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

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Message-ID: <20120925083029.GG31374@n2100.arm.linux.org.uk>
Date:	Tue, 25 Sep 2012 09:30:29 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	"Poddar, Sourav" <sourav.poddar@...com>
Cc:	gregkh@...uxfoundation.org, khilman@...com, paul@...an.com,
	tony@...mide.com, linux-kernel@...r.kernel.org, balbi@...com,
	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 01:52:03PM +0530, Poddar, Sourav wrote:
> Hi Greg,
> 
> Ping on this?
> 
> On Tue, Sep 18, 2012 at 6:10 PM, Sourav Poddar <sourav.poddar@...com> wrote:
> > Greg's tty-next is not booting on 2420 based N800. The failure is
> > observed at serial init itself. The reason might be that n800 tries to
> > resume even though it is not suspended before.

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.
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