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

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Message-ID: <50FE5816.30703@compulab.co.il>
Date:	Tue, 22 Jan 2013 11:12:54 +0200
From:	Igor Grinberg <grinberg@...pulab.co.il>
To:	NeilBrown <neilb@...e.de>
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@...prootsystems.com>
Subject: Re: [PATCH] usb: musb: fix context save over suspend.

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It looks like Kevin has a new address:
Kevin Hilman <khilman@...prootsystems.com>

On 01/21/13 23:38, NeilBrown wrote:
> 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.
>> 


- -- 
Regards,
Igor.
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