Re: [RFC 1/5] devcore introduce wakeup_event callback

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On Mon, 8 Sep 2008, David Brownell wrote:

> > For example the UHCI case. A GPE is fired, we need to clear/disable
> > the wakeup event. PCI bus can't handle it, as UHCI has special
> > registers for this, so we need call into device specific handling.  
> 
> So the bus-level PCI operation would end up with a device
> that's either (a) known to have fired PME#, or (b) known
> to be a device with legacy PM -- like UHCI -- which it's
> presuming has been wakeup-enabled.
> 
> Then in the (a) case it can clear PME# the normal way, and
> would rarely need to do anything else.
> 
> While in the (b) case the UHCI driver would need to have
> provided some device-specific -- not bus-generic -- op
> called like dev->driver->pm.is_wakeup(), to diddle those
> registers (only for Intel silicon, not UHCI from VIA or
> Genesys or anyone else).

What about case (c): The device uses legacy PM but the wakeup settings 
have already been handled by the ACPI AML code?  There's no need to 
clear any extra wakeup-related stuff, but it still is necessary to tell 
the driver about the event.

(As a matter of fact, I have no idea whether or not Intel's legacy PM 
for UHCI is implemented in AML.  It may vary from one BIOS to another.)

Alan Stern

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