CSIT-1043: Execute pci rescan only if needed

Pci rescan is a rather invasive process, which is why it should be
executed only if needed. This patch moves the pci rescan after
pci device driver discovery, rescanning the devices for further attemps
at driver discovery.

Change-Id: I29c939b44c3f67371416a99c711e057f711ba9b4
Signed-off-by: juraj.linkes <juraj.linkes@pantheon.tech>

1 files changed, 24 insertions, 7 deletions

diff --git a/resources/libraries/python/DUTSetup.py b/resources/libraries/python/DUTSetup.py
index d08704bba1..5e07ee0e7a 100644
--- a/resources/libraries/python/DUTSetup.py
+++ b/resources/libraries/python/DUTSetup.py
@@ -385,24 +385,31 @@ class DUTSetup(object):
     def get_pci_dev_driver(node, pci_addr):
         """Get current PCI device driver on node.
 
+        .. note::
+            # lspci -vmmks 0000:00:05.0
+            Slot:   00:05.0
+            Class:  Ethernet controller
+            Vendor: Red Hat, Inc
+            Device: Virtio network device
+            SVendor:        Red Hat, Inc
+            SDevice:        Device 0001
+            PhySlot:        5
+            Driver: virtio-pci
+
         :param node: DUT node.
         :param pci_addr: PCI device address.
         :type node: dict
         :type pci_addr: str
         :returns: Driver or None
         :raises RuntimeError: If PCI rescan or lspci command execution failed.
+        :raises RuntimeError: If it is not possible to get the interface driver
+            information from the node.
         """
         ssh = SSH()
         ssh.connect(node)
 
         for i in range(3):
-            logger.trace('Try {0}: Get interface driver'.format(i))
-            cmd = 'sh -c "echo 1 > /sys/bus/pci/rescan"'
-            ret_code, _, _ = ssh.exec_command_sudo(cmd)
-            if int(ret_code) != 0:
-                raise RuntimeError("'{0}' failed on '{1}'"
-                                   .format(cmd, node['host']))
-
+            logger.trace('Try number {0}: Get PCI device driver'.format(i))
             cmd = 'lspci -vmmks {0}'.format(pci_addr)
             ret_code, stdout, _ = ssh.exec_command(cmd)
             if int(ret_code) != 0:
@@ -421,6 +428,16 @@ class DUTSetup(object):
                         return None
                 if name == 'Driver:':
                     return value
+
+            if i < 2:
+                logger.trace('Driver for PCI device {} not found, executing '
+                             'pci rescan and retrying'.format(pci_addr))
+                cmd = 'sh -c "echo 1 > /sys/bus/pci/rescan"'
+                ret_code, _, _ = ssh.exec_command_sudo(cmd)
+                if int(ret_code) != 0:
+                    raise RuntimeError("'{0}' failed on '{1}'"
+                                       .format(cmd, node['host']))
+
         return None
 
     @staticmethod