[LAU] USB on ThinkPad T520
xiphmont at gmail.com
Sun May 13 20:40:28 UTC 2012
On Sun, May 13, 2012 at 4:06 PM, Robin Gareus <robin at gareus.org> wrote:
> Any hints on how to address this issue, then? If I understand correctly,
> new USB2-class-compliant devices are not an issue, but on modern
> machines with only EHCI, USB1-class-compliant devices may or may not
> work... right?
The primary problem with EHCI is only bandwidth allocation; it's
inefficient. I'm unaware of any timing problems. That's not to say
they don't exist, I just haven't run into them myself.
Poor bandwidth efficiency aside, I usually see ~ the same latency and
timing behavior on UHCi and EHCI with a TT.
> Would forward porting your schedulers be an option? Has anything of this
> been merged into recent kernels?
I'm unlikely to do this unless I need it myself, sorry :-(. Not
enough time, too much to do. And the kernel devs are absolutely right
that replacing a working but inefficient driver with a brand new one
that is faster but will require long-term testing is not something to
be done lightly.
> Maybe you can do play some tricks on the EHCI controller/scheduler: add
> an old USB1.1 hub in between the soundcard and the PC... but that's just
> a shot in the dark.
You'll still be going through the translator in the root hub.
More information about the Linux-audio-user