[PATCH v5 1/9] PCI: mediatek: Using slot's devfn for compare to fix mtk_pcie_find_port logic

[honghui.zhang]

From: Honghui Zhang <honghui.zhang@xxxxxxxxxxxx>

The Mediatek's host controller has two slots, each with it's own control
registers. The host driver need to identify which slot was connected
in order to access the device's configuration space. There's problem
for current host driver to find out which slot was connected to for
a given EP device.

Assuming each slot have connect with one EP device as below:

                host bridge
  bus 0 --> __________|_______
           |                  |
           |                  |
         slot 0             slot 1
  bus 1 -->|        bus 2 --> |
           |                  |
         EP 0               EP 1

During PCI enumeration, system software will scan all the PCI device
starting from devfn 0. So it will get the proper port for slot0 and
slot1 device when using PCI_SLOT(devfn) for match. But it will get
the wrong slot for EP1: The devfn will be start from 0 when scanning
EP1 behind slot1, it will get port0 since the PCI_SLOT(EP1) is match
for port0's slot value. So the host driver should not using EP's devfn
but the slot's devfn(the slot which EP was connected to) for match.

This patch fix the mtk_pcie_find_port's logic by using the slot's
devfn for match if finding device connected to the subordinate bus.

Signed-off-by: Honghui Zhang <honghui.zhang@xxxxxxxxxxxx>
---
 drivers/pci/controller/pcie-mediatek.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pcie-mediatek.c b/drivers/pci/controller/pcie-mediatek.c
index 9999dae..264e03f 100644
--- a/drivers/pci/controller/pcie-mediatek.c
+++ b/drivers/pci/controller/pcie-mediatek.c
@@ -337,10 +337,25 @@ static struct mtk_pcie_port *mtk_pcie_find_port(struct pci_bus *bus,
 {
 	struct mtk_pcie *pcie = bus->sysdata;
 	struct mtk_pcie_port *port;
+	struct pci_dev *dev = NULL;
+
+	/*
+	 * Walk the bus hierarchy to get the devfn value
+	 * of the port in the root bus.
+	 */
+	while (bus && bus->number) {
+		dev = bus->self;
+		bus = dev->bus;
+	}
+
+	list_for_each_entry(port, &pcie->ports, list) {
+		/* Using slot's devfn to compare for subordinary bus. */
+		if (dev)
+			devfn = dev->devfn;
 
-	list_for_each_entry(port, &pcie->ports, list)
 		if (port->slot == PCI_SLOT(devfn))
 			return port;
+	}
 
 	return NULL;
 }
-- 
2.6.4