+++ This bug was initially created as a clone of Bug #124114 +++ Description of problem: Customer is seeing messages of this sort: Aug 25 16:31:10 fclassdb kernel: hub 4-0:1.0: over-current change on port 2 while using the RHEL-4 U4 kernel. Unloading both the ehci_hcd and uhci_hcd modules caused the messages to stop printing; however, having either of the two modules (or both) installed caused these messages. The hardware is an HP ML70 i686 machine; I'll attach the dmidecode here as well.
Created attachment 139347 [details] dmidecode from affected HP ML70 system
Pete, Do you know if these messages are relatively benign, or if they are actually a problem? The customer doesn't have any USB devices installed, and is wondering whether this indicates a problem or if it's just a false positive. Thanks, Chris Lalancette
Chis asks, if these messages are benign. The answer: depends. They do not affect operation of devices which are plugged into ports and enumerated. But they are not entirely harmless, for two reasons. #1: khubd is stuck for 500ms every time this happens, so this delays the processing of connects and disconnects; #2: As part of the recovery from the overcurrent, power is re-enabled on all ports. If hub has coarsely grained power, this may affect other ports. I don't know if this is an issue on ML70. Navid asks, if there's a hardware problem. Yes, it's likely, although it may be a firmware problem. These messages happen (most likely) if (a) the southbridge's harness is improperly designed and/or implemented and shunts the power to the ground, or (b) the descriptors of the hub do not match the actual hardware and we access ports which do not exist. Neither of these should be fatal, it's the recovery which makes it bad. We should not fill up the logs with these messages. What to do? I don't know right away. We cannot ignore overcurrent indications. So, ideally we ought to devise a way to detect a broken port and somehow disable it (until... what? reboot?)
Chris, do you know of a way to get access to a system with this symptom? I need to experiment, maybe get usbmon traces.
Pete, Not off-hand, although it is a certified system so we must have some around. Let me email a few people and find out...I'll get back to you. Chris Lalancette
This request was evaluated by Red Hat Product Management for inclusion in a Red Hat Enterprise Linux maintenance release. Product Management has requested further review of this request by Red Hat Engineering, for potential inclusion in a Red Hat Enterprise Linux Update release for currently deployed products. This request is not yet committed for inclusion in an Update release.
This request was previously evaluated by Red Hat Product Management for inclusion in the current Red Hat Enterprise Linux release, but Red Hat was unable to resolve it in time. This request will be reviewed for a future Red Hat Enterprise Linux release.