On Mon, Apr 04, 2022 at 05:41:13PM +0200, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > In theory, pci_power_up() may leave a device in D0-uninitialized > during a transition from D3cold to D0. > > Say, a PCIe device depending on some ACPI power resources is put into > D3cold, so the power resources in question are all turned off. Then, > pci_power_up() is called to put it into D0. > > It first calls pci_platform_power_transition() which invokes > platform_pci_set_power_state() to turn on the ACPI power resources > depended on by the device and, if that is successful, it calls > pci_update_current_state() to update the current_state field of > the PCI device object. If the device's configuration space is > accessible at this point, which is the case if > platform_pci_set_power_state() leaves it in D0-uninitialized (and > there's nothing to prevent it from doing so), current_state will be > set to PCI_D0 and the pci_raw_set_power_state() called subsequently > will notice that the device is in D0 already and do nothing. > However, that is not correct, because it may be still necessary to > restore the device's BARs at this point. > > To address this issue, set current_state temporarily to PCI_D3hot > in the cases in which pci_raw_set_power_state() may need to do more > than just changing the power state of the device. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
