linux-kernel - Re: [PATCH v3 3/6] [SCSI] runtime resume device before system suspend

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Date:	Thu, 24 Nov 2011 15:01:10 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Lin Ming <ming.m.lin@...el.com>,
	"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>,
	Jeff Garzik <jgarzik@...ox.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	James Bottomley <JBottomley@...allels.com>,
	"Huang, Ying" <ying.huang@...el.com>,
	"Zhang, Rui" <rui.zhang@...el.com>
Subject: Re: [PATCH v3 3/6] [SCSI] runtime resume device before system suspend

Hello,

On Thu, Nov 24, 2011 at 2:54 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> Therefore, when entering the SUSPEND or HIBERNATE stages of system
> sleep, we can skip the callback to the driver if the device is already
> in runtime suspend.  When entering the FREEZE stage, however, we should
> first issue a runtime resume.  The overhead of doing this is
> negligible, because a suspended drive would be spun up during the THAW
> stage of hibernation anyway.

My brain is half fried at the moment so maybe you're saying the same
thing, but I hope this is something simple. Like...

    /* for libata runtime suspend is equivalent to suspend */
    if (runtime suspended && target == SUSPEND) {
        yeah! skip drive pm ops;
    } else {
        end runtime pm;
        ask EH to enter target PM state;
    }

I really don't think we need to optimize this further than this.

Thanks.

-- 
tejun
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