PCI: mediatek: Add support for EcoNet EN7528 SoC

Add support for the PCIe controller present in the EcoNet EN7528 (and
EN751221) SoCs.

The PCIe controllers present in these SoCs support 2.5 GT/s and 5 GT/s data
rates, but 5 GT/s require re-training after link up.

Co-developed-by: Ahmed Naseef <naseefkm@gmail.com>
Signed-off-by: Ahmed Naseef <naseefkm@gmail.com>
Signed-off-by: Caleb James DeLisle <cjd@cjdns.fr>
[mani: commit log]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/20260702150704.265282-1-cjd@cjdns.fr

drivers/pci/controller/Kconfig

@@ -209,7 +209,7 @@ config PCI_MVEBU
 
 config PCIE_MEDIATEK
 	tristate "MediaTek PCIe controller"
-	depends on ARCH_AIROHA || ARCH_MEDIATEK || COMPILE_TEST
+	depends on ARCH_AIROHA || ARCH_MEDIATEK || ECONET || COMPILE_TEST
 	depends on OF
 	depends on PCI_MSI
 	select IRQ_MSI_LIB

drivers/pci/controller/pcie-mediatek.c

@@ -10,11 +10,13 @@
 #include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/errno.h>
 #include <linux/iopoll.h>
 #include <linux/irq.h>
 #include <linux/irqchip/chained_irq.h>
 #include <linux/irqchip/irq-msi-lib.h>
 #include <linux/irqdomain.h>
+#include <linux/kconfig.h>
 #include <linux/kernel.h>
 #include <linux/mfd/syscon.h>
 #include <linux/msi.h>
@@ -78,6 +80,7 @@
 
 #define PCIE_CONF_VEND_ID	0x100
 #define PCIE_CONF_DEVICE_ID	0x102
+#define PCIE_CONF_REV_CLASS	0x104
 #define PCIE_CONF_CLASS_ID	0x106
 
 #define PCIE_INT_MASK		0x420
@@ -90,6 +93,11 @@
 #define MSI_MASK		BIT(23)
 #define MTK_MSI_IRQS_NUM	32
 
+#define EN7528_HOST_MODE	0x00804201
+#define EN7528_LINKUP_REG	0x50
+#define EN7528_RC0_LINKUP	BIT(1)
+#define EN7528_RC1_LINKUP	BIT(2)
+
 #define PCIE_AHB_TRANS_BASE0_L	0x438
 #define PCIE_AHB_TRANS_BASE0_H	0x43c
 #define AHB2PCIE_SIZE(x)	((x) & GENMASK(4, 0))
@@ -145,12 +153,15 @@ struct mtk_pcie_port;
  * @MTK_PCIE_FIX_DEVICE_ID: host's device ID needed to be fixed
  * @MTK_PCIE_NO_MSI: Bridge has no MSI support, and relies on an external block
  * @MTK_PCIE_SKIP_RSTB: Skip calling RSTB bits on PCIe probe
+ * @MTK_PCIE_RETRAIN: Retrain link to bridge after startup because some
+ *                    Gen2-capable devices start as Gen1.
  */
 enum mtk_pcie_quirks {
 	MTK_PCIE_FIX_CLASS_ID = BIT(0),
 	MTK_PCIE_FIX_DEVICE_ID = BIT(1),
 	MTK_PCIE_NO_MSI = BIT(2),
 	MTK_PCIE_SKIP_RSTB = BIT(3),
+	MTK_PCIE_RETRAIN = BIT(4),
 };
 
 /**
@@ -756,6 +767,134 @@ static int mtk_pcie_startup_port_v2(struct mtk_pcie_port *port)
 	return 0;
 }
 
