linux-kernel - Re: [PATCH] usb: musb: fix pm

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Date:	Mon, 19 Dec 2011 21:39:26 +0200
From:	Felipe Contreras <felipe.contreras@...il.com>
To:	balbi@...com
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Jarkko Nikula <jarkko.nikula@...mer.com>,
	stable@...r.kernel.org, Hema Kalliguddi <hemahk@...com>
Subject: Re: [PATCH] usb: musb: fix pm_runtime mismatch

On Fri, Dec 16, 2011 at 3:38 AM, Felipe Balbi <balbi@...com> wrote:
> On Fri, Dec 16, 2011 at 03:13:13AM +0200, Felipe Contreras wrote:
>> On Fri, Dec 16, 2011 at 1:50 AM, Felipe Balbi <balbi@...com> wrote:
>> > On Fri, Dec 16, 2011 at 01:31:02AM +0200, Felipe Contreras wrote:
>> >> On Fri, Dec 16, 2011 at 1:01 AM, Felipe Balbi <balbi@...com> wrote:
>> >> > On Fri, Dec 16, 2011 at 12:42:14AM +0200, Felipe Contreras wrote:
>> >> >> --- a/drivers/usb/musb/musb_core.c
>> >> >> +++ b/drivers/usb/musb/musb_core.c
>> >> >> @@ -2012,8 +2012,6 @@ musb_init_controller(struct device *dev, int nIrq, void __iomem *ctrl)
>> >> >>       if (status < 0)
>> >> >>               goto fail3;
>> >> >>
>> >> >> -     pm_runtime_put(musb->controller);
>> >> >
>> >> > To me the real fix would be add the missing pm_runtime_get_sync(). On
>> >> > probe() we're actually accessing MUSB's address space which needs it's
>> >> > clocks turned on. I guess it's only working now by chance, probably
>> >> > because glue layer calls pm_runtime_get_sync() to access it's own
>> >> > address space and that uses the same clocks.
>> >>
>> >> Are you sure it's "musb-hdrc", and not "musb-omap2430" the one
>> >> accessing the relevant address-space? From the runtime_pm
>> >> documentation it looks like only the probe function should deal with
>> >> this.
>> >>
>> >> If "musb-hdrc" was truly accessing these registers, then I would get
>> >> the same failure because the clocks are turned off, but I don't...
>> >
>> > see musb_core_init(); You don't see any problems when accessing those
>> > addresses because musb_platform_init() will fall into
>> > omap2430_musb_init() which calls pm_runtime_get_sync(), and the same
>> > clock actually enables both address spaces (musb-omap2430 and
>> > musb-hdrc).
>>
>> That's true, but how would I go test this theory? Call
>> pm_runtime_put_sync() at the end of omap2430_musb_init()?
>
> sounds like a plan... Not sure if it will work always though. If I
> remember correctly, pm_runtime_put_sync() will only be synchronous to
> the current device, but will go up the parent tree asynchronously. Which
> means that dev->parent will be see a scheduled runtime_put

I tested this. Nothing bad happens (until isp1704_charger actually
tries to do something, of course; the counters are messed up).

Cheers.

-- 
Felipe Contreras
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