linux-kernel - Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

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Date:	Tue, 25 Sep 2012 10:12:28 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Felipe Balbi <balbi@...com>
Cc:	"Poddar, Sourav" <sourav.poddar@...com>,
	gregkh@...uxfoundation.org, khilman@...com, paul@...an.com,
	tony@...mide.com, linux-kernel@...r.kernel.org,
	santosh.shilimkar@...com, linux-serial@...r.kernel.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	alan@...ux.intel.com
Subject: Re: [RFT/PATCH] serial: omap: prevent resume if device is not
	suspended.

On Tue, Sep 25, 2012 at 11:31:20AM +0300, Felipe Balbi wrote:
> On Tue, Sep 25, 2012 at 09:30:29AM +0100, Russell King - ARM Linux wrote:
> > How is this happening?  I think that needs proper investigation - or if
> > it's had more investigation, then the results needs to be included in
> > the commit description so that everyone can understand the issue here.
> > 
> > We should not be resuming a device which hasn't been suspended.  Maybe
> > the runtime PM enable sequence is wrong, and that's what should be fixed
> > instead?  
> > 
> > This sequence in the probe() function:
> > 
> >         pm_runtime_irq_safe(&pdev->dev);
> >         pm_runtime_enable(&pdev->dev);
> >         pm_runtime_get_sync(&pdev->dev);
> > 
> > would enable runtime PM while the s/w state indicates that it's disabled,
> > and then that pm_runtime_get_sync() will want to resume the device.  See
> > the section "5. Runtime PM Initialization, Device Probing and Removal"
> > in Documentation/power/runtime_pm.txt, specifically the second paragraph
> > of that section.
> 
> that was tested. It worked in pandaboard but didn't work on beagleboard
> XM. Sourav tried to start a discussion about that, but it simply died...
> 
> In any case, pm_runtime_get_sync() in probe will always call
> runtime_resume callback, right ?

Well, if the runtime PM state says it's suspended, and then you enable
runtime PM, the first call to pm_runtime_get_sync() will trigger a resume
attempt.  The patch description is complaining about resume events without
there being a preceding suspend event.

This could well be why.
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