linux-kernel - Re: [RFC PATCH 2/6] ACPI: Reference devices in ACPI Power Resource

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Date:	Tue, 21 Feb 2012 22:07:35 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	"Zhang, Rui" <rui.zhang@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Jeff Garzik <jgarzik@...ox.com>,
	Tejun Heo <tj@...nel.org>, Len Brown <lenb@...nel.org>,
	"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>
Subject: Re: [RFC PATCH 2/6] ACPI: Reference devices in ACPI Power Resource

On Fri, Feb 17, 2012 at 11:07 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> On Fri, 17 Feb 2012, Zhang, Rui wrote:
>
>> > 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.
>
> Then maybe you can use pm_runtime_no_callbacks() for the ZPODD device.
> It's explained in Documentation/power/runtime_pm.txt, and I use it for
> USB interfaces.

If pm_runtime_no_callbacks() is used, runtime PM sysfs attributes
won't be created.
Then how to disable ZPODD feature in userspace?

Currently, I use "control" file of scsi device to enable/disable
ZPODD, for example
echo auto > /sys/devices/pci0000:00/0000:00:1f.2/ata0/host1/target1:0:0/1:0:0:0/power/control
echo on > /sys/devices/pci0000:00/0000:00:1f.2/ata0/host1/target1:0:0/1:0:0:0/power/control

>
> The idea is that the ZPODD will never receive any runtime PM callbacks
> from the PM core.  Instead the ATA port callback routines will be
> responsible for power management of the ZPODD device.

Does the ATA port callback also responsible to resume its child?

For example,
/sys/devices/pci0000:00/0000:00:1f.2/ata0/host1/target1:0:0/1:0:0:0/

ata0 is resumed.

Then who will be responsible to resume host1, target1:0:0 and 1:0:0:0?

Or do you mean that we don't need to resume these devices at all?
host1 and target1:0:0 are logical devices, but I think 1:0:0:0 is not.

Thanks,
Lin Ming
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