[Arm-netbook] eoma68 router (qca9531)
Luke Kenneth Casson Leighton
lkcl at lkcl.net
Fri May 5 20:20:13 BST 2017
On Fri, May 5, 2017 at 8:04 PM, Stefan Monnier <monnier at 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:
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.
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