linux-kernel - Re: [RFC][PATCH 3/4] PCI / ACPI PM: Platform support for PCI PME wake-up (rev. 2)

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Date:	Fri, 9 Oct 2009 12:23:20 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Linux PCI <linux-pci@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Shaohua Li <shaohua.li@...el.com>,
	Bjorn Helgaas <bjorn.helgaas@...com>
Subject: Re: [RFC][PATCH 3/4] PCI / ACPI PM: Platform support for PCI PME
	wake-up (rev. 2)

On Fri, Oct 09, 2009 at 12:54:18AM +0200, Rafael J. Wysocki wrote:

> Unfortunately, the subset of PCI devices that have GPEs associated
> with them is quite limited and the other devices have to rely on
> the GPEs associated with their upstream bridges and, possibly, the
> root bridge to generate ACPI wake-up events in response to PMEs from
> them.  Moreover, ACPI devices tend to share wake-up GPEs, in which
> cases it makes sense to install an ACPI notify handler for only one
> of them and "bind" the other devices to it.  Furthermore, ACPI-based
> PCI hotplug also uses ACPI notify handlers that in general may
> conflict with the PM notify handlers, unless this issue is
> specifically taken care of.

I'm not sure this approach is correct - for instance, from a Dell 
system:

        Method (_L0D, 0, NotSerialized)
        {
            Store (SMI (0xC6, 0x00), Local0)
            If (And (Local0, 0x01))
            {
                Notify (\_SB.PCI0.AZAL, 0x02)
            }

            If (And (Local0, 0x02))
            {
                Notify (\_SB.PCI0.EHCI, 0x02)
            }

            If (And (Local0, 0x04))
            {
                Notify (\_SB.PCI0.EHC2, 0x02)
            }
        }

All these devices share a GPE, but registering only one notify handler 
would result in us missing the notification in some cases. I also 
suspect that this should wait until the GPE rework is done.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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