linux-kernel - Re: [PATCH v5 5/6] ata: add ata port system PM callbacks

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Date:	Tue, 13 Dec 2011 14:07:44 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Lin Ming <ming.m.lin@...el.com>
cc:	Jeff Garzik <jgarzik@...ox.com>,
	James Bottomley <JBottomley@...allels.com>,
	Tejun Heo <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Huang, Ying" <ying.huang@...el.com>,
	"Zhang, Rui" <rui.zhang@...el.com>
Subject: Re: [PATCH v5 5/6] ata: add ata port system PM callbacks

On Wed, 14 Dec 2011, Lin Ming wrote:

> > This suggests that the PM core is not the right place to solve the 
> > problem.  One possible solution is for the subsystem or device driver 
> > to call pm_runtime_get_sync(dev->parent) at the start of the 
> > system-resume procedure and pm_runtime_put_sync(dev->parent) at the 
> > end.
> 
> How about below?
> (Not tested yet)
> 
> diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
> index a633076..5cf9a19 100644
> --- a/drivers/scsi/scsi_pm.c
> +++ b/drivers/scsi/scsi_pm.c
> @@ -71,9 +71,17 @@ static int scsi_bus_suspend_common(struct device *dev, pm_message_t msg)
>  static int scsi_bus_resume_common(struct device *dev)
>  {
>  	int err = 0;
> +	bool put = false;
>  
> -	if (scsi_is_sdev_device(dev))
> +	if (scsi_is_sdev_device(dev)) {
> +		if (dev->parent && pm_runtime_suspended(dev->parent)) {
> +			pm_runtime_get_sync(dev->parent);
> +			put = true;
> +		}

You don't need to test anything.  Always call pm_runtime_get_sync().

>  		err = scsi_dev_type_resume(dev);
> +		if (put)
> +			pm_runtime_put_sync(dev->parent);

Same here.

> +	}
>  
>  	if (err == 0) {
>  		pm_runtime_disable(dev);

Alan Stern

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