[v2,2/2] powerpc/pci: Unroll two pass loop when scanning bridges

Message ID 20171110175230.82522-2-andriy.shevchenko@linux.intel.com
State New
Headers show
Series
  • [v2,1/2] powerpc/pci: convert to use for_each_pci_bridge() helper
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Commit Message

Andy Shevchenko Nov. 10, 2017, 5:52 p.m.
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.

Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 arch/powerpc/kernel/pci-hotplug.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

Comments

Mika Westerberg Nov. 13, 2017, 2:30 p.m. | #1
On Fri, Nov 10, 2017 at 07:52:30PM +0200, Andy Shevchenko wrote:
> 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.
> 
> Cc: Mika Westerberg <mika.westerberg@linux.intel.com>

Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Patch

diff --git a/arch/powerpc/kernel/pci-hotplug.c b/arch/powerpc/kernel/pci-hotplug.c
index 741f47295188..cf47b1aec4c2 100644
--- a/arch/powerpc/kernel/pci-hotplug.c
+++ b/arch/powerpc/kernel/pci-hotplug.c
@@ -104,7 +104,7 @@  EXPORT_SYMBOL_GPL(pci_hp_remove_devices);
  */
 void pci_hp_add_devices(struct pci_bus *bus)
 {
-	int slotno, mode, pass, max;
+	int slotno, mode, max;
 	struct pci_dev *dev;
 	struct pci_controller *phb;
 	struct device_node *dn = pci_bus_to_OF_node(bus);
@@ -133,10 +133,17 @@  void pci_hp_add_devices(struct pci_bus *bus)
 		pci_scan_slot(bus, PCI_DEVFN(slotno, 0));
 		pcibios_setup_bus_devices(bus);
 		max = bus->busn_res.start;
-		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);
 	}
 	pcibios_finish_adding_to_bus(bus);
 }