[PATCH v1 08/11] PCI/PM: Do not restore BARs if device is not in D0

Rafael J. Wysocki
2022-05-05T18:29:00Z

Do not attempt to restore the device's BARs in
pci_set_full_power_state() if the actual current
power state of the device is not D0.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/pci/pci.c | 32 ++++++++++++++++----------------
1 file changed, 16 insertions(+), 16 deletions(-)

Index: linux-pm/drivers/pci/pci.c
===================================================================
--- linux-pm.orig/drivers/pci/pci.c
+++ linux-pm/drivers/pci/pci.c
@@ -1273,25 +1273,25 @@ static int pci_set_full_power_state(stru

pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
dev->current_state = pmcsr & PCI_PM_CTRL_STATE_MASK;
- if (dev->current_state != PCI_D0)
+ if (dev->current_state != PCI_D0) {
pci_info_ratelimited(dev, "Refused to change power state from %s to D0\n",
pci_power_name(dev->current_state));
-
- /*
- * According to section 5.4.1 of the "PCI BUS POWER MANAGEMENT
- * INTERFACE SPECIFICATION, REV. 1.2", a device transitioning
- * from D3hot to D0 _may_ perform an internal reset, thereby
- * going to "D0 Uninitialized" rather than "D0 Initialized".
- * For example, at least some versions of the 3c905B and the
- * 3c556B exhibit this behaviour.
- *
- * At least some laptop BIOSen (e.g. the Thinkpad T21) leave
- * devices in a D3hot state at boot. Consequently, we need to
- * restore at least the BARs so that the device will be
- * accessible to its driver.
- */
- if (ret > 0)
+ } else if (ret > 0) {
+ /*
+ * According to section 5.4.1 of the "PCI BUS POWER MANAGEMENT
+ * INTERFACE SPECIFICATION, REV. 1.2", a device transitioning
+ * from D3hot to D0 _may_ perform an internal reset, thereby
+ * going to "D0 Uninitialized" rather than "D0 Initialized".
+ * For example, at least some versions of the 3c905B and the
+ * 3c556B exhibit this behaviour.
+ *
+ * At least some laptop BIOSen (e.g. the Thinkpad T21) leave
+ * devices in a D3hot state at boot. Consequently, we need to
+ * restore at least the BARs so that the device will be
+ * accessible to its driver.
+ */
pci_restore_bars(dev);
+ }

if (dev->bus->self)
pcie_aspm_pm_state_change(dev->bus->self);