linux-kernel - Re: [PATCH 5/5 v4] mfd: omap: usb: Runtime PM support

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Message-ID: <20110812213037.GA24803@google.com>
Date:	Fri, 12 Aug 2011 14:30:37 -0700
From:	Todd Poynor <toddpoynor@...gle.com>
To:	"Munegowda, Keshava" <keshava_mgowda@...com>
Cc:	linux-usb@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org, balbi@...com, gadiyar@...com,
	sameo@...ux.intel.com, parthab@...ia.ti.com, tony@...mide.com,
	khilman@...com, b-cousson@...com, paul@...an.com,
	johnstul@...ibm.com, vishwanath.bs@...com, nm@...com,
	vikram.pandita@...com
Subject: Re: [PATCH 5/5 v4] mfd: omap: usb: Runtime PM support

On Fri, Aug 12, 2011 at 12:20:21PM +0530, Munegowda, Keshava wrote:
> On Wed, Aug 10, 2011 at 10:01 PM, Todd Poynor <toddpoynor@...gle.com> wrote:
> >> @@ -913,12 +598,15 @@ static int usbhs_enable(struct device *dev)
> >>                               (pdata->ehci_data->reset_gpio_port[1], 1);
> >>       }
> >>
> >> -end_count:
> >> -     omap->count++;
> >> +     pm_runtime_put_sync(dev);
> >>       spin_unlock_irqrestore(&omap->lock, flags);
> >
> > Is pm_runtime_irq_safe() needed (else I think runtime PM callbacks may
> > re-enable IRQs... or there's the new *_suspend runtime PM calls that
> > may avoid this)?
> 
>  pm_runtime_irq_safe()  is not required; usbhs does not have a parent
> and it is the parent driver of
> ehci and ohci drivers.

But the above expects IRQs to be disabled during the
pm_runtime_put_sync, and synchronous calls can turn IRQs back on in
rpm_idle:

        if (callback) {
                spin_unlock_irq(&dev->power.lock);

                callback(dev);

I see other folks who know this better than me are discussing USB run
time PM and might_sleep contexts, so I'll note this concern and let
others chime in if they think there's a real problem here.


Todd
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