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Subject[PATCH v2 2/8] PCI: Open-code the two pass loop when scanning bridges
Date
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>
---
drivers/pci/probe.c | 27 ++++++++++++++++++++-------
1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 7302cef51d3f..107052f1dad9 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++) {
@@ -2751,8 +2759,13 @@ int pci_hp_add_bridge(struct pci_dev *dev)
pci_name(dev));
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;

--
2.14.2
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