PCI: Introduce PCI bridge emulated config space common logic

Some PCI host controllers do not expose a configuration space for the
root port PCI bridge. Due to this, the Marvell Armada 370/38x/XP PCI
controller driver (pci-mvebu) emulates a root port PCI bridge
configuration space, and uses that to (among other things) dynamically
create the memory windows that correspond to the PCI MEM and I/O
regions.

Since we now need to add a very similar logic for the Marvell Armada
37xx PCI controller driver (pci-aardvark), instead of duplicating the
code, we create in this commit a common logic called pci-bridge-emul.

The idea of this logic is to emulate a root port PCI bridge
configuration space by providing configuration space read/write
operations, and faking behind the scenes the configuration space of a
PCI bridge. A PCI host controller driver simply has to call
pci_bridge_emul_conf_read() and pci_bridge_emul_conf_write() to
read/write the configuration space of the bridge.

By default, the PCI bridge configuration space is simply emulated by a
chunk of memory, but the PCI host controller can override the behavior
of the read and write operations on a per-register basis to do
additional actions if needed. We take care of complying with the
behavior of the PCI configuration space registers in terms of bits
that are read-write, read-only, reserved and write-1-to-clear.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Russell King <rmk+kernel@armlinux.org.uk>

4 files changed, 536 insertions, 0 deletions

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 56ff8f6d31fc..4a28e07d4c0e 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -98,6 +98,9 @@ config PCI_ECAM
 config PCI_LOCKLESS_CONFIG
 	bool
 
+config PCI_BRIDGE_EMUL
+	bool
+
 config PCI_IOV
 	bool "PCI IOV support"
 	depends on PCI
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index 1b2cfe51e8d7..3e5caf7347e9 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_HOTPLUG_PCI)	+= hotplug/
 obj-$(CONFIG_PCI_MSI)		+= msi.o
 obj-$(CONFIG_PCI_ATS)		+= ats.o
 obj-$(CONFIG_PCI_IOV)		+= iov.o
+obj-$(CONFIG_PCI_BRIDGE_EMUL)	+= pci-bridge-emul.o
 obj-$(CONFIG_ACPI)		+= pci-acpi.o
 obj-$(CONFIG_PCI_LABEL)		+= pci-label.o
 obj-$(CONFIG_X86_INTEL_MID)	+= pci-mid.o
diff --git a/drivers/pci/pci-bridge-emul.c b/drivers/pci/pci-bridge-emul.c
new file mode 100644
index 000000000000..129738362d90
--- /dev/null
+++ b/drivers/pci/pci-bridge-emul.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018 Marvell
+ *
+ * Author: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
+ *
+ * This file helps PCI controller drivers implement a fake root port
+ * PCI bridge when the HW doesn't provide such a root port PCI
+ * bridge.
+ *
+ * It emulates a PCI bridge by providing a fake PCI configuration
+ * space (and optionally a PCIe capability configuration space) in
+ * memory. By default the read/write operations simply read and update
+ * this fake configuration space in memory. However, PCI controller
+ * drivers can provide through the 'struct pci_sw_bridge_ops'
+ * structure a set of operations to override or complement this
+ * default behavior.
+ */
+
+#include <linux/pci.h>
+#include "pci-bridge-emul.h"
+
+#define PCI_BRIDGE_CONF_END	PCI_STD_HEADER_SIZEOF
+#define PCI_CAP_PCIE_START	PCI_BRIDGE_CONF_END
+#define PCI_CAP_PCIE_END	(PCI_CAP_PCIE_START + PCI_EXP_SLTSTA2 + 2)
+
+/*
+ * Initialize a pci_bridge_emul structure to represent a fake PCI
+ * bridge configuration space. The caller needs to have initialized
+ * the PCI configuration space with whatever values make sense
+ * (typically at least vendor, device, revision), the ->ops pointer,
+ * and optionally ->data and ->has_pcie.
