Use the NAND scrub command with caution

Nand srcub is a command used to forcibly erase NAND Flash. When using this command in U-boot, a warning is displayed: Do not use this command easily, this command will erase the bad block table marked by the factory. Once erased, it cannot be restored.

However, in general cases, even if NAND scrub is used for U-boot, the problem does not exist because everything is normal. However, if your program requires batch production, you may not be able to handle the potential problems caused by using this command.

The NAND Flash plant tests and marks the NAND Bad blocks in a relatively wide range of temperature and voltage. These Bad blocks can still work at a certain temperature or voltage, however, it may become a potential time bomb when the condition changes at another time point. Although the Flash technology is gradually improving, a 2 GB flash memory is still allowed to have up to 40 Bad blocks at the factory. Therefore, if we erase the bad block table made by the factory and use some bad blocks as good blocks, it will bring a great chance and danger to the stability of the system. At present, I am not sure which of my predecessors left me using this command to erase flash before burning chips in batches. As a result, there are often some inexplicable system problems that cannot be started in the product, it cannot be solved for a long time.