PCI: sg2042: Add Sophgo SG2042 PCIe driver

Add support for PCIe controller in Sophgo SG2042 SoC. The controller uses
the Cadence PCIe core programmed by pcie-cadence* common driver. The PCIe
controller in SG2042 works in host mode only, supporting data rate up to 16
GT/s and lanes up to x16 or x8.

Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
[mani: reworded description and minor code cleanups]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://patch.msgid.link/01b0a57cd9dba8bed7c1f2d52997046c2c6f042b.1757643388.git.unicorn_wang@outlook.com

drivers/pci/controller/cadence/Kconfig

@@ -42,6 +42,15 @@ config PCIE_CADENCE_PLAT_EP
 	  endpoint mode. This PCIe controller may be embedded into many
 	  different vendors SoCs.
 
+config PCIE_SG2042_HOST
+	tristate "Sophgo SG2042 PCIe controller (host mode)"
+	depends on OF && (ARCH_SOPHGO || COMPILE_TEST)
+	select PCIE_CADENCE_HOST
+	help
+	  Say Y here if you want to support the Sophgo SG2042 PCIe platform
+	  controller in host mode. Sophgo SG2042 PCIe controller uses Cadence
+	  PCIe core.
+
 config PCI_J721E
 	tristate
 	select PCIE_CADENCE_HOST if PCI_J721E_HOST != n
@@ -67,4 +76,5 @@ config PCI_J721E_EP
 	  Say Y here if you want to support the TI J721E PCIe platform
 	  controller in endpoint mode. TI J721E PCIe controller uses Cadence PCIe
 	  core.
+
 endmenu

drivers/pci/controller/cadence/Makefile

@@ -4,3 +4,4 @@ obj-$(CONFIG_PCIE_CADENCE_HOST) += pcie-cadence-host.o
 obj-$(CONFIG_PCIE_CADENCE_EP) += pcie-cadence-ep.o
 obj-$(CONFIG_PCIE_CADENCE_PLAT) += pcie-cadence-plat.o
 obj-$(CONFIG_PCI_J721E) += pci-j721e.o
+obj-$(CONFIG_PCIE_SG2042_HOST) += pcie-sg2042.o

drivers/pci/controller/cadence/pcie-sg2042.c

@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * pcie-sg2042 - PCIe controller driver for Sophgo SG2042 SoC
+ *
+ * Copyright (C) 2025 Sophgo Technology Inc.
+ * Copyright (C) 2025 Chen Wang <unicorn_wang@outlook.com>
+ */
+
+#include <linux/mod_devicetable.h>
+#include <linux/pci.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+
+#include "pcie-cadence.h"
+
+/*
+ * SG2042 only supports 4-byte aligned access, so for the rootbus (i.e. to
+ * read/write the Root Port itself, read32/write32 is required. For
+ * non-rootbus (i.e. to read/write the PCIe peripheral registers, supports
+ * 1/2/4 byte aligned access, so directly using read/write should be fine.
+ */
+
+static struct pci_ops sg2042_pcie_root_ops = {
+	.map_bus	= cdns_pci_map_bus,
+	.read		= pci_generic_config_read32,
+	.write		= pci_generic_config_write32,
+};
+
+static struct pci_ops sg2042_pcie_child_ops = {
+	.map_bus	= cdns_pci_map_bus,
+	.read		= pci_generic_config_read,
+	.write		= pci_generic_config_write,
+};
+
+static int sg2042_pcie_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct pci_host_bridge *bridge;
+	struct cdns_pcie *pcie;
+	struct cdns_pcie_rc *rc;
+	int ret;
+
+	bridge = devm_pci_alloc_host_bridge(dev, sizeof(*rc));
+	if (!bridge)
+		return dev_err_probe(dev, -ENOMEM, "Failed to alloc host bridge!\n");
+
+	bridge->ops = &sg2042_pcie_root_ops;
+	bridge->child_ops = &sg2042_pcie_child_ops;
+
+	rc = pci_host_bridge_priv(bridge);
+	pcie = &rc->pcie;
+	pcie->dev = dev;
+
+	platform_set_drvdata(pdev, pcie);
+
+	pm_runtime_set_active(dev);
+	pm_runtime_no_callbacks(dev);
+	devm_pm_runtime_enable(dev);
+
+	ret = cdns_pcie_init_phy(dev, pcie);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to init phy!\n");
+
+	ret = cdns_pcie_host_setup(rc);
+	if (ret) {
+		dev_err_probe(dev, ret, "Failed to setup host!\n");
+		cdns_pcie_disable_phy(pcie);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void sg2042_pcie_remove(struct platform_device *pdev)
+{
+	struct cdns_pcie *pcie = platform_get_drvdata(pdev);
+	struct device *dev = &pdev->dev;
+	struct cdns_pcie_rc *rc;
+
+	rc = container_of(pcie, struct cdns_pcie_rc, pcie);
+	cdns_pcie_host_disable(rc);
+
+	cdns_pcie_disable_phy(pcie);
+
+	pm_runtime_disable(dev);
+}
+
+static int sg2042_pcie_suspend_noirq(struct device *dev)
+{
+	struct cdns_pcie *pcie = dev_get_drvdata(dev);
+
+	cdns_pcie_disable_phy(pcie);
+
+	return 0;
+}
+
+static int sg2042_pcie_resume_noirq(struct device *dev)
+{
+	struct cdns_pcie *pcie = dev_get_drvdata(dev);
+	int ret;
+
+	ret = cdns_pcie_enable_phy(pcie);
+	if (ret) {
+		dev_err(dev, "failed to enable PHY\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static DEFINE_NOIRQ_DEV_PM_OPS(sg2042_pcie_pm_ops,
+			       sg2042_pcie_suspend_noirq,
+			       sg2042_pcie_resume_noirq);
+
+static const struct of_device_id sg2042_pcie_of_match[] = {
+	{ .compatible = "sophgo,sg2042-pcie-host" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, sg2042_pcie_of_match);
+
+static struct platform_driver sg2042_pcie_driver = {
+	.driver = {
+		.name		= "sg2042-pcie",
+		.of_match_table	= sg2042_pcie_of_match,
+		.pm		= pm_sleep_ptr(&sg2042_pcie_pm_ops),
+	},
+	.probe		= sg2042_pcie_probe,
+	.remove		= sg2042_pcie_remove,
+};
+module_platform_driver(sg2042_pcie_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("PCIe controller driver for SG2042 SoCs");
+MODULE_AUTHOR("Chen Wang <unicorn_wang@outlook.com>");