+ */
+void pci_bridge_emul_init(struct pci_bridge_emul *bridge)
+{
+	bridge->conf.class_revision |= PCI_CLASS_BRIDGE_PCI << 16;
+	bridge->conf.header_type = PCI_HEADER_TYPE_BRIDGE;
+	bridge->conf.cache_line_size = 0x10;
+	bridge->conf.status = PCI_STATUS_CAP_LIST;
+
+	if (bridge->has_pcie) {
+		bridge->conf.capabilities_pointer = PCI_CAP_PCIE_START;
+		bridge->pcie_conf.cap_id = PCI_CAP_ID_EXP;
+		/* Set PCIe v2, root port, slot support */
+		bridge->pcie_conf.cap = PCI_EXP_TYPE_ROOT_PORT << 4 | 2 |
+			PCI_EXP_FLAGS_SLOT;
+	}
+}
+
+struct pci_bridge_reg_behavior {
+	/* Read-only bits */
+	u32 ro;
+
+	/* Read-write bits */
+	u32 rw;
+
+	/* Write-1-to-clear bits */
+	u32 w1c;
+
+	/* Reserved bits (hardwired to 0) */
+	u32 rsvd;
+};
+
+const static struct pci_bridge_reg_behavior pci_regs_behavior[] = {
+	[PCI_VENDOR_ID / 4] = { .ro = ~0 },
+	[PCI_COMMAND / 4] = {
+		.rw = (PCI_COMMAND_IO | PCI_COMMAND_MEMORY |
+		       PCI_COMMAND_MASTER | PCI_COMMAND_PARITY |
+		       PCI_COMMAND_SERR),
+		.ro = ((PCI_COMMAND_SPECIAL | PCI_COMMAND_INVALIDATE |
+			PCI_COMMAND_VGA_PALETTE | PCI_COMMAND_WAIT |
+			PCI_COMMAND_FAST_BACK) |
+		       (PCI_STATUS_CAP_LIST | PCI_STATUS_66MHZ |
+			PCI_STATUS_FAST_BACK | PCI_STATUS_DEVSEL_MASK) << 16),
+		.rsvd = GENMASK(15, 10) | ((BIT(6) | GENMASK(3, 0)) << 16),
+		.w1c = (PCI_STATUS_PARITY |
+			PCI_STATUS_SIG_TARGET_ABORT |
+			PCI_STATUS_REC_TARGET_ABORT |
+			PCI_STATUS_REC_MASTER_ABORT |
+			PCI_STATUS_SIG_SYSTEM_ERROR |
+			PCI_STATUS_DETECTED_PARITY) << 16,
+	},
+	[PCI_CLASS_REVISION / 4] = { .ro = ~0 },
+
+	/*
+	 * Cache Line Size register: implement as read-only, we do not
+	 * pretend implementing "Memory Write and Invalidate"
+	 * transactions"
+	 *
+	 * Latency Timer Register: implemented as read-only, as "A
+	 * bridge that is not capable of a burst transfer of more than
+	 * two data phases on its primary interface is permitted to
+	 * hardwire the Latency Timer to a value of 16 or less"
+	 *
+	 * Header Type: always read-only
+	 *
+	 * BIST register: implemented as read-only, as "A bridge that
+	 * does not support BIST must implement this register as a
+	 * read-only register that returns 0 when read"
+	 */
+	[PCI_CACHE_LINE_SIZE / 4] = { .ro = ~0 },
+
+	/*
+	 * Base Address registers not used must be implemented as
+	 * read-only registers that return 0 when read.
