[PATCH v3 04/12] pci: xilinx: Avoid writing memory base/limit for root bridge

[Uros Stajic]

From: Chao-ying Fu <cfu at mips.com>

Avoid writing to PCI_MEMORY_BASE and PCI_MEMORY_LIMIT registers for
bus 0, device 0 (the root bridge) in the Xilinx PCIe driver.

On platforms such as the MIPS Boston board, writing to these fields
results in incorrect values (e.g. base = 0x0, limit = 0x1600), which
causes Linux to fail PCIe memory space assignment.

As a result, Linux can boot successfully and probe the PCIe bus and
all connected devices on platforms like the MIPS Boston board.

Signed-off-by: Chao-ying Fu <cfu at mips.com>
Signed-off-by: Uros Stajic <uros.stajic at htecgroup.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 63058e8e7c5..4ef20474a0b 100644
--- a/drivers/pci/pcie_xilinx.c
+++ b/drivers/pci/pcie_xilinx.c
@@ -132,6 +132,15 @@ static int pcie_xilinx_write_config(struct udevice *bus, pci_dev_t bdf,
 				    uint offset, ulong value,
 				    enum pci_size_t size)
 {
+	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;
+		}
+	}
+
 	return pci_generic_mmap_write_config(bus, pcie_xilinx_config_address,
 					     bdf, offset, value, size);
 }
-- 
2.34.1