Hi.

I have a problem in power management which am currently investigating. In a
nutshell, a child device tries bringing its stack back to D0 in order to
enable/disable wakes when system is transitioning to Sx. This is triggered
when receiving the Sx IRP which is sent down the stack after setting a
completion routine to bring the stack back to D0, set wake registers and then
transitioning it back to D3. While this works fine under 2k and XP, I get
failures under Vista (only if DTM Client is installed) and Server2k8 where
parent WDF driver fails to connect interrupts on transition to D0 (possibly
because a Sx IRP has been issued before?).

I'll probably log in more details on this later on. But while investigating
this problem I came across few strange WDF logs. As mentioned, I can see in
some cases the parent is not able to connect interrupts, thus failing
transition to D0. However when the child's completion routine is called the
IoStatus block shows a successful status which isn't what I'd expected.

Also I came across the following which is a bit more strange as you don't
expect a device to succeed powering up when it's parent has failed this
request:

Dumping WDFDEVICE 0x7b47e940
=================================

WDM PDEVICE_OBJECTs: self 848d3030

Pnp state: 119 ( WdfDevStatePnpStarted )
Power state: 32b ( WdfDevStatePowerStartSelfManagedIo )
Power Pol state: 502 ( WdfDevStatePwrPolStartingSucceeded )

Parent WDFDEVICE 7b794620
Parent states:
Pnp state: 119 ( WdfDevStatePnpStarted )
Power state: 33e ( WdfDevStatePowerReportPowerUpFailed )
Power Pol state: 56e ( WdfDevStatePwrPolDevicePowerRequestFailed )

Any advice on this is highly appreciated.

Thanks,
DaveH

send down the Sx irp after you have brought the device back into D0, armed
for wake and then down back to Dx. remember that Sx/S0 transitions hold the
same global kernel lock that controls pnp state, so a parent could fail to
power up and still be around while the children are powering up. it is up
to the driver itself to fail a power up request in the child if the parent's
state is important.

d

--
Please do not send e-mail directly to this alias. this alias is for
newsgroup purposes only.
This posting is provided "AS IS" with no warranties, and confers no rights.


"DaveH" <DaveH@discussions.microsoft.com> wrote in message
news04296C0-F416-42CD-8B3E-3530324DA3BD@microsoft.com...