+	 */
+	[PCI_BASE_ADDRESS_0 / 4] = { .ro = ~0 },
+	[PCI_BASE_ADDRESS_1 / 4] = { .ro = ~0 },
+
+	[PCI_PRIMARY_BUS / 4] = {
+		/* Primary, secondary and subordinate bus are RW */
+		.rw = GENMASK(24, 0),
+		/* Secondary latency is read-only */
+		.ro = GENMASK(31, 24),
+	},
+
+	[PCI_IO_BASE / 4] = {
+		/* The high four bits of I/O base/limit are RW */
+		.rw = (GENMASK(15, 12) | GENMASK(7, 4)),
+
+		/* The low four bits of I/O base/limit are RO */
+		.ro = (((PCI_STATUS_66MHZ | PCI_STATUS_FAST_BACK |
+			 PCI_STATUS_DEVSEL_MASK) << 16) |
+		       GENMASK(11, 8) | GENMASK(3, 0)),
+
+		.w1c = (PCI_STATUS_PARITY |
+			PCI_STATUS_SIG_TARGET_ABORT |
+			PCI_STATUS_REC_TARGET_ABORT |
+			PCI_STATUS_REC_MASTER_ABORT |
+			PCI_STATUS_SIG_SYSTEM_ERROR |
+			PCI_STATUS_DETECTED_PARITY) << 16,
+
+		.rsvd = ((BIT(6) | GENMASK(4, 0)) << 16),
+	},
+
+	[PCI_MEMORY_BASE / 4] = {
+		/* The high 12-bits of mem base/limit are RW */
+		.rw = GENMASK(31, 20) | GENMASK(15, 4),
+
+		/* The low four bits of mem base/limit are RO */
+		.ro = GENMASK(19, 16) | GENMASK(3, 0),
+	},
+
+	[PCI_PREF_MEMORY_BASE / 4] = {
+		/* The high 12-bits of pref mem base/limit are RW */
+		.rw = GENMASK(31, 20) | GENMASK(15, 4),
+
+		/* The low four bits of pref mem base/limit are RO */
+		.ro = GENMASK(19, 16) | GENMASK(3, 0),
+	},
+
+	[PCI_PREF_BASE_UPPER32 / 4] = {
+		.rw = ~0,
+	},
+
+	[PCI_PREF_LIMIT_UPPER32 / 4] = {
+		.rw = ~0,
+	},
+
+	[PCI_IO_BASE_UPPER16 / 4] = {
+		.rw = ~0,
+	},
+
+	[PCI_CAPABILITY_LIST / 4] = {
+		.ro = GENMASK(7, 0),
+		.rsvd = GENMASK(31, 8),
+	},
+
+	[PCI_ROM_ADDRESS1 / 4] = {
+		.rw = GENMASK(31, 11) | BIT(0),
+		.rsvd = GENMASK(10, 1),
+	},
+
+	/*
+	 * Interrupt line (bits 7:0) are RW, interrupt pin (bits 15:8)
+	 * are RO, and bridge control (31:16) are a mix of RW, RO,
+	 * reserved and W1C bits
+	 */
+	[PCI_INTERRUPT_LINE / 4] = {
+		/* Interrupt line is RW */
+		.rw = (GENMASK(7, 0) |
+		       ((PCI_BRIDGE_CTL_PARITY |
+			 PCI_BRIDGE_CTL_SERR |
+			 PCI_BRIDGE_CTL_ISA |
+			 PCI_BRIDGE_CTL_VGA |
+			 PCI_BRIDGE_CTL_MASTER_ABORT |
+			 PCI_BRIDGE_CTL_BUS_RESET |
+			 BIT(8) | BIT(9) | BIT(11)) << 16)),
+
+		/* Interrupt pin is RO */
+		.ro = (GENMASK(15, 8) | ((PCI_BRIDGE_CTL_FAST_BACK) << 16)),
+
+		.w1c = BIT(10) << 16,
+
+		.rsvd = (GENMASK(15, 12) | BIT(4)) << 16,
+	},
+};
+
+const static struct pci_bridge_reg_behavior pcie_cap_regs_behavior[] = {
+	[PCI_CAP_LIST_ID / 4] = {
+		/*
+		 * Capability ID, Next Capability Pointer and
+		 * Capabilities register are all read-only.
+		 */
+		.ro = ~0,
+	},
+
+	[PCI_EXP_DEVCAP / 4] = {
+		.ro = ~0,
+	},
+
+	[PCI_EXP_DEVCTL / 4] = {
+		/* Device control register is RW */
+		.rw = GENMASK(15, 0),
+
+		/*
+		 * Device status register has 4 bits W1C, then 2 bits
+		 * RO, the rest is reserved
+		 */
+		.w1c = GENMASK(19, 16),
+		.ro = GENMASK(20, 19),
+		.rsvd = GENMASK(31, 21),
+	},
+
+	[PCI_EXP_LNKCAP / 4] = {
+		/* All bits are RO, except bit 23 which is reserved */
+		.ro = lower_32_bits(~BIT(23)),
+		.rsvd = BIT(23),
+	},
+
+	[PCI_EXP_LNKCTL / 4] = {
+		/*
+		 * Link control has bits [1:0] and [11:3] RW, the
+		 * other bits are reserved.
