PCI: Split out pci_dev lock/unlock and save/restore

Only cosmetic code changes to existing paths.  Expand the comment in
the new pci_dev_save_and_disable() function since there's a lot
hidden in that Command register write.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 38 insertions, 17 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 9407aabc77a3..d48d9febc241 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3317,22 +3317,49 @@ done:
         return rc;
 }
 
+static void pci_dev_lock(struct pci_dev *dev)
+{
+        pci_cfg_access_lock(dev);
+        /* block PM suspend, driver probe, etc. */
+        device_lock(&dev->dev);
+}
+
+static void pci_dev_unlock(struct pci_dev *dev)
+{
+        device_unlock(&dev->dev);
+        pci_cfg_access_unlock(dev);
+}
+
+static void pci_dev_save_and_disable(struct pci_dev *dev)
+{
+        pci_save_state(dev);
+        /*
+         * Disable the device by clearing the Command register, except for
+         * INTx-disable which is set.  This not only disables MMIO and I/O port
+         * BARs, but also prevents the device from being Bus Master, preventing
+         * DMA from the device including MSI/MSI-X interrupts.  For PCI 2.3
+         * compliant devices, INTx-disable prevents legacy interrupts.
+         */
+        pci_write_config_word(dev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE);
+}
+
+static void pci_dev_restore(struct pci_dev *dev)
+{
+        pci_restore_state(dev);
+}
+
 static int pci_dev_reset(struct pci_dev *dev, int probe)
 {
         int rc;
 
-        if (!probe) {
-                pci_cfg_access_lock(dev);
-                /* block PM suspend, driver probe, etc. */
-                device_lock(&dev->dev);
-        }
+        if (!probe)
+                pci_dev_lock(dev);
 
         rc = __pci_dev_reset(dev, probe);
 
-        if (!probe) {
-                device_unlock(&dev->dev);
-                pci_cfg_access_unlock(dev);
-        }
+        if (!probe)
+                pci_dev_unlock(dev);
+
         return rc;
 }
 /**
@@ -3423,17 +3450,11 @@ int pci_reset_function(struct pci_dev *dev)
         if (rc)
                 return rc;
 
-        pci_save_state(dev);
-
-        /*
-         * both INTx and MSI are disabled after the Interrupt Disable bit
-         * is set and the Bus Master bit is cleared.
-         */
-        pci_write_config_word(dev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE);
+        pci_dev_save_and_disable(dev);
 
         rc = pci_dev_reset(dev, 0);
 
-        pci_restore_state(dev);
+        pci_dev_restore(dev);
 
         return rc;
 }