PCI: thunder: Add PCIe host driver for ThunderX processors

The root complexes used to access off-chip PCIe devices (called PEM units
in the hardware manuals) on some Cavium ThunderX processors require quirky
access methods for the config space of the PCIe bridge.

Add a driver to provide these config space accessor functions.  Use the
pci-host-common code to configure the PCI machinery.

Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>

3 files changed, 354 insertions, 0 deletions

diff --git a/drivers/pci/host/Kconfig b/drivers/pci/host/Kconfig
index 65709b4bb3a4..184df22e4a69 100644
--- a/drivers/pci/host/Kconfig
+++ b/drivers/pci/host/Kconfig
@@ -195,4 +195,11 @@ config PCIE_QCOM
 	  PCIe controller uses the Designware core plus Qualcomm-specific
 	  hardware wrappers.
 
+config PCI_HOST_THUNDER_PEM
+	bool "Cavium Thunder PCIe controller to off-chip devices"
+	depends on OF && ARM64
+	select PCI_HOST_COMMON
+	help
+	  Say Y here if you want PCIe support for CN88XX Cavium Thunder SoCs.
+
 endmenu
diff --git a/drivers/pci/host/Makefile b/drivers/pci/host/Makefile
index 3b24af860284..890317234dae 100644
--- a/drivers/pci/host/Makefile
+++ b/drivers/pci/host/Makefile
@@ -23,3 +23,4 @@ obj-$(CONFIG_PCIE_ALTERA) += pcie-altera.o
 obj-$(CONFIG_PCIE_ALTERA_MSI) += pcie-altera-msi.o
 obj-$(CONFIG_PCI_HISI) += pcie-hisi.o
 obj-$(CONFIG_PCIE_QCOM) += pcie-qcom.o
+obj-$(CONFIG_PCI_HOST_THUNDER_PEM) += pci-thunder-pem.o
diff --git a/drivers/pci/host/pci-thunder-pem.c b/drivers/pci/host/pci-thunder-pem.c
new file mode 100644
index 000000000000..cabb92a514ac
--- /dev/null
+++ b/drivers/pci/host/pci-thunder-pem.c
@@ -0,0 +1,346 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright (C) 2015 - 2016 Cavium, Inc.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_pci.h>
+#include <linux/platform_device.h>
+
+#include "pci-host-common.h"
+
+#define PEM_CFG_WR 0x28
+#define PEM_CFG_RD 0x30
+
+struct thunder_pem_pci {
+	struct gen_pci	gen_pci;
+	u32		ea_entry[3];
+	void __iomem	*pem_reg_base;
+};
+
+static void __iomem *thunder_pem_map_bus(struct pci_bus *bus,
+					 unsigned int devfn, int where)
+{
+	struct gen_pci *pci = bus->sysdata;
+	resource_size_t idx = bus->number - pci->cfg.bus_range->start;
+
+	return pci->cfg.win[idx] + ((devfn << 16) | where);
+}
+
+static int thunder_pem_bridge_read(struct pci_bus *bus, unsigned int devfn,
+				   int where, int size, u32 *val)
+{
+	u64 read_val;
+	struct thunder_pem_pci *pem_pci;
+	struct gen_pci *pci = bus->sysdata;
+
+	pem_pci = container_of(pci, struct thunder_pem_pci, gen_pci);
+
+	if (devfn != 0 || where >= 2048) {
+		*val = ~0;
+		return PCIBIOS_DEVICE_NOT_FOUND;
+	}
+
+	/*
+	 * 32-bit accesses only.  Write the address to the low order
+	 * bits of PEM_CFG_RD, then trigger the read by reading back.
+	 * The config data lands in the upper 32-bits of PEM_CFG_RD.
+	 */
+	read_val = where & ~3ull;
+	writeq(read_val, pem_pci->pem_reg_base + PEM_CFG_RD);
+	read_val = readq(pem_pci->pem_reg_base + PEM_CFG_RD);
+	read_val >>= 32;
+
+	/*
+	 * The config space contains some garbage, fix it up.  Also
+	 * synthesize an EA capability for the BAR used by MSI-X.
+	 */
+	switch (where & ~3) {
+	case 0x40:
+		read_val &= 0xffff00ff;
+		read_val |= 0x00007000; /* Skip MSI CAP */
+		break;
+	case 0x70: /* Express Cap */
+		/* PME interrupt on vector 2*/
+		read_val |= (2u << 25);
+		break;
+	case 0xb0: /* MSI-X Cap */
+		/* TableSize=4, Next Cap is EA */
+		read_val &= 0xc00000ff;
+		read_val |= 0x0003bc00;
+		break;
+	case 0xb4:
