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

[Mika Westerberg]

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 

Reviewed-by: Mika Westerberg 

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

[Andy Shevchenko]

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 
Signed-off-by: Andy Shevchenko 
---
 arch/powerpc/kernel/pci-hotplug.c | 17 -
 1 file changed, 12 insertions(+), 5 deletions(-)

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);
 }
-- 
2.14.2