RTC wakeup on shutdown


When i try to configure alarm in /sys/class/rtc/rtc0/wakealarm and then putting system to halt by ‘shutdown -h now’, after the alarm expired my system not come up out of reset. I expected that system will boot up like a normal ‘phone’ would bootup on alarm expiry when in shutdown. When i wake my system still RTC is running fine but i need to know why this wakeup doesnt happen. But in deepsleep mode, system wakes up on RTC alarm expired. Please help to understand the logic.

I’m just guessing here, but I’d say that since a Jetson has no BIOS to perform a wake (which a desktop motherboard has) that there is little chance it can boot up with power actually off. Smart phones and similar devices do not normally actually power off either, they go into a sleep mode. There may be parts of a Jetson still receiving power with the power technically off (plus there is a supercap), but no BIOS means only the kernel can wake the Jetson and in turn at least part of the kernel must stay in RAM.