+		/* Table offset=0, BIR=0 */
+		read_val = 0x00000000;
+		break;
+	case 0xb8:
+		/* BPA offset=0xf0000, BIR=0 */
+		read_val = 0x000f0000;
+		break;
+	case 0xbc:
+		/* EA, 1 entry, no next Cap */
+		read_val = 0x00010014;
+		break;
+	case 0xc0:
+		/* DW2 for type-1 */
+		read_val = 0x00000000;
+		break;
+	case 0xc4:
+		/* Entry BEI=0, PP=0x00, SP=0xff, ES=3 */
+		read_val = 0x80ff0003;
+		break;
+	case 0xc8:
+		read_val = pem_pci->ea_entry[0];
+		break;
+	case 0xcc:
+		read_val = pem_pci->ea_entry[1];
+		break;
+	case 0xd0:
+		read_val = pem_pci->ea_entry[2];
+		break;
+	default:
+		break;
+	}
+	read_val >>= (8 * (where & 3));
+	switch (size) {
+	case 1:
+		read_val &= 0xff;
+		break;
+	case 2:
+		read_val &= 0xffff;
+		break;
+	default:
+		break;
+	}
+	*val = read_val;
+	return PCIBIOS_SUCCESSFUL;
+}
+
+static int thunder_pem_config_read(struct pci_bus *bus, unsigned int devfn,
+				   int where, int size, u32 *val)
+{
+	struct gen_pci *pci = bus->sysdata;
+
+	if (bus->number < pci->cfg.bus_range->start ||
+	    bus->number > pci->cfg.bus_range->end)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+
+	/*
+	 * The first device on the bus is the PEM PCIe bridge.
+	 * Special case its config access.
+	 */
+	if (bus->number == pci->cfg.bus_range->start)
+		return thunder_pem_bridge_read(bus, devfn, where, size, val);
+
+	return pci_generic_config_read(bus, devfn, where, size, val);
+}
+
+/*
+ * Some of the w1c_bits below also include read-only or non-writable
+ * reserved bits, this makes the code simpler and is OK as the bits
+ * are not affected by writing zeros to them.
+ */
+static u32 thunder_pem_bridge_w1c_bits(int where)
+{
+	u32 w1c_bits = 0;
+
+	switch (where & ~3) {
+	case 0x04: /* Command/Status */
+	case 0x1c: /* Base and I/O Limit/Secondary Status */
+		w1c_bits = 0xff000000;
+		break;
+	case 0x44: /* Power Management Control and Status */
+		w1c_bits = 0xfffffe00;
+		break;
+	case 0x78: /* Device Control/Device Status */
+	case 0x80: /* Link Control/Link Status */
+	case 0x88: /* Slot Control/Slot Status */
+	case 0x90: /* Root Status */
+	case 0xa0: /* Link Control 2 Registers/Link Status 2 */
+		w1c_bits = 0xffff0000;
+		break;
+	case 0x104: /* Uncorrectable Error Status */
+	case 0x110: /* Correctable Error Status */
+	case 0x130: /* Error Status */
+	case 0x160: /* Link Control 4 */
+		w1c_bits = 0xffffffff;
+		break;
+	default:
+		break;
+	}
+	return w1c_bits;
+}
+
+static int thunder_pem_bridge_write(struct pci_bus *bus, unsigned int devfn,
+				    int where, int size, u32 val)
+{
+	struct gen_pci *pci = bus->sysdata;
+	struct thunder_pem_pci *pem_pci;
+	u64 write_val, read_val;
+	u32 mask = 0;
+
+	pem_pci = container_of(pci, struct thunder_pem_pci, gen_pci);
+
+	if (devfn != 0 || where >= 2048)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+
+	/*
+	 * 32-bit accesses only.  If the write is for a size smaller
+	 * than 32-bits, we must first read the 32-bit value and merge
+	 * in the desired bits and then write the whole 32-bits back
+	 * out.
+	 */
+	switch (size) {
+	case 1:
+		read_val = where & ~3ull;
+		writeq(read_val, pem_pci->pem_reg_base + PEM_CFG_RD);
+		read_val = readq(pem_pci->pem_reg_base + PEM_CFG_RD);
+		read_val >>= 32;
+		mask = ~(0xff << (8 * (where & 3)));
+		read_val &= mask;
+		val = (val & 0xff) << (8 * (where & 3));
+		val |= (u32)read_val;
+		break;
+	case 2:
+		read_val = where & ~3ull;
+		writeq(read_val, pem_pci->pem_reg_base + PEM_CFG_RD);
+		read_val = readq(pem_pci->pem_reg_base + PEM_CFG_RD);
