PCI: mvebu: Correctly configure x1/x4 mode

If x1/x4 mode is not set correctly then link with endpoint card is not
established.

Use DTS property 'num-lanes' to deteriminate x1/x4 mode.

Link: https://lore.kernel.org/r/20220222155030.988-6-pali@kernel.org
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

Author: pali

drivers/pci/controller/pci-mvebu.c

@@ -93,6 +93,7 @@ struct mvebu_pcie_port {
 	void __iomem *base;
 	u32 port;
 	u32 lane;
+	bool is_x4;
 	int devfn;
 	unsigned int mem_target;
 	unsigned int mem_attr;
@@ -233,13 +234,25 @@ static void mvebu_pcie_setup_wins(struct mvebu_pcie_port *port)
 
 static void mvebu_pcie_setup_hw(struct mvebu_pcie_port *port)
 {
-	u32 ctrl, cmd, dev_rev, mask;
+	u32 ctrl, lnkcap, cmd, dev_rev, mask;
 
 	/* Setup PCIe controller to Root Complex mode. */
 	ctrl = mvebu_readl(port, PCIE_CTRL_OFF);
 	ctrl |= PCIE_CTRL_RC_MODE;
 	mvebu_writel(port, ctrl, PCIE_CTRL_OFF);
 
+	/*
+	 * Set Maximum Link Width to X1 or X4 in Root Port's PCIe Link
+	 * Capability register. This register is defined by PCIe specification
+	 * as read-only but this mvebu controller has it as read-write and must
+	 * be set to number of SerDes PCIe lanes (1 or 4). If this register is
+	 * not set correctly then link with endpoint card is not established.
+	 */
+	lnkcap = mvebu_readl(port, PCIE_CAP_PCIEXP + PCI_EXP_LNKCAP);
+	lnkcap &= ~PCI_EXP_LNKCAP_MLW;
+	lnkcap |= (port->is_x4 ? 4 : 1) << 4;
+	mvebu_writel(port, lnkcap, PCIE_CAP_PCIEXP + PCI_EXP_LNKCAP);
+
 	/* Disable Root Bridge I/O space, memory space and bus mastering. */
 	cmd = mvebu_readl(port, PCIE_CMD_OFF);
 	cmd &= ~(PCI_COMMAND_IO | PCI_COMMAND_MEMORY | PCI_COMMAND_MASTER);
@@ -982,6 +995,7 @@ static int mvebu_pcie_parse_port(struct mvebu_pcie *pcie,
 	struct device *dev = &pcie->pdev->dev;
 	enum of_gpio_flags flags;
 	int reset_gpio, ret;
+	u32 num_lanes;
 
 	port->pcie = pcie;
 
@@ -994,6 +1008,9 @@ static int mvebu_pcie_parse_port(struct mvebu_pcie *pcie,
 	if (of_property_read_u32(child, "marvell,pcie-lane", &port->lane))
 		port->lane = 0;
 
+	if (!of_property_read_u32(child, "num-lanes", &num_lanes) && num_lanes == 4)
+		port->is_x4 = true;
+
 	port->name = devm_kasprintf(dev, GFP_KERNEL, "pcie%d.%d", port->port,
 				    port->lane);
 	if (!port->name) {