linux-kernel - Re: [RFC/RFT] OHCI: Fix for regression in 2.6.37-rc1 since commit 3df7169e7

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Date:	Fri, 10 Dec 2010 18:17:58 -0600
From:	Larry Finger <Larry.Finger@...inger.net>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	pali.rohar@...il.com, Greg Kroah-Hartman <gregkh@...e.de>,
	USB list <linux-usb@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC/RFT] OHCI: Fix for regression in 2.6.37-rc1 since commit
 3df7169e7

Alan,

The box with the problem has been repaired, and I am trying to debug it.

What I have learned so far:

The "unable to enumerate" message is triggered because PORT_OWNER is not set in
the status register.

So far, I have found that this bit is set in only 4 places:

1. set_owner()
2. store_companion()
3. ehci_hub_control()
4. ehci_relinquish_port()
5. check_reset_complete()

Of these, only #5 is called before the first enumeration message is logged, but
it is only called with arguments that never set the PORT_OWNED bit in the status.

At this point I'm at a loss. Could you please give me ideas on where I might look.

The logged data leading up to the first message are:

[    3.002762] hub 4-0:1.0: USB hub found
[    3.002780] hub 4-0:1.0: 5 ports detected
[    3.088286] ehci_hcd 0000:00:02.1: usb: Entered check_reset_complete with
port_status 0x1005
[    3.088433] ehci_hcd 0000:00:02.1: port 4 high speed
[    3.144061] usb 1-4: new high speed USB device using ehci_hcd and address 2
[    3.200286] ehci_hcd 0000:00:02.1: usb: Entered check_reset_complete with
port_status 0x1005
[    3.200437] ehci_hcd 0000:00:02.1: port 4 high speed
[    3.352298] ehci_hcd 0000:00:02.1: usb: Entered check_reset_complete with
port_status 0x1005
[    3.352304] ehci_hcd 0000:00:02.1: port 5 high speed
[    3.408071] usb 1-5: new high speed USB device using ehci_hcd and address 3
[    3.454449] PM: Starting manual resume from disk
[    3.464305] ehci_hcd 0000:00:02.1: usb: Entered check_reset_complete with
port_status 0x1005
[    3.464449] ehci_hcd 0000:00:02.1: port 5 high speed
[    3.600052] ehci_hcd 0000:00:04.1: usb: Entered check_reset_complete with
port_status 0x1001
[    3.600202] ehci_hcd 0000:00:04.1: port 5 full speed --> companion
[    3.600307] ehci_hcd 0000:00:04.1: Wrote 0x3001 to status reg
[    3.656089] hub 2-0:1.0: unable to enumerate USB device on port 5
[    3.656203] ehci_hcd 0000:00:04.1: In ehci_relinquish_port
[    3.656295] ehci_hcd 0000:00:04.1: In set_owner

Thanks,

Larry
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