PCI: Add Loongson PCI Controller support

This controller can be found on Loongson-2K SoC, Loongson-3
systems with RS780E/LS7A PCH.

The RS780E part of code was previously located at
arch/mips/pci/ops-loongson3.c and now it can use generic PCI
driver implementation.

Signed-off-by: Jiaxun Yang <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Acked-by: Lorenzo Pieralisi <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

drivers/pci/controller/Kconfig

···
 	  The Hyper-V PCI Interface is a helper driver allows other drivers to
 	  have a common interface with the Hyper-V PCI frontend driver.
 
+config PCI_LOONGSON
+	bool "LOONGSON PCI Controller"
+	depends on MACH_LOONGSON64 || COMPILE_TEST
+	depends on OF
+	depends on PCI_QUIRKS
+	default MACH_LOONGSON64
+	help
+	  Say Y here if you want to enable PCI controller support on
+	  Loongson systems.
+
 source "drivers/pci/controller/dwc/Kconfig"
 source "drivers/pci/controller/mobiveil/Kconfig"
 source "drivers/pci/controller/cadence/Kconfig"

drivers/pci/controller/Makefile

···
 obj-$(CONFIG_PCIE_TANGO_SMP8759) += pcie-tango.o
 obj-$(CONFIG_VMD) += vmd.o
 obj-$(CONFIG_PCIE_BRCMSTB) += pcie-brcmstb.o
+obj-$(CONFIG_PCI_LOONGSON) += pci-loongson.o
 # pcie-hisi.o quirks are needed even without CONFIG_PCIE_DW
 obj-y				+= dwc/
 obj-y				+= mobiveil/