+		 * Link status has bits [13:0] RO, and bits [14:15]
+		 * W1C.
+		 */
+		.rw = GENMASK(11, 3) | GENMASK(1, 0),
+		.ro = GENMASK(13, 0) << 16,
+		.w1c = GENMASK(15, 14) << 16,
+		.rsvd = GENMASK(15, 12) | BIT(2),
+	},
+
+	[PCI_EXP_SLTCAP / 4] = {
+		.ro = ~0,
+	},
+
+	[PCI_EXP_SLTCTL / 4] = {
+		/*
+		 * Slot control has bits [12:0] RW, the rest is
+		 * reserved.
+		 *
+		 * Slot status has a mix of W1C and RO bits, as well
+		 * as reserved bits.
+		 */
+		.rw = GENMASK(12, 0),
+		.w1c = (PCI_EXP_SLTSTA_ABP | PCI_EXP_SLTSTA_PFD |
+			PCI_EXP_SLTSTA_MRLSC | PCI_EXP_SLTSTA_PDC |
+			PCI_EXP_SLTSTA_CC | PCI_EXP_SLTSTA_DLLSC) << 16,
+		.ro = (PCI_EXP_SLTSTA_MRLSS | PCI_EXP_SLTSTA_PDS |
+		       PCI_EXP_SLTSTA_EIS) << 16,
+		.rsvd = GENMASK(15, 12) | (GENMASK(15, 9) << 16),
+	},
+
+	[PCI_EXP_RTCTL / 4] = {
+		/*
+		 * Root control has bits [4:0] RW, the rest is
+		 * reserved.
+		 *
+		 * Root status has bit 0 RO, the rest is reserved.
+		 */
+		.rw = (PCI_EXP_RTCTL_SECEE | PCI_EXP_RTCTL_SENFEE |
+		       PCI_EXP_RTCTL_SEFEE | PCI_EXP_RTCTL_PMEIE |
+		       PCI_EXP_RTCTL_CRSSVE),
+		.ro = PCI_EXP_RTCAP_CRSVIS << 16,
+		.rsvd = GENMASK(15, 5) | (GENMASK(15, 1) << 16),
+	},
+
+	[PCI_EXP_RTSTA / 4] = {
+		.ro = GENMASK(15, 0) | PCI_EXP_RTSTA_PENDING,
+		.w1c = PCI_EXP_RTSTA_PME,
+		.rsvd = GENMASK(31, 18),
+	},
+};
+
+/*
+ * Should be called by the PCI controller driver when reading the PCI
+ * configuration space of the fake bridge. It will call back the
+ * ->ops->read_base or ->ops->read_pcie operations.
+ */
+int pci_bridge_emul_conf_read(struct pci_bridge_emul *bridge, int where,
+			      int size, u32 *value)
+{
+	int ret;
+	int reg = where & ~3;
+	pci_bridge_emul_read_status_t (*read_op)(struct pci_bridge_emul *bridge,
+						 int reg, u32 *value);
+	u32 *cfgspace;
+	const struct pci_bridge_reg_behavior *behavior;
+
+	if (bridge->has_pcie && reg >= PCI_CAP_PCIE_END) {
+		*value = 0;
+		return PCIBIOS_SUCCESSFUL;
+	}
+
+	if (!bridge->has_pcie && reg >= PCI_BRIDGE_CONF_END) {
+		*value = 0;
+		return PCIBIOS_SUCCESSFUL;
+	}
+
+	if (bridge->has_pcie && reg >= PCI_CAP_PCIE_START) {
+		reg -= PCI_CAP_PCIE_START;
+		read_op = bridge->ops->read_pcie;
+		cfgspace = (u32 *) &bridge->pcie_conf;
+		behavior = pcie_cap_regs_behavior;
+	} else {
+		read_op = bridge->ops->read_base;
+		cfgspace = (u32 *) &bridge->conf;
+		behavior = pci_regs_behavior;
+	}
+
+	if (read_op)
+		ret = read_op(bridge, reg, value);
+	else
+		ret = PCI_BRIDGE_EMUL_NOT_HANDLED;
+
+	if (ret == PCI_BRIDGE_EMUL_NOT_HANDLED)
+		*value = cfgspace[reg / 4];
+
+	/*
+	 * Make sure we never return any reserved bit with a value
+	 * different from 0.
