Re: question about bus_suspend and bus_resume

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On Wed, 17 Jul 2013, Alan Stern wrote:

> On Wed, 17 Jul 2013, Thomas Pugliese wrote:
> 
> > Hi,
> > What is the expected behavior if a host controller does not implement 
> > bus_suspend and bus_resume?  I am seeing that with the HWA HCD, kworker 
> > and khubd peg the CPU at 100% because the kernel is constantly calling 
> > hcd_bus_suspend and hcd_bus_resume.  The calls to hcd_bus_suspend and 
> > hcd_bus_resume fail because hcd->bus_suspend and hcd->bus_resume are NULL.  
> > I have reproduced this behaviour using 3.11rc1 all the way back to 3.9.2.
> 
> I think the expected behavior is close to what you described.  :-)
> 
> Seriously, AFAIK nobody thought about this case.  To prevent this
> problem, the HCD's start routine would have to disable runtime PM for
> the root hub, by calling
> 
> 	pm_runtime_disable(&hcd->self.root_hub.dev);
> 
> Alan Stern
> 
> 

Hi Alan.  Thanks for the response.  I tried your suggestion of calling 
pm_runtime_disable in the HCD start routine but this causes the set 
configuration request to fail on the root hub.  The output looks like 
this:

usb usb6: usb_probe_device
usb usb6: configuration #1 chosen from 1 choice
usb usb6: can't set config #1, error -13

What appears to happen is that usb_set_configuration calls 
usb_autoresume_device which eventually results in a call to rpm_resume 
which fails with -EACCES.  This causes usb_set_configuration to bail out.  
Is there a better place to call pm_runtime_disable that would allow the 
root hub to successfully start?

Tom
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