Re: Linux 3.8-rc1 - another regression on USB :-(

From: Woody Suwalski
Date: Wed Jan 02 2013 - 08:40:52 EST

Greg Kroah-Hartman wrote:
On Sun, Dec 23, 2012 at 02:35:49PM -0800, Linus Torvalds wrote:
Any chance you can bisect this? It's not going to be hugely pleasant
(with 11k+ commits in between 3.7 and 3.8-rc1 you'll have to compile
and test at least 14 kernels), but it would help enormously. Of
course, maybe some USB person can guess what would cause the device to
go offline..

Added Greg and the linux-usb mailing list to the participants list:
the images are in the original email on lkml, but there isn't anything
particularly interesting there, it really just seems to be an
unexpected and spurious USB disconnect, resulting in "USB disconnect,
device number 2" followed by "Rejecting I/O to offline device".
I don't see any images on lkml, sorry.

The kernel log for when the disconnect happened would be great to get.

The kernel can't cause a device to disconnect, that's an electrical
thing usually, is this perchance a flaky device/connection? Or has it
always worked on older kernels?

What host controller is being used here (xhci, ehci, etc.?)


greg k-h
Greg, Linus,
It sounds insane, but after banging on the issue I have found out that USB problem is caused (also in vanilla kernel) with a config change:
USB-all built as modules - bad USB
USB core built in, UHCI/EHCI modules - semi functional - but 1Mb/s transfer
USB core and UHCI EHCI built-in - bingo - no issues.

Could anybody duplicate that, or is it somehow my setup???

Thanks, Woody

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