Re: usb suspend backtraces.

On Mon, Jul 16, 2007 at 10:38:48AM -0400, Alan Stern wrote:

 > > -static int usb_autosuspend_delay = 2;		/* Default delay value,
 > > +static int usb_autosuspend_delay = 0;		/* Default delay value,
 > >  						 * in seconds */
 > >  module_param_named(autosuspend, usb_autosuspend_delay, int, 0644);
 > >  MODULE_PARM_DESC(autosuspend, "default autosuspend delay");
 > 
 > Ooh!  Don't do that.  Starting in 2.6.22, setting the delay to 0 means
 > "autosuspend as soon as possible".  (It was different in 2.6.21.) The
 > variable now needs to be set to -1 to prevent autosuspending.

Ah, missed that. Thanks.

 > > in usb_autopm_do_device()
 > > I'm suspecting logic is underflowing here causing this.
 > 
 > Yes, that's what it means.  I'm puzzled as to how this could occur; let 
 > me try some tests.  What types of devices give rise to these warnings?

On the machine I tried it on, there's nothing really exotic..
lsusb shows..
Bus 005 Device 054: ID 0781:5150 SanDisk Corp. SDCZ2 Cruzer Mini Flash Drive (thin)
Bus 005 Device 002: ID 050d:0234 Belkin Components F5U234 USB 2.0 4-Port Hub
Bus 005 Device 001: ID 0000:0000  
Bus 004 Device 003: ID 0aec:3050 Neodio Technologies Corp. ND3050 8-in-1 Card Reader
Bus 004 Device 001: ID 0000:0000  
Bus 003 Device 001: ID 0000:0000  
Bus 002 Device 004: ID 04a9:1097 Canon, Inc. 
Bus 002 Device 003: ID 045e:0053 Microsoft Corp. 
Bus 002 Device 001: ID 0000:0000  
Bus 001 Device 001: ID 0000:0000  

so, usb memory stick, hub, card reader, printer, mouse.

The 28 warnings in my dmesg are all preceded by..
usb 5-1.4: new high speed USB device using ehci_hcd and address 51
usb 5-1.4: configuration #1 chosen from 1 choice

I'm not sure how that 5-1.4 relates to the above map.

oh, there's one other case, where it prints the same thing for usb 4-2:

 > The differences between setting usb_autosuspend_delay to -1 and turning 
 > off CONFIG_USB_SUSPEND:
 > 
 > 	Setting the default delay to -1 allows users to enable
 > 	autosuspend on a per-device basis.  For that matter, you
 > 	might want to add a line to the hub driver, to enable
 > 	autosuspend for hubs by default.
 > 
 > 	It adds more code to the kernel (obviously).
 > 
 > 	It changes the way suspend-to-RAM behaves: individual USB
 > 	devices get suspended as opposed to suspending an entire
 > 	bus all at once.  In theory this shouldn't matter.
 > 
 > I can't think of anything else at the moment.

Ok, thanks for the info.

	Dave

-- 
http://www.codemonkey.org.uk

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