PCI: Open-code the two pass loop when scanning bridges

The current scanning code is really hard to understand because it calls
the same function in a loop where pass value is changed without any
comments explaining it:

  for (pass = 0; pass < 2; pass++)
    for_each_pci_bridge(dev, bus)
      max = pci_scan_bridge(bus, dev, max, pass);

Unfamiliar reader cannot tell easily what is the purpose of this loop
without looking at internals of pci_scan_bridge().

In order to make this bit easier to understand, open-code the loop in
pci_scan_child_bus() and pci_hp_add_bridge() with added comments.

No functional changes intended.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 20 insertions, 7 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 62d45a76f663..61813938d186 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2398,7 +2398,7 @@ void __weak pcibios_fixup_bus(struct pci_bus *bus)
 
 unsigned int pci_scan_child_bus(struct pci_bus *bus)
 {
-        unsigned int devfn, pass, max = bus->busn_res.start;
+        unsigned int devfn, max = bus->busn_res.start;
         struct pci_dev *dev;
 
         dev_dbg(&bus->dev, "scanning bus\n");
@@ -2420,9 +2420,17 @@ unsigned int pci_scan_child_bus(struct pci_bus *bus)
                 bus->is_added = 1;
         }
 
-        for (pass = 0; pass < 2; pass++)
-                for_each_pci_bridge(dev, bus)
-                        max = pci_scan_bridge(bus, dev, max, pass);
+        /*
+         * Scan bridges that are already configured. We don't touch them
+         * unless they are misconfigured (which will be done in the second
+         * scan below).
+         */
+        for_each_pci_bridge(dev, bus)
+                max = pci_scan_bridge(bus, dev, max, 0);
+
+        /* Scan bridges that need to be reconfigured */
+        for_each_pci_bridge(dev, bus)
+                max = pci_scan_bridge(bus, dev, max, 1);
 
         /*
          * Make sure a hotplug bridge has at least the minimum requested
@@ -2739,7 +2747,7 @@ void __init pci_sort_breadthfirst(void)
 int pci_hp_add_bridge(struct pci_dev *dev)
 {
         struct pci_bus *parent = dev->bus;
-        int pass, busnr, start = parent->busn_res.start;
+        int busnr, start = parent->busn_res.start;
         int end = parent->busn_res.end;
 
         for (busnr = start; busnr <= end; busnr++) {
@@ -2750,8 +2758,13 @@ int pci_hp_add_bridge(struct pci_dev *dev)
                 dev_err(&dev->dev, "No bus number available for hot-added bridge\n");
                 return -1;
         }
-        for (pass = 0; pass < 2; pass++)
-                busnr = pci_scan_bridge(parent, dev, busnr, pass);
+
+        /* Scan bridges that are already configured */
+        busnr = pci_scan_bridge(parent, dev, busnr, 0);
+
+        /* Scan bridges that need to be reconfigured */
+        pci_scan_bridge(parent, dev, busnr, 1);
+
         if (!dev->subordinate)
                 return -1;