Re: USB suspend problem with kernel 2.6.17

On Wed, 12 Sep 2007, Luiz Fernando N. Capitulino wrote:

>  Hi guys,
> 
>  We have an embedded system running kernel 2.6.17.14 (plus Mandriva patches)
> which has the following problem: when we suspend it to ram with an external
> USB device (which requires external power) attached, the machine doesn't
> come back from suspend. But it does work fine with bus powered devices
> attached.
> 
>  Unfortunately, it's not so easy to upgrade the kernel because the machine
> needs some additional patches to work. We'll try it eventually, but we'd
> like to get 2.6.17 fixed.
> 
>  We're still debugging it, and now we're going to try it with the minimum
> amount of patches.
> 
>  Something important to notice is that Alan's 'usb persist' patch is
> also applied.
> 
>  Is this problem familiar to someone? Any debugging tips?
> 
>  I've uploaded some information about the machine's hardware and
> the usb persist patch we have applied to:
> 
> http://users.mandriva.com.br/~lcapitulino/usb-bug-machine-info/
> 
> Thanks a lot.

You need some way to find out what's happening during the resume.  For 
example, a serial or network console might be able to help (or then 
again, it might not -- debugging resume problems is very difficult 
since by definition you're trying to get information out of a mostly 
non-functional system).

For testing purposes you can always try reverting the "usb persist" 
patch.

You should post a dmesg log showing what happens during a resume with 
only bus-powered devices attached; maybe it will contain some clues.

Alan Stern


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