On Monday, April 09, 2012, Huang Ying wrote: > On Mon, 2012-04-09 at 01:41 +0200, Rafael J. Wysocki wrote: > > > > > > > > If _PS3 is present, then _PR3 may or may not be present. In the latter case > > > > we can only execute _PS3 in the hope it does the right thing, but as long > > > > as we restore the device's configuration registers while resuming it (which is > > > > done by all of our PCI device resume callback routines as far as I can say), > > > > the only possible difference is the resume latency (which may be greater if > > > > power is removed from the device entirely). > > > > > > Another difference between D3Hot and D3Cold for PCI devices is config > > > space availability. That is, in D3Hot, you can access D3Hot, while in > > > D3Cold you can not do that. For example, PME poll logic need to be > > > disabled if we put device into D3Cold. > > > > We're not talking about PCI here. PCI D3hot/D3cold is actually well defined, > > while the ACPI "couterparts" aren't. And BTW I know the properties of the PCI > > power management states. :-) > > I see. > > > > > However, in that case we shouldn't > > > > turn off the device's power resources after _PS3 has been executed (if we > > > > turned them off, power would be removed from the device, which wouldn't be > > > > what PCI wanted). So, to handle this particular case we need to pass > > > > ACPI_STATE_D3_HOT to acpi_bus_set_power(), meaning "avoid going into D3_cold, > > > > if possible". > > > > > > > > In both _PS3 and _PR3 are present, we should evaluate _PS3 and then turn off > > > > the power resources listed as "off" by _PR3 (and turn on the power resoruces > > > > listed by it as "on"), but we need to restore the configuration registers of > > > > the device while resuming it. I think this is handled correctly without > > > > modifications. > > > > > > > > If neither _PS3 nor _PR3 is present, we shouldn't turn off the device's > > > > power resources, because PCI doesn't want power to be removed from the device. > > > > > > For PCI device plugged into system via slot (not integrated into PCH > > > or motherboard), there is no ACPI handle associate with it, so that > > > there are neither _PS3 nor _PR3 presented. But it is still possible > > > to turn off the device power via the associated PCIe port, which has > > > _PS3 and/or _PR3 presented. I think that situation is reasonable too. > > > > Again, this hasn't anything to do with ACPI. > > > > We're discussing standard interfaces exposed by ACPI. That is, if I say > > "to turn of the device's power resources" I mean to call _OFF for all of the > > power resources listed by _PR0 for that device. Nothing more or less than > > that. > > > > > > In summary, if PCI wants the device to be put into PCI_D3hot and _PS3 is > > > > present, we should evaluate _PS3. However, we shouldn't turn the device's > > > > power resources off unless _PR3 is present, in which case we can turn off > > > > the power resources listed by it as "off". > > > > > > How to turn the device's power resources off without _PR3? It may be > > > possible via PCIe port as I said above. Do you mean that? Or > > > something else? > > > > If _PR0 is present, it returns the list of power resources needed by the > > device. If you turn them all off, the assumption is that power has been > > removed from the device, so it is in D3(cold). > > So. If PCI wants the device to be put into PCI_D3hot and _PS3 is > present. We should evaluate _PS3 AND set the pci_dev->current_state to > PCI_D3cold? No, I believe we should use the standard PCI PM interface to put the device into PCI_D3hot and skip the execution of _PS3 (which is not what we do now, but that's only because acpi_pci_set_power_state() doesn't distinguish ACPI D3_hot from ACPI D3_cold). If the standard PCI PM interface is not supported, the PCI_D3hot state is not well defined for the device. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