+	 */
+	*value &= ~behavior[reg / 4].rsvd;
+
+	if (size == 1)
+		*value = (*value >> (8 * (where & 3))) & 0xff;
+	else if (size == 2)
+		*value = (*value >> (8 * (where & 3))) & 0xffff;
+	else if (size != 4)
+		return PCIBIOS_BAD_REGISTER_NUMBER;
+
+	return PCIBIOS_SUCCESSFUL;
+}
+
+/*
+ * Should be called by the PCI controller driver when writing the PCI
+ * configuration space of the fake bridge. It will call back the
+ * ->ops->write_base or ->ops->write_pcie operations.
+ */
+int pci_bridge_emul_conf_write(struct pci_bridge_emul *bridge, int where,
+			       int size, u32 value)
+{
+	int reg = where & ~3;
+	int mask, ret, old, new, shift;
+	void (*write_op)(struct pci_bridge_emul *bridge, int reg,
+			 u32 old, u32 new, u32 mask);
+	u32 *cfgspace;
+	const struct pci_bridge_reg_behavior *behavior;
+
+	if (bridge->has_pcie && reg >= PCI_CAP_PCIE_END)
+		return PCIBIOS_SUCCESSFUL;
+
+	if (!bridge->has_pcie && reg >= PCI_BRIDGE_CONF_END)
+		return PCIBIOS_SUCCESSFUL;
+
+	shift = (where & 0x3) * 8;
+
+	if (size == 4)
+		mask = 0xffffffff;
+	else if (size == 2)
+		mask = 0xffff << shift;
+	else if (size == 1)
+		mask = 0xff << shift;
+	else
+		return PCIBIOS_BAD_REGISTER_NUMBER;
+
+	ret = pci_bridge_emul_conf_read(bridge, reg, 4, &old);
+	if (ret != PCIBIOS_SUCCESSFUL)
+		return ret;
+
+	if (bridge->has_pcie && reg >= PCI_CAP_PCIE_START) {
+		reg -= PCI_CAP_PCIE_START;
+		write_op = bridge->ops->write_pcie;
+		cfgspace = (u32 *) &bridge->pcie_conf;
+		behavior = pcie_cap_regs_behavior;
+	} else {
+		write_op = bridge->ops->write_base;
+		cfgspace = (u32 *) &bridge->conf;
+		behavior = pci_regs_behavior;
+	}
+
+	/* Keep all bits, except the RW bits */
+	new = old & (~mask | ~behavior[reg / 4].rw);
+
+	/* Update the value of the RW bits */
+	new |= (value << shift) & (behavior[reg / 4].rw & mask);
+
+	/* Clear the W1C bits */
+	new &= ~((value << shift) & (behavior[reg / 4].w1c & mask));
+
+	cfgspace[reg / 4] = new;
+
+	if (write_op)
+		write_op(bridge, reg, old, new, mask);
+
+	return PCIBIOS_SUCCESSFUL;
+}
diff --git a/drivers/pci/pci-bridge-emul.h b/drivers/pci/pci-bridge-emul.h
new file mode 100644
index 000000000000..9d510ccf738b
--- /dev/null
+++ b/drivers/pci/pci-bridge-emul.h
@@ -0,0 +1,124 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PCI_BRIDGE_EMUL_H__
+#define __PCI_BRIDGE_EMUL_H__
+
+#include <linux/kernel.h>
+
+/* PCI configuration space of a PCI-to-PCI bridge. */
+struct pci_bridge_emul_conf {
+	u16 vendor;
+	u16 device;
+	u16 command;
+	u16 status;
+	u32 class_revision;
+	u8 cache_line_size;
+	u8 latency_timer;
+	u8 header_type;
+	u8 bist;
+	u32 bar[2];
+	u8 primary_bus;
+	u8 secondary_bus;
+	u8 subordinate_bus;
