[U-Boot] [RFC PATCH 07/29] drivers: pci-uclass: add support for Enhanced Allocation in Bridges

[Suneel Garapati]

From: Suneel Garapati <sgarapati at marvell.com>

If Enhanced Allocation capability is present in bridges, use it
to read the fixed sub-ordinate bus number.

Signed-off-by: Suneel Garapati <sgarapati at marvell.com>
---
 drivers/pci/pci-uclass.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/pci-uclass.c b/drivers/pci/pci-uclass.c
index f17e83565c..51f7135723 100644
--- a/drivers/pci/pci-uclass.c
+++ b/drivers/pci/pci-uclass.c
@@ -599,10 +599,20 @@ int dm_pci_hose_probe_bus(struct udevice *bus)
 {
 	int sub_bus;
 	int ret;
+	int ea_pos;
+	u8 reg;
 
 	debug("%s\n", __func__);
 
-	sub_bus = pci_get_bus_max() + 1;
+	ea_pos = dm_pci_find_capability(bus, PCI_CAP_ID_EA);
+
+	if (ea_pos) {
+		dm_pci_read_config8(bus, ea_pos + sizeof(u32) + sizeof(u8),
+				    &reg);
+		sub_bus = reg;
+	} else {
+		sub_bus = pci_get_bus_max() + 1;
+	}
 	debug("%s: bus = %d/%s\n", __func__, sub_bus, bus->name);
 	dm_pciauto_prescan_setup_bridge(bus, sub_bus);
 
@@ -612,12 +622,15 @@ int dm_pci_hose_probe_bus(struct udevice *bus)
 		      ret);
 		return ret;
 	}
-	if (sub_bus != bus->seq) {
-		printf("%s: Internal error, bus '%s' got seq %d, expected %d\n",
-		       __func__, bus->name, bus->seq, sub_bus);
-		return -EPIPE;
+
+	if (!ea_pos) {
+		if (sub_bus != bus->seq) {
+			printf("%s: Internal error, bus '%s' got seq %d, expected %d\n",
+			       __func__, bus->name, bus->seq, sub_bus);
+			return -EPIPE;
+		}
+		sub_bus = pci_get_bus_max();
 	}
-	sub_bus = pci_get_bus_max();
 	dm_pciauto_postscan_setup_bridge(bus, sub_bus);
 
 	return sub_bus;
-- 
2.23.0