The role of arm watchdog

        Watchdog is generally a hardware module. In embedded operating systems, a common application scenario is that the system runs for a long time without anyone watching. When the system freezes, the watchdog will automatically restart the system for you.

        The implementation principle of watchdog:

        The watchdog hardware has a record timeout function, and then requires the user to perform certain operations on it at a certain time interval (this time can be configured according to your needs), such as writing some fixed values ​​in it, commonly known as "feeding the dog", then I find that the timeout has expired, that is, you have not fed me after the set time, then I will think that your system is frozen and there is a problem, and I will help you reset the system. To put it simply, it is like getting a watchdog, you have to feed it regularly, if you do not feed it within the timeout, then the dog will think that you, its owner, your system, is frozen, and it will help you reset the system.

        Why turn off the watchdog when the system is initialized?

        After understanding the principle of watchdog, this problem is easy to understand. If watchdog is not disabled, then you have to write a separate program to regularly "feed the dog", which is so troublesome and boring. After all, we are only using uboot to initialize the necessary hardware resources and system resources here, and we don't need this watchdog mechanism at all. If you need to use it, it is because your Linux kernel is running, which is something your system cares about, and has nothing to do with my uboot, so you must turn off watchdog (its reset function) here.