+	u8 secondary_latency_timer;
+	u8 iobase;
+	u8 iolimit;
+	u16 secondary_status;
+	u16 membase;
+	u16 memlimit;
+	u16 pref_mem_base;
+	u16 pref_mem_limit;
+	u32 prefbaseupper;
+	u32 preflimitupper;
+	u16 iobaseupper;
+	u16 iolimitupper;
+	u8 capabilities_pointer;
+	u8 reserve[3];
+	u32 romaddr;
+	u8 intline;
+	u8 intpin;
+	u16 bridgectrl;
+};
+
+/* PCI configuration space of the PCIe capabilities */
+struct pci_bridge_emul_pcie_conf {
+	u8 cap_id;
+	u8 next;
+	u16 cap;
+	u32 devcap;
+	u16 devctl;
+	u16 devsta;
+	u32 lnkcap;
+	u16 lnkctl;
+	u16 lnksta;
+	u32 slotcap;
+	u16 slotctl;
+	u16 slotsta;
+	u16 rootctl;
+	u16 rsvd;
+	u32 rootsta;
+	u32 devcap2;
+	u16 devctl2;
+	u16 devsta2;
+	u32 lnkcap2;
+	u16 lnkctl2;
+	u16 lnksta2;
+	u32 slotcap2;
+	u16 slotctl2;
+	u16 slotsta2;
+};
+
+struct pci_bridge_emul;
+
+typedef enum { PCI_BRIDGE_EMUL_HANDLED,
+	       PCI_BRIDGE_EMUL_NOT_HANDLED } pci_bridge_emul_read_status_t;
+
+struct pci_bridge_emul_ops {
+	/*
+	 * Called when reading from the regular PCI bridge
+	 * configuration space. Return PCI_BRIDGE_EMUL_HANDLED when the
+	 * operation has handled the read operation and filled in the
+	 * *value, or PCI_BRIDGE_EMUL_NOT_HANDLED when the read should
+	 * be emulated by the common code by reading from the
+	 * in-memory copy of the configuration space.
+	 */
+	pci_bridge_emul_read_status_t (*read_base)(struct pci_bridge_emul *bridge,
+						   int reg, u32 *value);
+
+	/*
+	 * Same as ->read_base(), except it is for reading from the
+	 * PCIe capability configuration space.
+	 */
+	pci_bridge_emul_read_status_t (*read_pcie)(struct pci_bridge_emul *bridge,
+						   int reg, u32 *value);
+	/*
+	 * Called when writing to the regular PCI bridge configuration
+	 * space. old is the current value, new is the new value being
+	 * written, and mask indicates which parts of the value are
+	 * being changed.
+	 */
+	void (*write_base)(struct pci_bridge_emul *bridge, int reg,
+			   u32 old, u32 new, u32 mask);
+
+	/*
+	 * Same as ->write_base(), except it is for writing from the
+	 * PCIe capability configuration space.
+	 */
+	void (*write_pcie)(struct pci_bridge_emul *bridge, int reg,
+			   u32 old, u32 new, u32 mask);
+};
+
+struct pci_bridge_emul {
+	struct pci_bridge_emul_conf conf;
+	struct pci_bridge_emul_pcie_conf pcie_conf;
+	struct pci_bridge_emul_ops *ops;
+	void *data;
+	bool has_pcie;
+};
+
+void pci_bridge_emul_init(struct pci_bridge_emul *bridge);
+int pci_bridge_emul_conf_read(struct pci_bridge_emul *bridge, int where,
+			      int size, u32 *value);
+int pci_bridge_emul_conf_write(struct pci_bridge_emul *bridge, int where,
+			       int size, u32 value);
+
+#endif /* __PCI_BRIDGE_EMUL_H__ */