@blue_led
the userland autospeed has one problem: it needs to either depend on sysklogd being installed or use kmsg directly. You need to support both cases, or rdepend on ksyslogd pkg.
You are aware you can find about lowspeed vs high/fullspeed devices by reading out the status registers of PHY, and IIRC they are even printed in syslog. on one the D+ is low while on other the D- is low (see USB 101 about lowspeed vs full/highspeed signalling via pullup R) [maybe the prev isn't all correct as I haven't re-read the specs myself just now, it's a while since I last looked into them]
Great to see your progress, while I clearly suck delivering that stuff :-D
Keep in mind it may take quite some time after disabling boost mode until VBUS drops to a sane level so you can switch speed. Maybe testing VBUS voltage may give a clue, or just insert a short (some 5..15s) charging phase so bq24150 will try to pull power and thus discharges VBUS rail. Otherwise musb_core might not allow proper changing of speed.

cheers and keep hacking
jOERG