linux-kernel - Re: PNP: do not stop/start devices in suspend/resume path

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Message-ID: <20071213092621.7cf6ee87@poseidon.drzeus.cx>
Date:	Thu, 13 Dec 2007 09:26:21 +0100
From:	Pierre Ossman <drzeus@...eus.cx>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
Cc:	Jiri Slaby <jirislaby@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>, matthew@....cx,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-pm@...ts.linux-foundation.org, linux-acpi@...r.kernel.org,
	Adam Belay <ambx1@....rr.com>,
	Matthieu Castet <castet.matthieu@...e.fr>,
	Li Shaohua <shaohua.li@...el.com>, Len Brown <lenb@...nel.org>,
	Kristen Carlson Accardi <kristen.c.accardi@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: PNP: do not stop/start devices in suspend/resume path

On Thu, 6 Dec 2007 16:25:57 -0700
Bjorn Helgaas <bjorn.helgaas@...com> wrote:

> PNP: do not stop/start devices in suspend/resume path
> 
> Do not disable PNP devices in the suspend path.  We still call
> the driver's suspend method, which should prevent further use of
> the device, and the protocol suspend method, which may put the
> device in a low-power state.
> 
> I'm told that Windows puts devices in a low-power state (Linux
> does this in the protocol suspend method), but does not use _DIS
> in the suspend path.  Other relevant references:
> 
>   - In the ACPI 3.0b spec, I can't find any mention of _DIS in
>     connection with sleep.  And Device Object Notifications,
>     Section 5.6.3, Table 5-43, says we should get a bus check
>     after awakening if hardware was removed while we slept.
> 
>   - This: http://msdn2.microsoft.com/en-us/library/ms810079.aspx
>     makes a similar point about how the OS re-enumerates devices
>     as a result of a power state change (3rd last paragraph of
>     text).
> 
>   - This: http://msdn2.microsoft.com/en-us/library/aa489874.aspx
>     suggests that Windows only stops a device to rebalance hardware
>     resources.
> 
> Signed-off-by: Bjorn Helgaas <bjorn.helgaas@...com>
> 

Tested-by: Pierre Ossman <drzeus@...eus.cx>

No noticeable issues with suspend or hibernate using this patch.

Rgds
Pierre

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