Hi, alan,

-----Original Message-----
From: Alan Stern [mailto:stern@rowland.harvard.edu]
Sent: Thursday, February 16, 2012 11:14 PM
To: Zhang, Rui
Cc: Rafael J. Wysocki; Lin, Ming M; Jeff Garzik; Tejun Heo; Len Brown;
linux-kernel@vger.kernel.org; linux-ide@vger.kernel.org; linux-
scsi@vger.kernel.org; linux-pm@vger.kernel.org
Subject: Re: [RFC PATCH 2/6] ACPI: Reference devices in ACPI Power
Resource
Importance: High

On Thu, 16 Feb 2012, Zhang Rui wrote:

quoted

quoted

I'm not exactly sure what you're trying to achieve and what you

mean by

quoted

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"resume a device directly"?  Do you want to run the device's resume
callback at the time when another device is being resumed?

I mean, wakeup event is sent to ATA port, but our goal is to resume
ZPODD after receiving this wakeup event.
Ideally, it is ACPI that resumes ATA port. And then, the ATA port
runtime resumes ZPODD. But this does not look good to runtime resume

a

quoted

child device in the parent's .runtime_resume callback.
So I introduced these two APIs so that an runtime_resume request can

be

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sent to ZPODD directly and the runtime PM core can resume all the
parents of ZPODD automatically.

It's not clear what you're trying to achieve.

Do you basically want
the ZPODD always to be suspended and resumed along with the ATA port,

No. ZPODD suspends itself, which put ZPODD to a SCSI low power state (NOT power off/D3_COLD).
And then it is the "Runtime PM core" that suspends ATA port after ZPODD being suspended.
And the .runtime_suspend callback for ATA port actually turns off the ZPODD power.

During resume, ATA port is resumed first because of the ACPI wakeup event. 
But in fact, this wakeup event should be read as "ZPODD remote wakeup signal", thus runtime resume request is sent to ZPODD, done by Patch 3/6.

or should it be possible to suspend the ZPODD while the port remains
running?

Sure, but the power is still on at this time.

Thanks,
rui