[U-Boot] [PATCH 05/23] pci: xilinx: Avoid writing memory base or limit registers

[Paul Burton]

Writing the PCI memory base & limit registers leads to the root bridge
reporting a PCI_MEMORY_BASE value of 0 & a PCI_MEMORY_LIMIT value of
0x1600. If we then boot Linux, it sees that the bridge device needs
0x16000000 bytes of memory space & fails to assign it.

It's unclear to me why this happens, and poking values from the shell
doesn't seem to make anything clearer, but this workaround allows a MIPS
Boston board to boot Linux & let Linux successfully probe the PCIe bus &
all devices connected to it.

Signed-off-by: Paul Burton <paul.burton at imgtec.com>
---

 drivers/pci/pcie_xilinx.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/pci/pcie_xilinx.c b/drivers/pci/pcie_xilinx.c
index 9059c41..0237bec 100644
--- a/drivers/pci/pcie_xilinx.c
+++ b/drivers/pci/pcie_xilinx.c
@@ -160,6 +160,15 @@ static int pcie_xilinx_write_config(struct udevice *bus, pci_dev_t bdf,
 	if (err < 0)
 		return 0;
 
+	if (bdf == PCI_BDF(bus->seq, 0, 0)) {
+		switch (offset) {
+		case PCI_MEMORY_BASE:
+		case PCI_MEMORY_LIMIT:
+			/* Writing the memory base or limit causes problems */
+			return 0;
+		}
+	}
+
 	switch (size) {
 	case PCI_SIZE_8:
 		__raw_writeb(value, address);
-- 
2.10.0