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

[Pierre Ossman <drzeus@drzeus.cx>]

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

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

No noticeable issues with suspend or hibernate using this patch.

Rgds
Pierre

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