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

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Date:	Fri, 12 Aug 2011 18:19:29 -0500
From:	"Menon, Nishanth" <nm@...com>
To:	Todd Poynor <toddpoynor@...gle.com>
Cc:	"Munegowda, Keshava" <keshava_mgowda@...com>,
	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, vikram.pandita@...com
Subject: Re: [PATCH 5/5 v4] mfd: omap: usb: Runtime PM support

On Fri, Aug 12, 2011 at 16:30, Todd Poynor <toddpoynor@...gle.com> wrote:
> 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.

It is rather easy with the following patch applied to pull this bug out!
https://patchwork.kernel.org/patch/1001572/

Regards,
Nishanth Menon
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