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

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Date:	Fri, 17 Feb 2012 09:12:06 +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-ide@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [RFC PATCH 2/6] ACPI: Reference devices in ACPI Power Resource

On Thu, 2012-02-16 at 10:13 -0500, Alan Stern wrote:
> On Thu, 16 Feb 2012, Zhang Rui wrote:
> 
> > > I'm not exactly sure what you're trying to achieve and what you mean by
> > > "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
> > child device in the parent's .runtime_resume callback.
> > So I introduced these two APIs so that an runtime_resume request can be
> > 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,
> or should it be possible to suspend the ZPODD while the port remains
> running?

We want to ZPODD always to be suspended and resumed along with the ATA
port.

Below is part of the GPE handler for ZPODD device attention event.

        Scope (\_GPE)
        {
            Method (_L13, 0, NotSerialized)
            {
                ADBG ("ZPODD DA Event")
                ....

                Notify (\_SB.PCI0.SAT0.PRT2, 0x02)
                ....
            }
        }

It maybe a bit confused, but actually, \_SB.PCI0.SAT0.PRT2 is bind to
the attached device, not the ata port itself.

See below commit in linux-next tree.
75d22c(libata: Bind the Linux device tree to the ACPI device tree)

And below notify handler(PATCH 6) will resume the attached device(CDROM
in ZPODD case).

+static void ata_acpi_wake_dev(acpi_handle handle, u32 event, void *context)
+{
+       struct ata_device *ata_dev = context;
+
+       if (event == ACPI_NOTIFY_DEVICE_WAKE && ata_dev)
+               scsi_autopm_get_device(ata_dev->sdev);
+}
+

But the code to power on/power off the device is in ata_acpi_set_state,
which is called when ata port is resumed/suspended.

ata_eh_handle_port_resume/suspend
    ata_acpi_set_state
        ata_for_each_dev {
            acpi_bus_set_power(<the acpi handle of the device>, acpi_state)
        }

Could you take a look at PATCH 6?
It's more clear over there.

Thanks,
Lin Ming

> 
> Alan Stern
> 


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