+static int mtk_pcie_startup_port_en7528(struct mtk_pcie_port *port)
+{
+	struct mtk_pcie *pcie = port->pcie;
+	struct pci_host_bridge *host = pci_host_bridge_from_priv(pcie);
+	struct resource *mem = NULL;
+	struct resource_entry *entry;
+	u32 val, link_mask;
+	int err;
+
+	entry = resource_list_first_type(&host->windows, IORESOURCE_MEM);
+	if (entry)
+		mem = entry->res;
+	if (!mem)
+		return -EINVAL;
+
+	if (!pcie->cfg) {
+		dev_err(pcie->dev, "EN7528: pciecfg syscon not available\n");
+		return -EINVAL;
+	}
+
+	/* Assert all reset signals */
+	writel(0, port->base + PCIE_RST_CTRL);
+
+	/*
+	 * Enable PCIe link down reset, if link status changed from link up to
+	 * link down, this will reset MAC control registers and configuration
+	 * space.
+	 */
+	writel(PCIE_LINKDOWN_RST_EN, port->base + PCIE_RST_CTRL);
+
+	msleep(PCIE_T_PVPERL_MS);
+
+	/* De-assert PHY, PE, PIPE, MAC and configuration reset */
+	val = readl(port->base + PCIE_RST_CTRL);
+	val |= PCIE_PHY_RSTB | PCIE_PERSTB | PCIE_PIPE_SRSTB |
+	       PCIE_MAC_SRSTB | PCIE_CRSTB;
+	writel(val, port->base + PCIE_RST_CTRL);
+
+	writel(PCIE_CLASS_CODE | PCIE_REVISION_ID,
+	       port->base + PCIE_CONF_REV_CLASS);
+	writel(EN7528_HOST_MODE, port->base);
+
+	link_mask = (port->slot == 0) ? EN7528_RC0_LINKUP : EN7528_RC1_LINKUP;
+
+	/* 100ms timeout value should be enough for Gen1/2 training */
+	err = regmap_read_poll_timeout(pcie->cfg, EN7528_LINKUP_REG, val,
+				       !!(val & link_mask), 20,
+				       PCI_PM_D3COLD_WAIT * USEC_PER_MSEC);
+	if (err) {
+		dev_err(pcie->dev, "EN7528: port%d link timeout\n", port->slot);
+		return -ETIMEDOUT;
+	}
+
+	/* Activate INTx interrupts */
+	val = readl(port->base + PCIE_INT_MASK);
+	val &= ~INTX_MASK;
+	writel(val, port->base + PCIE_INT_MASK);
+
+	if (IS_ENABLED(CONFIG_PCI_MSI))
+		mtk_pcie_enable_msi(port);
+
+	/* Set AHB to PCIe translation windows */
+	val = lower_32_bits(mem->start) |
+	      AHB2PCIE_SIZE(fls(resource_size(mem)));
+	writel(val, port->base + PCIE_AHB_TRANS_BASE0_L);
+
+	val = upper_32_bits(mem->start);
+	writel(val, port->base + PCIE_AHB_TRANS_BASE0_H);
+
+	writel(WIN_ENABLE, port->base + PCIE_AXI_WINDOW0);
+
+	if (!IS_BUILTIN(CONFIG_PCIE_MEDIATEK))
+		dev_info(pcie->dev,
+			 "module not built-in, Gen2 unavailable even if supported\n");
+
+	return 0;
+}
+
+/**
+ * mtk_pcie_retrain - retrain the root bridge link if needed
+ * @dev: The device, for use in logging
+ * @host: The host bridge which contains the link
+ *
+ * Due to what is likely a hardware bug, some devices (notably EcoNet) start up
+ * as Gen1, and must be retrained once after initial configuration in order to
+ * reach Gen2.
+ *
+ * These devices always self-identify as Gen2 capable, but sometimes the PHY is
+ * only capable of Gen1 operation, and sometimes the PCIe card (e.g. wifi) is
+ * only Gen1 capable. Therefore it is most convenient to retrain every port
+ * after startup.
+ */
+static int mtk_pcie_retrain(struct device *dev, struct pci_host_bridge *host)
+{
+	struct pci_dev *rp;
+	int ret = -ENOENT;
+	u16 lnksta = 0;
+	u32 speed;
+
+	/* Should already have been warned about during startup_port */
+	if (!IS_BUILTIN(CONFIG_PCIE_MEDIATEK))
+		return 0;
+
+	guard(rwsem_read)(&pci_bus_sem);
+
+	for_each_pci_bridge(rp, host->bus) {
+		if (pci_pcie_type(rp) != PCI_EXP_TYPE_ROOT_PORT)
+			continue;
+
+#if IS_BUILTIN(CONFIG_PCIE_MEDIATEK)
+		ret = pcie_retrain_link(rp, true);
+#endif
+
+		if (ret)
+			return dev_err_probe(&rp->dev, ret,
+					     "failed to retrain port\n");
+
+		pcie_capability_read_word(rp, PCI_EXP_LNKSTA, &lnksta);
+		speed = lnksta & PCI_EXP_LNKSTA_CLS;
+
+		pci_info(rp, "link retrained, speed %s\n",
+			 pci_speed_string(pcie_link_speed[speed]));
+
+	}
+
+	return 0;
+}
+
 static void __iomem *mtk_pcie_map_bus(struct pci_bus *bus,
 				      unsigned int devfn, int where)
 {
@@ -1169,6 +1308,13 @@ static int mtk_pcie_probe(struct platform_device *pdev)
 	if (err)
 		goto put_resources;
 
+	/*
+	 * Ignore error because pci_host_probe() was already called, and in any
+	 * case it is possible that the port will still work as Gen1.
+	 */
+	if (pcie->soc->quirks & MTK_PCIE_RETRAIN)
+		mtk_pcie_retrain(dev, host);
+
 	return 0;
 
 put_resources:
@@ -1290,8 +1436,16 @@ static const struct mtk_pcie_soc mtk_pcie_soc_mt7629 = {
 	.quirks = MTK_PCIE_FIX_CLASS_ID | MTK_PCIE_FIX_DEVICE_ID,
 };
 
+static const struct mtk_pcie_soc mtk_pcie_soc_en7528 = {
+	.ops = &mtk_pcie_ops_v2,
+	.startup = mtk_pcie_startup_port_en7528,
+	.setup_irq = mtk_pcie_setup_irq,
+	.quirks = MTK_PCIE_RETRAIN,
+};
+
 static const struct of_device_id mtk_pcie_ids[] = {
 	{ .compatible = "airoha,an7583-pcie", .data = &mtk_pcie_soc_an7583 },
+	{ .compatible = "econet,en7528-pcie", .data = &mtk_pcie_soc_en7528 },
 	{ .compatible = "mediatek,mt2701-pcie", .data = &mtk_pcie_soc_v1 },
 	{ .compatible = "mediatek,mt7623-pcie", .data = &mtk_pcie_soc_v1 },
 	{ .compatible = "mediatek,mt2712-pcie", .data = &mtk_pcie_soc_mt2712 },