linux-kernel - Re: [PATCH] usb: musb: fix context save over suspend.

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Message-ID: <20130122083832.7a3026c9@notabene.brown>
Date:	Tue, 22 Jan 2013 08:38:32 +1100
From:	NeilBrown <neilb@...e.de>
To:	Igor Grinberg <grinberg@...pulab.co.il>
Cc:	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, Kevin Hilman <khilman@...com>
Subject: Re: [PATCH] usb: musb: fix context save over suspend.

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On Mon, 21 Jan 2013 13:38:59 +0200 Igor Grinberg <grinberg@...pulab.co.il>
wrote:

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> Hi Neil,
> 
> On 01/21/13 11:28, NeilBrown wrote:
> > 
> > 
> > The standard suspend sequence involves runtime_resuming
> > devices before suspending the system.
> > So just saving context in runtime_suspend and restoring it
> > in runtime resume isn't enough.  We  must also save in "suspend"
> > and restore in "resume".
> > 
> > Without this patch, and OMAP3 system with off_mode enabled will find
> > the musb port non-functional after suspend/resume.  With the patch it
> > works perfectly.
> 
> Hmmm... Some time ago, this has been removed in
> 5d193ce8 (usb: musb: PM: fix context save/restore in suspend/resume path)
> 
> Am I missing something? Or things changed and now this patch is correct?

Hi Igor,
 thanks for alerting me to that patch .... does anyone else get the feeling
 that power management to too complex to be understood by a mere human?

 That commit (5d193ce8) suggests that the musb-hdrc device is an
 'omap_device', or maybe has a PM domain set to something else.
 However it isn't/doesn't.  dev->pm_domain is NULL.  So no PM domain layer
 will ever call the musb_core musb_runtime_suspend/resume.

 The parent device - musb-omap2430 - is an omap device, does have pm_domain
 set, and does have its omap2430_runtime_suspend/resume called for system
 suspend and so the context for that device is saved and restored.
 However that doesn't help the context for musb-hdrc.

 Whether musb ever was an omap_device is beyond my archaeological skills to
 determine.

 Kevin:  Was musb-hdrc ever a device with a pm_domain? or was it only ever
     the various possible parents that had domains?
     Are you able to defend your earlier patch in today's kernel?  It
     certainly causes my device not to work properly.

Thanks,
NeilBrown



> 
> > 
> > Signed-off-by: NeilBrown <neilb@...e.de>
> > 
> > diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
> > index fd34867..b6ccc02 100644
> > --- a/drivers/usb/musb/musb_core.c
> > +++ b/drivers/usb/musb/musb_core.c
> > @@ -2225,6 +2225,7 @@ static int musb_suspend(struct device *dev)
> >  	}
> >  
> >  	spin_unlock_irqrestore(&musb->lock, flags);
> > +	musb_save_context(musb);
> >  	return 0;
> >  }
> >  
> > @@ -2234,6 +2235,8 @@ static int musb_resume_noirq(struct device *dev)
> >  	 * unless for some reason the whole soc powered down or the USB
> >  	 * module got reset through the PSC (vs just being disabled).
> >  	 */
> > +	struct musb	*musb = dev_to_musb(dev);
> > +	musb_restore_context(musb);
> >  	return 0;
> >  }
> >  
> 
> - -- 
> Regards,
> Igor.
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