1 files changed, 40 insertions, 1 deletions

diff --git a/drivers/pci/host/pci-xgene.c b/drivers/pci/host/pci-xgene.c
index 3e5a636..70af714 100644
--- a/drivers/pci/host/pci-xgene.c
+++ b/drivers/pci/host/pci-xgene.c
@@ -59,6 +59,12 @@
 #define SZ_1T				(SZ_1G*1024ULL)
 #define PIPE_PHY_RATE_RD(src)		((0xc000 & (u32)(src)) >> 0xe)
 
+#define ROOT_CAP_AND_CTRL		0x5C
+
+/* PCIe IP version */
+#define XGENE_PCIE_IP_VER_UNKN		0
+#define XGENE_PCIE_IP_VER_1		1
+
 struct xgene_pcie_port {
 	struct device_node	*node;
 	struct device		*dev;
@@ -67,6 +73,7 @@ struct xgene_pcie_port {
 	void __iomem		*cfg_base;
 	unsigned long		cfg_addr;
 	bool			link_up;
+	u32			version;
 };
 
 static inline u32 pcie_bar_low_val(u32 addr, u32 flags)
@@ -140,9 +147,37 @@ static void __iomem *xgene_pcie_map_bus(struct pci_bus *bus, unsigned int devfn,
 	return xgene_pcie_get_cfg_base(bus) + offset;
 }
 
+static int xgene_pcie_config_read32(struct pci_bus *bus, unsigned int devfn,
+				    int where, int size, u32 *val)
+{
+	struct xgene_pcie_port *port = bus->sysdata;
+
+	if (pci_generic_config_read32(bus, devfn, where & ~0x3, 4, val) !=
+	    PCIBIOS_SUCCESSFUL)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+
+	/*
+	 * The v1 controller has a bug in its Configuration Request
+	 * Retry Status (CRS) logic: when CRS is enabled and we read the
+	 * Vendor and Device ID of a non-existent device, the controller
+	 * fabricates return data of 0xFFFF0001 ("device exists but is not
+	 * ready") instead of 0xFFFFFFFF ("device does not exist").  This
+	 * causes the PCI core to retry the read until it times out.
+	 * Avoid this by not claiming to support CRS.
+	 */
+	if (pci_is_root_bus(bus) && (port->version == XGENE_PCIE_IP_VER_1) &&
+	    ((where & ~0x3) == ROOT_CAP_AND_CTRL))
+		*val &= ~(PCI_EXP_RTCAP_CRSVIS << 16);
+
+	if (size <= 2)
+		*val = (*val >> (8 * (where & 3))) & ((1 << (size * 8)) - 1);
+
+	return PCIBIOS_SUCCESSFUL;
+}
+
 static struct pci_ops xgene_pcie_ops = {
 	.map_bus = xgene_pcie_map_bus,
-	.read = pci_generic_config_read32,
+	.read = xgene_pcie_config_read32,
 	.write = pci_generic_config_write32,
 };
 
@@ -500,6 +535,10 @@ static int xgene_pcie_probe_bridge(struct platform_device *pdev)
 	port->node = of_node_get(pdev->dev.of_node);
 	port->dev = &pdev->dev;
 
+	port->version = XGENE_PCIE_IP_VER_UNKN;
+	if (of_device_is_compatible(port->node, "apm,xgene-pcie"))
+		port->version = XGENE_PCIE_IP_VER_1;
+
 	ret = xgene_pcie_map_reg(port, pdev);
 	if (ret)
 		return ret;