Basically I want the following:
(1) board boots with watchdog enabled (2) u-boot services watchdog (3a) booting embedded linux with booti (watchdog enabled) or (3b) booting generic OS with bootefi (watchdog disabled)
The missing case is booting an embedded linux with bootefi, which would be nice to have. But I don't really see it as a use-case for our board.
For SUNXI boards disabling CONFIG_WATCHDOG_AUTOSTART solved the problem with the very short maximum expiration time of the watchdog.
I can't follow you here. What "very short maximum expiration time"? With CONFIG_WATCHDOG_AUTOSTART disabled, the watchdog won't be kicked by u-boot, right? wdt->running will never be set to true and wdt_cyclic() will be a noop.
The sunxi boards failed to boot with CONFIG_WATCHDOG_AUTOSTART because 16s is too short for Linux to install a watchdog driver. With CONFIG_WATCHDOG_AUTOSTART=n the watchdog is not running and the boards boot.
But how does that help in my case?
-michael