for details. Note that this is NOT a theoretical case. Many people have seen this. I had this myself with a customer who was switching to another, cheaper power supply. Upon power on, the voltage ramp up was relatively slow, which caused the system watchdog to reset the system 2 or 3 times because of too low voltages - and with 3 out of 5 power-ons the EEPROM content got corrupted. If you need reliable read-only storage, use NOR. Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: [email protected] grep me no patterns and I'll tell you no lines. _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
