On 1/20/08, David Brownell <[EMAIL PROTECTED]> wrote: > > > > Sorry ... I thought he had posted lcpci showing a NEC controller > > > with EHCI *and* OHCI. > > > > It is a NEC controller with both. But I have 1.0 hub plugged in with > > three 1.0 devices in it. The 1.0 hub causes the OHCI controller in > > the NEC to be used. > > > > I have had even worse luck trying to get three USB audio devices > > working on 2.0. That NEC chip is a single-TT EHCI implementation. > > Actually it's a NEC chip with a zero-TT implementation. ;) > > I forget why our high speed root hubs lie about having a TT. > They probably don't need to do that, except for the ones that > don't have companion controllers. Like the silicon using the > IP from ARC, Mentor, and so on. > > > > USB plug and play sure doesn't work very well with three audio > > devices. > > I didn't catch those details. What do you mean by that? Do > they not enumerate? Do their drivers not get loaded? Is some > userspace setup missing? Or do the drivers misbehave?
I tried this setup a while ago on a single-TT 2.0 hub. It would seem that 4.2Mb of audio data wouldn't fill up a 480Mb channel. But that's when I learned about single-TT hubs, the audio would drop out because of scheduling problems. I tried some of the scheduling patches which helped but didn't fix it 100%. There's a thread about it in archives somewhere. I think you were helping, it was about nine months ago. Someone suggested that I switch to a 1.0 hub. I've been using the 1.0 for the last nine months. The only problem is that it drops all of the devices about once every 20 hours. I'll giving up on building a new kernel for the slug, there are way too many manual steps involved. http://www.nslu2-linux.org/wiki/Debian/BuildImage It's just taking too long. I'll ask on the NSLU2 ground maybe someone will point me at an automated x86 build environment. > Disconnecting isn't what I'd call a PNP issue. I think of PNP as being able to plug in three 1.0 audio devices and have it work on the first try without going through three different hubs (1.0, 2.0 single-tt, 2.0 multi-tt) to find one that works reliably. > > > > I'd like to be able to use six with the NSLU2, it has enough > > CPU power. But I can't even get three to work reliably. > > It might not have enough DMA capacity; there are other issues > that can affect system capability... With USB 2.0 It can do 22MB/sec to the disk cache and 6MB/sec to the disk. DMA seems to be ok. This is on the same controller. Disk is only very lightly used when playing music. I'm 58% idle on the CPU with three streams playing. Half of the memory is in use, the other half is cache. > > > > So if I get a 2.0 hub with multi-TT, and plug it into the NEC chip > > whose EHCI hub is only single-TT, does this have a chance of working? > > It has a chance of working, yes. Only one TT is ever involved > with a given full or low speed device, and it'll be found in > the nearest upstream hub running at full speed. While you're > connecting to the root hub, the nearest such hub is OHCI and > no TT matters. If you connect a multi-TT hub, that's what will > matter. > > > > What I need are 2.0 audio devices but they don't appear to exist. > > Some exist, but they're not common. ISTR they were geared for > sound card replacement -- and thus needed lots of channels. Normally > audio doesn't need much bandwidth, so there's no point in paying > any of the extra costs implied by high speed support. > > - Dave > -- Jon Smirl [EMAIL PROTECTED] - To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
