On Tue, 18 Oct 2011, Ajaykumar Hotchandani wrote: > On 10/13/2011 08:00 PM, Stefano Stabellini wrote: > > On Mon, 10 Oct 2011, Ajaykumar Hotchandani wrote: > >> On 10/06/2011 09:47 PM, Stefano Stabellini wrote: > >>> On Thu, 6 Oct 2011, Yinghai Lu wrote: > >>>> On Thu, Oct 6, 2011 at 3:39 AM, Stefano Stabellini > >>>> <stefano.stabellini@xxxxxxxxxxxxx> wrote: > >>>>> I had the same issue and sent a patch a while ago to fix it, adding > >>>>> > >>>>> current_state = PCI_D0 in acpiphp_glue.c:register_slot > >>>>> > >>>>> it is strange that this does not work for you: > >>>>> > >>>>> http://marc.info/?l=linux-kernel&m=129891002722845&w=2 > >>>> So guest os has to load acpiphp instead of pciehp? > >>> maybe pciehp needs to make sure that current_state = D0 in > >>> pciehp_enable_slot, like acpiphp does > >> Here, acpi hotplugging is involved. > >> With your change in register_slot(), device will have proper power state when module is being loaded for the first time after booting. > >> However, while unload of pci module; following is in pci_device_remove(): > >> if (pci_dev->current_state == PCI_D0) > >> pci_dev->current_state = PCI_UNKNOWN; > >> > >> So, device power state state will remain PCI_UNKNOWN while module is loaded again. Subsequently, MSI write will do nothing. > > Does this mean that this bug would actually trigger even with devices that > > do support _EJ0 and power management? > Nope. I don't have system to verify. But, for the scenario you mentioned > (device is hot pluggable, acpi bus power manageable and device with > pm_cap supported; if I understand it correctly), following is what I > think should happen: > - Inside pci_platform_power_transition(), > platform_pci_power_manageable() will be successful. However, > platform_pci_set_power_state() will fail (as device supports EJ0) and > subsequently pci_update_current_state() will not get called. > - So, current power state of device will not be read and power state of > device will remain PCI_UNKNOWN. > - Now, pci_raw_set_power_state() will get called. Here, as current power > state is PCI_UNKNOWN, pci_write_config_word() will be called with pmcsr > value as 0. As, last two bits of pmcsr is 0, written power state of > device will be PCI_D0 now. And subsequently, dev->current_state will be > assigned as PCI_D0 (by using pci_read_config_word() ). OK, I understand. > > Because acpi_pci_set_power_state won't set current_state to PCI_D0 > > because the "hotplug driver will take care of _PSx" (see > > 10b3dcae0f275e2546e55303d64ddbb58cec7599) but the hotplug driver is not > > actually invoked when loading again a driver module of an existing pci > > device (the example you mention above)? > Can you please elaborate more on this? > acpi_bus_set_power() will update state of acpi_dev (ACPI_STATE_XX) and > not pci_dev (PCI_XX). > And here, issue lies with current_state of pci_dev. I agree, I was merely stating again what the problem is. BTW I am OK with your patch. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
