linux-kernel - RE: [PATCH 4/5] usb: call pm_runtime_put_sync in pm_runtime_get

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Message-ID: <BEC9F67575FA1E429CA7CF5AE9BE3634407F48@SHSMSX102.ccr.corp.intel.com>
Date:	Thu, 28 Feb 2013 09:00:05 +0000
From:	"Li, Fei" <fei.li@...el.com>
To:	"Lan, Tianyu" <tianyu.lan@...el.com>,
	"stern@...land.harvard.edu" <stern@...land.harvard.edu>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"sarah.a.sharp@...ux.intel.com" <sarah.a.sharp@...ux.intel.com>,
	"rjw@...k.pl" <rjw@...k.pl>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Liu, Chuansheng" <chuansheng.liu@...el.com>
Subject: RE: [PATCH 4/5] usb: call pm_runtime_put_sync in
 pm_runtime_get_sync failed case

> -----Original Message-----
> From: Lan, Tianyu
> Sent: Thursday, February 28, 2013 4:37 PM
> To: Li, Fei; stern@...land.harvard.edu
> Cc: gregkh@...uxfoundation.org; sarah.a.sharp@...ux.intel.com; rjw@...k.pl;
> linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org; Liu, Chuansheng
> Subject: Re: [PATCH 4/5] usb: call pm_runtime_put_sync in
> pm_runtime_get_sync failed case
> 
> On 2013年02月28日 15:57, Li Fei wrote:
> >
> > Even in failed case of pm_runtime_get_sync, the usage_count
> > is incremented. In order to keep the usage_count with correct
> > value and runtime power management to behave correctly, call
> > pm_runtime_put(_sync) in such case.
> 
> Hi Fei:
> 	It's not necessary. Because the did_runtime_put == true means the
> port's usage count has already been decreased during
> usb_port_suspend().So to keep usage count balance, we should increase
> the usage count in the usb_port_resume() whatever.

Thanks for your reminder.
Sorry, I forget to keep did_runtime_put as false in pm_runtime_get_sync
failed case. I'll submit patch V2 to update it.

> >
> > Signed-off-by Liu Chuansheng <chuansheng.liu@...el.com>
> > Signed-off-by: Li Fei <fei.li@...el.com>
> > ---
> >  drivers/usb/core/hub.c |    1 +
> >  1 files changed, 1 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> > index 5480352..b68493b 100644
> > --- a/drivers/usb/core/hub.c
> > +++ b/drivers/usb/core/hub.c
> > @@ -3152,6 +3152,7 @@ int usb_port_resume(struct usb_device *udev,
> pm_message_t msg)
> >  		if (status < 0) {
> >  			dev_dbg(&udev->dev, "can't resume usb port, status %d\n",
> >  					status);
> > +			pm_runtime_put_sync(&port_dev->dev);
> >  			return status;
> >  		}
> >  	}
> >
> Hi Alan:
> 	Further thinking, the device should be disconnected since the port
> can't be resumed and the device will not work normally. Something like
> following. Does this make sense?
> ---
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index d5d3de4..cf36b11 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -3170,6 +3170,7 @@ int usb_port_resume(struct usb_device *udev,
> pm_message_t msg)
>                 if (status < 0) {
>                         dev_dbg(&udev->dev, "can't resume usb port,
> status %d\n",
>                                         status);
> +                       hub_port_logical_disconnect(hub, port1);

IMHO, this can't keep the usage_count balance.

Best Regards,
Li Fei 

>                         return status;
>                 }
>         }
> 
> 
> --
> Best regards
> Tianyu Lan