+		read_val >>= 32;
+		mask = ~(0xffff << (8 * (where & 3)));
+		read_val &= mask;
+		val = (val & 0xffff) << (8 * (where & 3));
+		val |= (u32)read_val;
+		break;
+	default:
+		break;
+	}
+
+	/*
+	 * By expanding the write width to 32 bits, we may
+	 * inadvertently hit some W1C bits that were not intended to
+	 * be written.  Calculate the mask that must be applied to the
+	 * data to be written to avoid these cases.
+	 */
+	if (mask) {
+		u32 w1c_bits = thunder_pem_bridge_w1c_bits(where);
+
+		if (w1c_bits) {
+			mask &= w1c_bits;
+			val &= ~mask;
+		}
+	}
+
+	/*
+	 * Low order bits are the config address, the high order 32
+	 * bits are the data to be written.
+	 */
+	write_val = where & ~3ull;
+	write_val |= (((u64)val) << 32);
+	writeq(write_val, pem_pci->pem_reg_base + PEM_CFG_WR);
+	return PCIBIOS_SUCCESSFUL;
+}
+
+static int thunder_pem_config_write(struct pci_bus *bus, unsigned int devfn,
+				    int where, int size, u32 val)
+{
+	struct gen_pci *pci = bus->sysdata;
+
+	if (bus->number < pci->cfg.bus_range->start ||
+	    bus->number > pci->cfg.bus_range->end)
+		return PCIBIOS_DEVICE_NOT_FOUND;
+	/*
+	 * The first device on the bus is the PEM PCIe bridge.
+	 * Special case its config access.
+	 */
+	if (bus->number == pci->cfg.bus_range->start)
+		return thunder_pem_bridge_write(bus, devfn, where, size, val);
+
+
+	return pci_generic_config_write(bus, devfn, where, size, val);
+}
+
+static struct gen_pci_cfg_bus_ops thunder_pem_bus_ops = {
+	.bus_shift	= 24,
+	.ops		= {
+		.map_bus	= thunder_pem_map_bus,
+		.read		= thunder_pem_config_read,
+		.write		= thunder_pem_config_write,
+	}
+};
+
+static const struct of_device_id thunder_pem_of_match[] = {
+	{ .compatible = "cavium,pci-host-thunder-pem",
+	  .data = &thunder_pem_bus_ops },
+
+	{ },
+};
+MODULE_DEVICE_TABLE(of, thunder_pem_of_match);
+
+static int thunder_pem_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	const struct of_device_id *of_id;
+	resource_size_t bar4_start;
+	struct resource *res_pem;
+	struct thunder_pem_pci *pem_pci;
+
+	pem_pci = devm_kzalloc(dev, sizeof(*pem_pci), GFP_KERNEL);
+	if (!pem_pci)
+		return -ENOMEM;
+
+	of_id = of_match_node(thunder_pem_of_match, dev->of_node);
+	pem_pci->gen_pci.cfg.ops = (struct gen_pci_cfg_bus_ops *)of_id->data;
+
+	/*
+	 * The second register range is the PEM bridge to the PCIe
+	 * bus.  It has a different config access method than those
+	 * devices behind the bridge.
+	 */
+	res_pem = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+	if (!res_pem) {
+		dev_err(dev, "missing \"reg[1]\"property\n");
+		return -EINVAL;
+	}
+
+	pem_pci->pem_reg_base = devm_ioremap(dev, res_pem->start, 0x10000);
+	if (!pem_pci->pem_reg_base)
+		return -ENOMEM;
+
+	/*
+	 * The MSI-X BAR for the PEM and AER interrupts is located at
+	 * a fixed offset from the PEM register base.  Generate a
+	 * fragment of the synthesized Enhanced Allocation capability
+	 * structure here for the BAR.
+	 */
+	bar4_start = res_pem->start + 0xf00000;
+	pem_pci->ea_entry[0] = (u32)bar4_start | 2;
+	pem_pci->ea_entry[1] = (u32)(res_pem->end - bar4_start) & ~3u;
+	pem_pci->ea_entry[2] = (u32)(bar4_start >> 32);
+
+	return pci_host_common_probe(pdev, &pem_pci->gen_pci);
+}
+
+static struct platform_driver thunder_pem_driver = {
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.of_match_table = thunder_pem_of_match,
+	},
+	.probe = thunder_pem_probe,
+};
+module_platform_driver(thunder_pem_driver);
+
+MODULE_DESCRIPTION("Thunder PEM PCIe host driver");
+MODULE_LICENSE("GPL v2");