PCI: Configure ASPM when enabling device

We can't do ASPM configuration at enumeration-time because enabling it
makes some defective hardware unresponsive, even if ASPM is disabled later
(see 41cd766b ("PCI: Don't enable aspm before drivers have had a chance
to veto it").  Therefore, we have to do it after a driver claims the
device.

We previously configured ASPM in pci_set_power_state(), but that's not a
very good place because it's not really related to setting the PCI device
power state, and doing it there means:

  - We incorrectly skipped ASPM config when setting a device that's
    already in D0 to D0.

  - We unnecessarily configured ASPM when setting a device to a low-power
    state (the ASPM feature only applies when the device is in D0).

  - We unnecessarily configured ASPM when called from a .resume() method
    (ASPM configuration needs to be restored during resume, but
    pci_restore_pcie_state() should already do this).

Move ASPM configuration from pci_set_power_state() to
do_pci_enable_device() so we do it when a driver enables a device.

[bhelgaas: changelog]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=79621
Fixes: db288c9c ("PCI / PM: restore the original behavior of pci_set_power_state()")
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Vidya Sagar <sagar.tv@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v3.6+

drivers/pci/pci.c

@@ -839,12 +839,6 @@ int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
 
 	if (!__pci_complete_power_transition(dev, state))
 		error = 0;
-	/*
-	 * When aspm_policy is "powersave" this call ensures
-	 * that ASPM is configured.
-	 */
-	if (!error && dev->bus->self)
-		pcie_aspm_powersave_config_link(dev->bus->self);
 
 	return error;
 }
@@ -1195,12 +1189,18 @@ int __weak pcibios_enable_device(struct pci_dev *dev, int bars)
 static int do_pci_enable_device(struct pci_dev *dev, int bars)
 {
 	int err;
+	struct pci_dev *bridge;
 	u16 cmd;
 	u8 pin;
 
 	err = pci_set_power_state(dev, PCI_D0);
 	if (err < 0 && err != -EIO)
 		return err;
+
+	bridge = pci_upstream_bridge(dev);
+	if (bridge)
+		pcie_aspm_powersave_config_link(bridge);
+
 	err = pcibios_enable_device(dev, bars);
 	if (err < 0)
 		return err;