PCI: brcmstb: Set MLW based on "num-lanes" DT property if present

By default, the driver relies on the default hardware defined value for the
Max Link Width (MLW) capability. But if the "num-lanes" DT property is
present, assume that the chip's default capability information is incorrect
or undesired, and use the specified value instead.

Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
[mani: reworded the description and comments]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20250530224035.41886-3-james.quinlan@broadcom.com

Author: jamesequinlan

drivers/pci/controller/pcie-brcmstb.c

@@ -46,6 +46,7 @@
 #define  PCIE_RC_CFG_PRIV1_ID_VAL3_CLASS_CODE_MASK	0xffffff
 
 #define PCIE_RC_CFG_PRIV1_LINK_CAPABILITY			0x04dc
+#define  PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_MAX_LINK_WIDTH_MASK	0x1f0
 #define  PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_ASPM_SUPPORT_MASK	0xc00
 
 #define PCIE_RC_CFG_PRIV1_ROOT_CAP			0x4f8
@@ -55,6 +56,9 @@
 #define PCIE_RC_DL_MDIO_WR_DATA				0x1104
 #define PCIE_RC_DL_MDIO_RD_DATA				0x1108
 
+#define PCIE_RC_PL_REG_PHY_CTL_1			0x1804
+#define  PCIE_RC_PL_REG_PHY_CTL_1_REG_P2_POWERDOWN_ENA_NOSYNC_MASK	0x8
+
 #define PCIE_RC_PL_PHY_CTL_15				0x184c
 #define  PCIE_RC_PL_PHY_CTL_15_DIS_PLL_PD_MASK		0x400000
 #define  PCIE_RC_PL_PHY_CTL_15_PM_CLK_PERIOD_MASK	0xff
@@ -1072,7 +1076,7 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
 	void __iomem *base = pcie->base;
 	struct pci_host_bridge *bridge;
 	struct resource_entry *entry;
-	u32 tmp, burst, aspm_support;
+	u32 tmp, burst, aspm_support, num_lanes, num_lanes_cap;
 	u8 num_out_wins = 0;
 	int num_inbound_wins = 0;
 	int memc, ret;
@@ -1180,6 +1184,27 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
 		PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_ASPM_SUPPORT_MASK);
 	writel(tmp, base + PCIE_RC_CFG_PRIV1_LINK_CAPABILITY);
 
+	/* 'tmp' still holds the contents of PRIV1_LINK_CAPABILITY */
+	num_lanes_cap = u32_get_bits(tmp, PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_MAX_LINK_WIDTH_MASK);
+	num_lanes = 0;
+
+	/*
+	 * Use hardware negotiated Max Link Width value by default.  If the
+	 * "num-lanes" DT property is present, assume that the chip's default
+	 * link width capability information is incorrect/undesired and use the
+	 * specified value instead.
+	 */
+	if (!of_property_read_u32(pcie->np, "num-lanes", &num_lanes) &&
+	    num_lanes && num_lanes <= 4 && num_lanes_cap != num_lanes) {
+		u32p_replace_bits(&tmp, num_lanes,
+			PCIE_RC_CFG_PRIV1_LINK_CAPABILITY_MAX_LINK_WIDTH_MASK);
+		writel(tmp, base + PCIE_RC_CFG_PRIV1_LINK_CAPABILITY);
+		tmp = readl(base + PCIE_RC_PL_REG_PHY_CTL_1);
+		u32p_replace_bits(&tmp, 1,
+			PCIE_RC_PL_REG_PHY_CTL_1_REG_P2_POWERDOWN_ENA_NOSYNC_MASK);
+		writel(tmp, base + PCIE_RC_PL_REG_PHY_CTL_1);
+	}
+
 	/*
 	 * For config space accesses on the RC, show the right class for
 	 * a PCIe-PCIe bridge (the default setting is to be EP mode).