linux-kernel - Re: [PATCH] usbnet: prevent device rpm suspend in usbnet

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Date:   Mon, 07 Nov 2016 11:32:25 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     Kai-Heng Feng <kai.heng.feng@...onical.com>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH] usbnet: prevent device rpm suspend in usbnet_probe
 function

On Fri, 2016-11-04 at 09:26 -0400, Alan Stern wrote:
> On Fri, 4 Nov 2016, Kai-Heng Feng wrote:
> 
> > Sometimes cdc_mbim failed to probe if runtime pm is enabled:
> > [    9.305626] cdc_mbim: probe of 2-2:1.12 failed with error -22
> > 
> > This can be solved by increase its pm usage counter.
> 
> This should not be needed.  The USB core increments the PM usage 
> counter of a device before probing its interfaces.

Indeed. Yet we have experimental evidence.

Kai-Heng Feng, could you please enable dynamic debugging
for 
drivers/usb/core/driver.c

so that we can see what is going on with the usage counters?

	Regards
		Oliver