PCI/PM: Only read PCI_PM_CTRL register when available

For a device with no Power Management Capability, pci_power_up() previously
returned 0 (success) if the platform was able to put the device in D0,
which led to pci_set_full_power_state() trying to read PCI_PM_CTRL, even
though it doesn't exist.

Since dev->pm_cap == 0 in this case, pci_set_full_power_state() actually
read the wrong register, interpreted it as PCI_PM_CTRL, and corrupted
dev->current_state.  This led to messages like this in some cases:

  pci 0000:01:00.0: Refused to change power state from D3hot to D0

To prevent this, make pci_power_up() always return a negative failure code
if the device lacks a Power Management Capability, even if non-PCI platform
power management has been able to put the device in D0.  The failure will
prevent pci_set_full_power_state() from trying to access PCI_PM_CTRL.

Fixes: e200904b275c ("PCI/PM: Split pci_power_up()")
Link: https://lore.kernel.org/r/20230824013738.1894965-1-chenfeiyang@loongson.cn
Signed-off-by: Feiyang Chen <chenfeiyang@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: stable@vger.kernel.org	# v5.19+

0 files changed, 0 insertions, 0 deletions