Re: [Xen-devel] Re: [RFC PATCH] set current_state to D0 inregister_slot

[Ian Campbell]

On Tue, 2011-03-08 at 14:50 +0000, Ian Campbell wrote:
> On Fri, 2011-03-04 at 18:42 +0000, Jesse Barnes wrote:
> > On Mon, 28 Feb 2011 16:20:11 +0000
> > Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > 
> > > Hi all,
> > > if a device doesn't support power management (pm_cap == 0) but it is
> > > acpi_pci_power_manageable() because there is a _PS0 method declared for
> > > it and _EJ0 is also declared for the slot then nobody is going to set
> > > current_state = PCI_D0 for this device.  This is what I think it is
> > > happening:
> > > 
> > > 
> > > pci_enable_device
> > >     |
> > > __pci_enable_device_flags
> > > /* here we do not set current_state because !pm_cap */
> > >     |
> > > do_pci_enable_device
> > >     |
> > > pci_set_power_state
> > >     |
> > > __pci_start_power_transition
> > >     |
> > > pci_platform_power_transition
> > > /* platform_pci_power_manageable() calls acpi_pci_power_manageable that
> > >  * returns true */
> > >     |
> > > platform_pci_set_power_state
> > > /* acpi_pci_set_power_state gets called and does nothing because the
> > >  * acpi device has _EJ0, see the comment "If the ACPI device has _EJ0,
> > >  * ignore the device" */
> > > 
> > > 
> > > at this point if we refer to the commit message that introduced the
> > > comment above (10b3dcae0f275e2546e55303d64ddbb58cec7599), it is up to
> > > the hotplug driver to set the state to D0.
> > > However AFAICT the pci hotplug driver never does, in fact
> > > drivers/pci/hotplug/acpiphp_glue.c:register_slot sets the slot flags to
> > > (SLOT_ENABLED | SLOT_POWEREDON) but it does not set the pci device
> > > current state to PCI_D0.
> > > 
> > > So my proposed fix is also to set current_state = PCI_D0 in
> > > register_slot.
> > > Comments are very welcome.
> > > 
> > > 
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > 
> > Yeah, looks fine.  ACPIPHP is happy for the attention. :)
> 
> This helps for coldplug of devices which lack the PCI CFG space power
> management capability but doesn't help with hotplugging such devices.
> 
> Is it fair to assume that any PCI device in a slot which has just been
> powered on will be in D0?
> 
> e.g. Stefano's patch plus the following seem to fix the crashes I've
> been having with 82599 VFs for both hot and cold plug.
> 
> Ian.
> 
> acpiphp: set each new function to state D0 after powering on a slot.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

That version did it too soon and/or to devices which were already known.
I think this one is more like it:

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