linux-kernel - Re: [RFC] ata port runtime pm

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Message-ID: <4EAA2392.40105@pobox.com>
Date:	Thu, 27 Oct 2011 23:37:54 -0400
From:	Jeff Garzik <jgarzik@...ox.com>
To:	Lin Ming <ming.m.lin@...el.com>
CC:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	Tejun Heo <tj@...nel.org>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Priyanka Gupta <ankaguptaca@...il.com>,
	Zhang Rui <rui.zhang@...el.com>,
	"Huang, Ying" <ying.huang@...el.com>
Subject: Re: [RFC] ata port runtime pm

On 10/27/2011 11:21 PM, Lin Ming wrote:
> @@ -3208,6 +3209,11 @@ int ata_scsi_queuecmd(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
>
>   	ap = ata_shost_to_port(shost);
>
> +	if (pm_runtime_suspended(&ap->tdev))
> +		pm_runtime_resume(&ap->tdev);
> +	pm_runtime_mark_last_busy(&ap->tdev);
> +	pm_request_autosuspend(&ap->tdev);
> +
>   	spin_lock_irqsave(ap->lock, irq_flags);
>


Putting this into the core command dispatch fast-path is rather 
disappointing.  That's at least one additional lock, plus some atomic 
instructions and tests.

	Jeff


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