drivers/pci/controller/pci-loongson.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Loongson PCI Host Controller Driver
+ *
+ * Copyright (C) 2020 Jiaxun Yang <[e-mail]>
+ */
+
+#include <linux/of_device.h>
+#include <linux/of_pci.h>
+#include <linux/pci.h>
+#include <linux/pci_ids.h>
+
+#include "../pci.h"
+
+/* Device IDs */
+#define DEV_PCIE_PORT_0	0x7a09
+#define DEV_PCIE_PORT_1	0x7a19
+#define DEV_PCIE_PORT_2	0x7a29
+
+#define DEV_LS2K_APB	0x7a02
+#define DEV_LS7A_CONF	0x7a10
+#define DEV_LS7A_LPC	0x7a0c
+
+#define FLAG_CFG0	BIT(0)
+#define FLAG_CFG1	BIT(1)
+#define FLAG_DEV_FIX	BIT(2)
+
+struct loongson_pci {
+	void __iomem *cfg0_base;
+	void __iomem *cfg1_base;
+	struct platform_device *pdev;
+	u32 flags;
+};
+
+/* Fixup wrong class code in PCIe bridges */
+static void bridge_class_quirk(struct pci_dev *dev)
+{
+	dev->class = PCI_CLASS_BRIDGE_PCI << 8;
+}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_0, bridge_class_quirk);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_1, bridge_class_quirk);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_2, bridge_class_quirk);
+
+static void system_bus_quirk(struct pci_dev *pdev)
+{
+	/*
+	 * The address space consumed by these devices is outside the
+	 * resources of the host bridge.
+	 */
+	pdev->mmio_always_on = 1;
+	pdev->non_compliant_bars = 1;
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_LS2K_APB, system_bus_quirk);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_LS7A_CONF, system_bus_quirk);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_LS7A_LPC, system_bus_quirk);
+
+static void loongson_mrrs_quirk(struct pci_dev *dev)
+{
+	struct pci_bus *bus = dev->bus;
+	struct pci_dev *bridge;
+	static const struct pci_device_id bridge_devids[] = {
+		{ PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_0) },
+		{ PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_1) },
+		{ PCI_VDEVICE(LOONGSON, DEV_PCIE_PORT_2) },
+		{ 0, },
+	};
+
+	/* look for the matching bridge */
+	while (!pci_is_root_bus(bus)) {
+		bridge = bus->self;
+		bus = bus->parent;
+		/*
+		 * Some Loongson PCIe ports have a h/w limitation of
+		 * 256 bytes maximum read request size. They can't handle
+		 * anything larger than this. So force this limit on
+		 * any devices attached under these ports.
+		 */
+		if (pci_match_id(bridge_devids, bridge)) {
+			if (pcie_get_readrq(dev) > 256) {
+				pci_info(dev, "limiting MRRS to 256\n");
+				pcie_set_readrq(dev, 256);
+			}
+			break;
+		}
+	}
+}
+DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID, loongson_mrrs_quirk);
+
+static void __iomem *cfg1_map(struct loongson_pci *priv, int bus,
+				unsigned int devfn, int where)
+{
+	unsigned long addroff = 0x0;
+
+	if (bus != 0)
+		addroff |= BIT(28); /* Type 1 Access */
+	addroff |= (where & 0xff) | ((where & 0xf00) << 16);
+	addroff |= (bus << 16) | (devfn << 8);
+	return priv->cfg1_base + addroff;
+}
+
+static void __iomem *cfg0_map(struct loongson_pci *priv, int bus,
+				unsigned int devfn, int where)
+{
+	unsigned long addroff = 0x0;
+
+	if (bus != 0)
+		addroff |= BIT(24); /* Type 1 Access */
+	addroff |= (bus << 16) | (devfn << 8) | where;
+	return priv->cfg0_base + addroff;
+}
+
+static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devfn,
+			       int where)
+{
+	unsigned char busnum = bus->number;
+	struct pci_host_bridge *bridge = pci_find_host_bridge(bus);
+	struct loongson_pci *priv =  pci_host_bridge_priv(bridge);
+
+	/*
+	 * Do not read more than one device on the bus other than
+	 * the host bus. For our hardware the root bus is always bus 0.
+	 */
+	if (priv->flags & FLAG_DEV_FIX && busnum != 0 &&
+		PCI_SLOT(devfn) > 0)
+		return NULL;
+
+	/* CFG0 can only access standard space */
+	if (where < PCI_CFG_SPACE_SIZE && priv->cfg0_base)
+		return cfg0_map(priv, busnum, devfn, where);
+
+	/* CFG1 can access extended space */
+	if (where < PCI_CFG_SPACE_EXP_SIZE && priv->cfg1_base)
+		return cfg1_map(priv, busnum, devfn, where);
+
+	return NULL;
+}
+
+static int loongson_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
+{
+	int irq;
+	u8 val;
+
+	irq = of_irq_parse_and_map_pci(dev, slot, pin);
+	if (irq > 0)
+		return irq;
+
+	/* Care i8259 legacy systems */
+	pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &val);
+	/* i8259 only have 15 IRQs */
+	if (val > 15)
+		return 0;
+
+	return val;
+}
+
+/* H/w only accept 32-bit PCI operations */
+static struct pci_ops loongson_pci_ops = {
+	.map_bus = pci_loongson_map_bus,
+	.read	= pci_generic_config_read32,
+	.write	= pci_generic_config_write32,
+};
+
+static const struct of_device_id loongson_pci_of_match[] = {
+	{ .compatible = "loongson,ls2k-pci",
+		.data = (void *)(FLAG_CFG0 | FLAG_CFG1 | FLAG_DEV_FIX), },
+	{ .compatible = "loongson,ls7a-pci",
+		.data = (void *)(FLAG_CFG0 | FLAG_CFG1 | FLAG_DEV_FIX), },
+	{ .compatible = "loongson,rs780e-pci",
+		.data = (void *)(FLAG_CFG0), },
+	{}
+};
+
+static int loongson_pci_probe(struct platform_device *pdev)
+{
+	struct loongson_pci *priv;
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+	struct pci_host_bridge *bridge;
+	struct resource *regs;
+	int err;
+
+	if (!node)
+		return -ENODEV;
+
+	bridge = devm_pci_alloc_host_bridge(dev, sizeof(*priv));
+	if (!bridge)
+		return -ENODEV;
+
+	priv = pci_host_bridge_priv(bridge);
+	priv->pdev = pdev;
+	priv->flags = (unsigned long)of_device_get_match_data(dev);
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!regs) {
+		dev_err(dev, "missing mem resources for cfg0\n");
+		return -EINVAL;
+	}
+
+	priv->cfg0_base = devm_pci_remap_cfg_resource(dev, regs);
+	if (IS_ERR(priv->cfg0_base))
+		return PTR_ERR(priv->cfg0_base);
+
+	/* CFG1 is optional */
+	if (priv->flags & FLAG_CFG1) {
+		regs = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+		if (!regs)
+			dev_info(dev, "missing mem resource for cfg1\n");
+		else {
+			priv->cfg1_base = devm_pci_remap_cfg_resource(dev, regs);
+			if (IS_ERR(priv->cfg1_base))
+				priv->cfg1_base = NULL;
+		}
+	}
+
+	err = pci_parse_request_of_pci_ranges(dev, &bridge->windows,
+						&bridge->dma_ranges, NULL);
+	if (err) {
+		dev_err(dev, "failed to get bridge resources\n");
+		return err;
+	}
+
+	bridge->dev.parent = dev;
+	bridge->sysdata = priv;
+	bridge->ops = &loongson_pci_ops;
+	bridge->map_irq = loongson_map_irq;
+
+	err = pci_host_probe(bridge);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static struct platform_driver loongson_pci_driver = {
+	.driver = {
+		.name = "loongson-pci",
+		.of_match_table = loongson_pci_of_match,
+	},
+	.probe = loongson_pci_probe,
+};
+builtin_platform_driver(loongson_pci_driver);