From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com
[ Upstream commit 4514d991d99211f225d83b7e640285f29f0755d0 ]
It should not be necessary to update the current_state field of struct pci_dev in pci_enable_device_flags() before calling do_pci_enable_device() for the device, because none of the code between that point and the pci_set_power_state() call in do_pci_enable_device() invoked later depends on it.
Moreover, doing that is actively harmful in some cases. For example, if the given PCI device depends on an ACPI power resource whose _STA method initially returns 0 ("off"), but the config space of the PCI device is accessible and the power state retrieved from the PCI_PM_CTRL register is D0, the current_state field in the struct pci_dev representing that device will get out of sync with the power.state of its ACPI companion object and that will lead to power management issues going forward.
To avoid such issues it is better to leave the current_state value as is until it is changed to PCI_D0 by do_pci_enable_device() as appropriate. However, the power state of the device is not changed to PCI_D0 if it is already enabled when pci_enable_device_flags() gets called for it, so update its current_state in that case, but use pci_update_current_state() covering platform PM too for that.
Link: https://lore.kernel.org/lkml/20210314000439.3138941-1-luzmaximilian@gmail.co... Reported-by: Maximilian Luz luzmaximilian@gmail.com Tested-by: Maximilian Luz luzmaximilian@gmail.com Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pci/pci.c | 16 +++------------- 1 file changed, 3 insertions(+), 13 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index e09653c73ab4..acd89fa9820c 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1378,20 +1378,10 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) int err; int i, bars = 0;
- /* - * Power state could be unknown at this point, either due to a fresh - * boot or a device removal call. So get the current power state - * so that things like MSI message writing will behave as expected - * (e.g. if the device really is in D0 at enable time). - */ - if (dev->pm_cap) { - u16 pmcsr; - pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr); - dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK); - } - - if (atomic_inc_return(&dev->enable_cnt) > 1) + if (atomic_inc_return(&dev->enable_cnt) > 1) { + pci_update_current_state(dev, dev->current_state); return 0; /* already enabled */ + }
bridge = pci_upstream_bridge(dev); if (bridge)