[linux-pm] [PATCH] PCI PM: Restore standard config registers of all devices early (was: Re: EeePC resume failure - timers)

[Alan Stern]

On Fri, 16 Jan 2009, Rafael J. Wysocki wrote:

> There is a problem in our handling of suspend-resume of PCI devices
> that many of them have their standard config registers restored with
> interrupts enabled and they are put into the full power state with
> interrupts enabled as well.  This may lead to the following scenario:
> * an interrupt vector is shared between two or more devices
> * one device is resumed earlier and generates an interrupt
> * the interrupt handler of another device tries to handle it and
>   attempts to access the device the config space of which hasn't
>   been restored yet and/or which still is in a low power state
> * the system crashes as a result
> 
> To prevent this from happening we should restore the standard
> configuration registers of all devices with interrupts disabled and
> we should put them into the D0 power state right after that.
> Unfortunately, this cannot be done using the existing
> pci_set_power_state(), because it can sleep.  Also, to do it we have
> to make sure that the config spaces of all devices were actually
> saved during suspend.

Alternatively, PCI drivers should be smart enough to realize that a
shared interrupt arriving while their device is suspended could not
possibly be generated by that device.  In such a case the driver can
return IRQ_NONE directly, without ever touching the device.

USB does this.  However I admit that fixing every PCI driver would be a 
big chore...

Alan Stern