Re: hub (chip GL850A) not working

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Thu, 22 Jun 2006, Norbert Schmidt wrote:

> Hello,
> 
> USB-2.0 hubs with a GL850A chip do not work.
> (http://www.genesyslogic.com/eimages_product/GL850A%20Datasheet_165.pdf)
> 
> It seems to be a bug, is here the right place for this?

>From your description, it's more likely to be a hardware problem.  Either 
with the USB cables or maybe with the EHCI host controller on your 
computer.

> Plugging in the hub gives:
> 
> usb 1-4: new high speed USB device using ehci_hcd and address 46
> usb 1-4: device descriptor read/64, error -71
> usb 1-4: device descriptor read/64, error -71

This error means the controller was not able to communicate with the 
device.

> But with uhci_hcd the hub is working fine:
> # rmmod ehci_hcd
> ehci_hcd 0000:00:10.3: remove, state 1
> usb usb1: USB disconnect, address 1
> ehci_hcd 0000:00:10.3: USB bus 1 deregistered
> usb 3-2: new full speed USB device using uhci_hcd and address 2
> usb 3-2: configuration #1 chosen from 1 choice
> hub 3-2:1.0: USB hub found
> hub 3-2:1.0: 4 ports detected

Since UHCI runs so much slower than EHCI, it is much more resistant 
against sources of noise, bad cables, manufacturing defects, tolerances 
exceeded,... that sort of thing.

Alan Stern


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