PCI: reset pci device state to unknown state for resume

Considering below scenario:
1.Unload a PCI device's driver, the device ->current remains in PCI_D0.
2.Do suspend/resume circle. After that, BIOS puts the device to D3.
3.Reload the device driver. The calling pci_set_power_state in the
driver can't change the state to D0, as set_power_state thinks the
device is already in D0.

A bug is reported at http://bugzilla.kernel.org/show_bug.cgi?id=6024
Pat attached a patch at
http://marc.theaimsgroup.com/?l=linux-pci&m=114049761428561&w=2 for this
issue, but it's lost. As pci_set_power_state can handle D3 -> D0
correctly (restore config space), I simplified Patrick's patch.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Cc: Patrick Mochel <mochel@digitalimplant.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index b1c0c707d96c..194f1d21d3d7 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -265,6 +265,13 @@ static int pci_device_remove(struct device * dev)
         }
 
         /*
+         * If the device is still on, set the power state as "unknown",
+         * since it might change by the next time we load the driver.
+         */
+        if (pci_dev->current_state == PCI_D0)
+                pci_dev->current_state = PCI_UNKNOWN;
+
+        /*
          * We would love to complain here if pci_dev->is_enabled is set, that
          * the driver should have called pci_disable_device(), but the
          * unfortunate fact is there are too many odd BIOS and bridge setups
@@ -288,6 +295,12 @@ static int pci_device_suspend(struct device * dev, pm_message_t state)
                 suspend_report_result(drv->suspend, i);
         } else {
                 pci_save_state(pci_dev);
+                /*
+                 * mark its power state as "unknown", since we don't know if
+                 * e.g. the BIOS will change its device state when we suspend.
+                 */
+                if (pci_dev->current_state == PCI_D0)
+                        pci_dev->current_state = PCI_UNKNOWN;
         }
         return i;
 }