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+

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 60230da..3972819 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1226,6 +1226,10 @@ static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
  *
  * On success, return 0 or 1, depending on whether or not it is necessary to
  * restore the device's BARs subsequently (1 is returned in that case).
+ *
+ * On failure, return a negative error code.  Always return failure if @dev
+ * lacks a Power Management Capability, even if the platform was able to
+ * put the device in D0 via non-PCI means.
  */
 int pci_power_up(struct pci_dev *dev)
 {
@@ -1242,9 +1246,6 @@ int pci_power_up(struct pci_dev *dev)
                else
                        dev->current_state = state;
 
-               if (state == PCI_D0)
-                       return 0;
-
                return -EIO;
        }
 
@@ -1302,8 +1303,12 @@ static int pci_set_full_power_state(struct pci_dev *dev)
        int ret;
 
        ret = pci_power_up(dev);
-       if (ret < 0)
+       if (ret < 0) {
+               if (dev->current_state == PCI_D0)
+                       return 0;
+
                return ret;
+       }
 
        pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
        dev->current_state = pmcsr & PCI_PM_CTRL_STATE_MASK;