On Fri, May 5, 2017 at 8:04 PM, Stefan Monnier monnier@iro.umontreal.ca wrote:
so i would assume, because it's not an actual 10/100 ethernet, that it would run at (saturate) the full 480mb/sec of USB2. so not quite GbE speeds but pretty damn close. yay!
Based on what USB2 gives us with "mass-storage" devices, 30MB/s is basically the upper bound. And FWIW, when I connect my desktop to my A20-based router via USB2 on one side and USB-OTG on the other (using the "gether" gadget), I'm getting about 10MB/s, so "faster than fast-ethernet" maybe, but be surprised if you get "close" to GbE speeds.
g_ether over the A20's musb (Mentor USB) interface is... very broken. musb is a ridiculously-low-cost OTG controller that has to be partially-implemented in softtware. the current state of the linux driver for musb is completely fucked-up. for example: if you plug a USB3 hub into it, then plug in a USB 1.1 keyboard, it goes "aargh fuck i have no fucking idea what to do, aaiyaaa splurgh". likewise the usb speed-allication code is all screwed up: you can just about get away with plugging in one device but a hub and then multiple devices: forget it.
so what you are probably running into is the musb driver going "ha! you plugged in a *what*?? pffh i have no idea what speed that is so let's just assume it's USB 1.0 mkaay?"
a proper USB2 host controller should have none of these difficulties.
l.