Re: [LAU] USB on ThinkPad T520

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To: Robin Gareus <robin@...>
Cc: A list for linux audio users <linux-audio-user@...>
Date: Sunday, May 13, 2012 - 7:28 pm

> The idea is to use the uhci_hcd (USB1) driver instead of ehci_hcd

You do not have a UHCI controller. You only have EHCI controllers.
On your machine, all USB 1.1 is handled by transaction translators in
your EHCI controller's root hub.

The UHCI driver is not a USB 1.1 driver-- it's a driver for UHCI
hardware which happens to be for USB 1.1, and which you do not have at
all. Older machines paired a UHCI and EHCI controller to handle USB
1.1 and 2.0; newer machines use EHCI for both.

The linux EHCI TT scheduler is not very good. I wrote a new one from
scratch a few years ago, but the kernel people considered it low
priority and I got sick of maintaining it against updates, as they
dropped it from testing kernels whenever any other incoming patch
conflicted. OTOH, the EHCI hardware itself is much more reliable than
the UHCI hardware, which apparently suffers from isochronous dropouts
even when the driver functions perfectly.

Monty
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Messages in current thread:
[LAU] USB on ThinkPad T520, plutek, (Sat May 12, 2:52 pm)
Re: [LAU] USB on ThinkPad T520, Clemens Ladisch, (Sat May 12, 6:31 pm)
Re: [LAU] USB on ThinkPad T520, plutek, (Sun May 13, 1:12 am)
Re: [LAU] USB on ThinkPad T520, Clemens Ladisch, (Sun May 13, 9:07 am)
Re: [LAU] USB on ThinkPad T520, Karsten Wiese, (Sat May 12, 9:18 pm)
Re: [LAU] USB on ThinkPad T520, plutek, (Sun May 13, 1:13 am)
Re: [LAU] USB on ThinkPad T520, Robin Gareus, (Sun May 13, 6:57 am)
Re: [LAU] USB on ThinkPad T520, plutek, (Sun May 13, 5:45 pm)
Re: [LAU] USB on ThinkPad T520, Robin Gareus, (Sun May 13, 6:15 pm)
Re: [LAU] USB on ThinkPad T520, Monty Montgomery, (Sun May 13, 7:28 pm)
Re: [LAU] USB on ThinkPad T520, Robin Gareus, (Sun May 13, 8:06 pm)
Re: [LAU] USB on ThinkPad T520, Monty Montgomery, (Sun May 13, 8:40 pm)
Re: [LAU] USB on ThinkPad T520, plutek, (Mon May 14, 4:31 pm)
Re: [LAU] USB on ThinkPad T520, david, (Mon May 14, 6:23 pm)
Re: [LAU] USB on ThinkPad T520, plutek, (Mon May 14, 7:20 pm)
Re: [LAU] USB on ThinkPad T520, plutek, (Mon May 14, 7:22 pm)
Re: [LAU] USB on ThinkPad T520, david, (Wed May 16, 8:25 am)
Re: [LAU] USB on ThinkPad T520, hermann, (Wed May 16, 8:33 am)
Re: [LAU] USB on ThinkPad T520, david, (Thu May 17, 5:45 pm)
Re: [LAU] USB on ThinkPad T520, Tim Westbrook, (Fri May 18, 6:57 am)
Re: [LAU] USB on ThinkPad T520, Clemens Ladisch, (Sun May 13, 8:29 pm)
Re: [LAU] USB on ThinkPad T520, plutek, (Sun May 13, 6:32 pm)
Re: [LAU] USB on ThinkPad T520, Monty Montgomery, (Sun May 13, 2:56 am)