[PATCH 3/3] PCI: generic: Add support for Cavium ThunderX PCIe root complexes.

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

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

The config space for external PCIe root complexes on some Cavium
ThunderX SoCs is very similar to CAM and ECAM, but differs in the
shift values that have to be applied to the bus and devfn numbers to
compose that address window offset.  These root complexes also have
the interesting property that there is no root bridge, so the standard
manner of limiting scanning to only the first device doesn't work.  We
can use the standard pci-host-generic driver if we make a minor
addition to handle these differences, so we...

Add a mapping function for ThunderX PCIe root complexes with a bus
shift of 24 and devfn shift of 16.  Ignore accesses for devices other
than the first device on the primary bus.

Document the whole thing in devicetree/bindings/pci/host-generic-pci.txt

Signed-off-by: David Daney <david.daney@cavium.com>
---
 .../devicetree/bindings/pci/host-generic-pci.txt   |  8 +++---
 drivers/pci/host/pci-host-generic.c                | 29 ++++++++++++++++++++++
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/pci/host-generic-pci.txt b/Documentation/devicetree/bindings/pci/host-generic-pci.txt
index 105a968..a5aed0f 100644
--- a/Documentation/devicetree/bindings/pci/host-generic-pci.txt
+++ b/Documentation/devicetree/bindings/pci/host-generic-pci.txt
@@ -14,9 +14,11 @@ tree bindings communicated in pci.txt:
 
 Properties of the host controller node:
 
-- compatible     : Must be "pci-host-cam-generic" or "pci-host-ecam-generic"
-                   depending on the layout of configuration space (CAM vs
-                   ECAM respectively).
+- compatible     : One of the following with bus:devfn:reg mapped to the
+                   PCI config space address window in the bit positions shown:
+                   "pci-host-cam-generic" -- 'CAM'  bits 16:8:0
+                   "pci-host-ecam-generic" -- 'ECAM'  bits 20:12:0
+                   "cavium,pci-host-thunder-pem" --  bits 24:16:0
 
 - device_type    : Must be "pci".
 
diff --git a/drivers/pci/host/pci-host-generic.c b/drivers/pci/host/pci-host-generic.c
index e364232..e1d8d5b 100644
--- a/drivers/pci/host/pci-host-generic.c
+++ b/drivers/pci/host/pci-host-generic.c
@@ -91,6 +91,32 @@ static struct gen_pci_cfg_bus_ops gen_pci_cfg_ecam_bus_ops = {
 	}
 };
 
+static void __iomem *gen_pci_map_cfg_bus_thunder_pem(struct pci_bus *bus,
+						     unsigned int devfn,
+						     int where)
+{
+	struct gen_pci *pci = bus->sysdata;
+	resource_size_t idx = bus->number - pci->cfg.bus_range->start;
+
+	/*
+	 * Thunder PEM is a PCIe RC, but without a root bridge.  On
+	 * the primary bus, ignore accesses for devices other than
+	 * the first device.
+	 */
+	if (idx == 0 && (devfn & ~7u))
+		return NULL;
+	return pci->cfg.win[idx] + ((devfn << 16) | where);
+}
+
+static struct gen_pci_cfg_bus_ops gen_pci_cfg_thunder_pem_bus_ops = {
+	.bus_shift	= 24,
+	.ops		= {
+		.map_bus	= gen_pci_map_cfg_bus_thunder_pem,
+		.read		= pci_generic_config_read,
+		.write		= pci_generic_config_write,
+	}
+};
+
 static const struct of_device_id gen_pci_of_match[] = {
 	{ .compatible = "pci-host-cam-generic",
 	  .data = &gen_pci_cfg_cam_bus_ops },
@@ -98,6 +124,9 @@ static const struct of_device_id gen_pci_of_match[] = {
 	{ .compatible = "pci-host-ecam-generic",
 	  .data = &gen_pci_cfg_ecam_bus_ops },
 
+	{ .compatible = "cavium,pci-host-thunder-pem",
+	  .data = &gen_pci_cfg_thunder_pem_bus_ops },
+
 	{ },
 };
 MODULE_DEVICE_TABLE(of, gen_pci_of_match);
-- 
1.9.1