[coreboot] About the USB issue on the Lenovo T420 port

[Iru Cai]

Hi,

I'm using the new Lenovo T420 port on gerrit[1] and found a bug about
USB(in my post on the gerrit page). And just now I found a work around on
this issue.

First I tested a USB disk on the buggy USB port before suspending the
system, it works fine. Then I unplugged the USB disk, suspended my system,
resume, and replugged the disk, the bug occurred. Then I unplugged the
disk, reload the ehci_pci module as follows:

rmmod ehci_pci
modprobe ehci-pci

The I plugged in the USB disk, it worked fine again.

I think the kernel message[2] gives some information about it, because it
gives two different port number on the USB device. But I know almost
nothing about USB, so I'm not sure what's happening.

[1] http://review.coreboot.org/#/c/11765/
[2] see the attached dmesg.log

Iru Cai
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