[PATCH] PCI: generic: Fix address window calculation for non-zero starting bus.

[David Daney <ddaney.cavm@gmail.com>]

From: David Daney <david.daney@cavium.com>

Make the offset from the beginning of the "reg" property be from the
starting bus number, rather than zero.  Hoist the invariant size
calculation out of the mapping for loop.

Update host-generic-pci.txt to clarify the semantics of the "reg"
property with respect to non-zero starting bus numbers.

Signed-off-by: David Daney <david.daney@cavium.com>
---
This is a replacement for:

https://lkml.org/lkml/2015/10/2/653

Since that patch is getting too much push-back, this is the only other
option for fixing the driver to be internally consistent in its
treatment of the offset from "reg" to the first bus in the "bus-range"
property.

 Documentation/devicetree/bindings/pci/host-generic-pci.txt | 5 +++--
 drivers/pci/host/pci-host-generic.c                        | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/pci/host-generic-pci.txt b/Documentation/devicetree/bindings/pci/host-generic-pci.txt
index cf3e205..3f1d3fc 100644
--- a/Documentation/devicetree/bindings/pci/host-generic-pci.txt
+++ b/Documentation/devicetree/bindings/pci/host-generic-pci.txt
@@ -34,8 +34,9 @@ Properties of the host controller node:
 - #size-cells    : Must be 2.
 
 - reg            : The Configuration Space base address and size, as accessed
-                   from the parent bus.
-
+                   from the parent bus.  The base address corresponds to
+                   the first bus in the "bus-range" property.  If no
+                   "bus-range" is specified, this will be bus 0 (the default).
 
 Properties of the /chosen node:
 
diff --git a/drivers/pci/host/pci-host-generic.c b/drivers/pci/host/pci-host-generic.c
index fe9a81b..bb93346 100644
--- a/drivers/pci/host/pci-host-generic.c
+++ b/drivers/pci/host/pci-host-generic.c
@@ -169,6 +169,7 @@ static int gen_pci_parse_map_cfg_windows(struct gen_pci *pci)
 	struct resource *bus_range;
 	struct device *dev = pci->host.dev.parent;
 	struct device_node *np = dev->of_node;
+	u32 sz = 1 << pci->cfg.ops->bus_shift;
 
 	err = of_address_to_resource(np, 0, &pci->cfg.res);
 	if (err) {
@@ -196,10 +197,9 @@ static int gen_pci_parse_map_cfg_windows(struct gen_pci *pci)
 	bus_range = pci->cfg.bus_range;
 	for (busn = bus_range->start; busn <= bus_range->end; ++busn) {
 		u32 idx = busn - bus_range->start;
-		u32 sz = 1 << pci->cfg.ops->bus_shift;
 
 		pci->cfg.win[idx] = devm_ioremap(dev,
-						 pci->cfg.res.start + busn * sz,
+						 pci->cfg.res.start + idx * sz,
 						 sz);
 		if (!pci->cfg.win[idx])
 			return -ENOMEM;
-- 
1.9.1