Powerd vs serial ports

[djzort]

Matthew Dillon recently posted the following bug in dragonflybsd's powerd man page that allowing powerd to put the cpu below 1500Mhz can result in serial ports losing characters (at 115200)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/17f399fd1e219df0072ba7c58df3c5a4de548809

I am uncertain if this is impacting my fleet of A10's but am experimenting if it is what causes USB huawei modems to have regular lock ups. The AMD GX-416RA SOC at 1600Mhz would certainly being crossing this threshold regularly

It is also not clear what the impact would be if the cpu is already below 1500Mhz, for example the GX-412TC which is at 1200Mhz (on APU's)

Posting this here for discussion etc.