In message 44C0B8EC.8090405@dave-tech.it you wrote:
Use MTD tools under Linux to unlock the flash?
Indeed this is a possible solution but I'm looking for a general one implemented in u-boot. In fact it must work with any operating system and I must assume o.s. might not provide MTD or similar tools.
It is easy to postulate requirements. But seriously, if you are careless enough to use flash chips which can change modes or even lose data by just writing random data to sequential addresses then you must also accept the consequences. Either provide adequate recovery mechanisms in Linux or your OS of choice or in U-Boot.
I have to admit that I fail to understand what exactly your problem is: if you want to use the hardware protection features in U-Boot (including the unlocking of locked sectors) then just enable this feature in U-Boot.
Best regards,
Wolfgang Denk