Message-ID: <52560879.8000001@intel.com>
Date: Thu, 10 Oct 2013 09:52:57 +0800
From: Aaron Lu <aaron.lu@intel.com>
MIME-Version: 1.0
To: Phillip Susi <psusi@ubuntu.com>, Alan Stern <stern@rowland.harvard.edu>,
        Jens Axboe <axboe@kernel.dk>, "Rafael J. Wysocki" <rjw@sisk.pl>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        Tejun Heo <tj@kernel.org>
CC: linux-pm@vger.kernel.org, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org,
        Aaron Lu <aaron.lwe@gmail.com>, Shane Huang <shane.huang@amd.com>,
        Oliver Neukum <oneukum@suse.de>
Subject: Re: block layer runtime pm and udisks
References: <1364010148-8584-1-git-send-email-aaron.lu@intel.com> <5256058F.3010802@ubuntu.com>
In-Reply-To: <5256058F.3010802@ubuntu.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On 10/10/2013 09:40 AM, Phillip Susi wrote:
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> I have been trying out the new block layer runtime pm, and run into a
> problem: udisks keeps waking up the disk.  Every 10 minutes it tries
> to poll the SMART status of the drive, but it does first issue an ata
> CHECK POWER command to see if it is in standby, and skips the check to
> avoid waking the disk.  The problem with runtime pm is that *any*
> request brings the drive out of suspend, and the suspend wake path
> forces the drive to spin up by issuing a verify command on sector 0.
> 
> Is there a reason that the wakeup path forces the drive to spin up, or
> could this be removed and rely on the drive waking up automatically if
> the request requires it?
> 
> Or would it be possible to notice that the command being sent is a
> check power command, and fake the reply instead of resuming the device?
> 
> Or does udisks just need to check the runtime pm status before trying
> the check power command?

I think the udisks can be modified to check if the drive is runtime
suspended and if so, avoid poll the SMART status.

Thanks,
Aaron

> 
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