25 May 2016, 17:32
@marco-rigoni NO! sysupgrade is not what you want.
Try the uimage u = micro, iirc, and should provide you bare minimum booting times off the bat (though probably without all the stuff you need listed above).
I think, though, uart is a deferred, with wifi + webserver as an immediate. That would mean that, if you set up your webserver correctly, you can get to minimum boot while you are awaiting the dhcp software and uart to boot. If you make a wifi connection as an initial setup (read: the user is expected to wait for a while on the first initial setup of internet access, with immediate boots thereafter), then your wifi and server can get online fairly quickly I would think. Unless of course, I'm misunderstanding your application.
The reason this approach would work is that minimum response time for a webserver is the key. People/users expect the loading of data to take a while. And, the 'retrieving data log' portion can be a pinwheel to buy you time to load the first time, right? So there is actually a lot you can do to get a product that have nothing to do with overall boot times. . .