Re: block layer runtime pm and udisks

[Aaron Lu <aaron.lu@intel.com>]

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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