// 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)

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),
        },
};

/*
 * 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.
 */
int pci_bridge_emul_init(struct pci_bridge_emul *bridge,
                         unsigned int flags)
{
        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;
        bridge->pci_regs_behavior = kmemdup(pci_regs_behavior,
                                            sizeof(pci_regs_behavior),
                                            GFP_KERNEL);
        if (!bridge->pci_regs_behavior)
                return -ENOMEM;

        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;
                bridge->pcie_cap_regs_behavior =
                        kmemdup(pcie_cap_regs_behavior,
                                sizeof(pcie_cap_regs_behavior),
                                GFP_KERNEL);
                if (!bridge->pcie_cap_regs_behavior) {
                        kfree(bridge->pci_regs_behavior);
                        return -ENOMEM;
                }
        }

        if (flags & PCI_BRIDGE_EMUL_NO_PREFETCHABLE_BAR) {
                bridge->pci_regs_behavior[PCI_PREF_MEMORY_BASE / 4].ro = ~0;
                bridge->pci_regs_behavior[PCI_PREF_MEMORY_BASE / 4].rw = 0;
        }

        return 0;
}

/*
 * Cleanup a pci_bridge_emul structure that was previously initialized
 * using pci_bridge_emul_init().
 */
void pci_bridge_emul_cleanup(struct pci_bridge_emul *bridge)
{
        if (bridge->has_pcie)
                kfree(bridge->pcie_cap_regs_behavior);
        kfree(bridge->pci_regs_behavior);
}

/*
 * 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 = bridge->pcie_cap_regs_behavior;
        } else {
                read_op = bridge->ops->read_base;
                cfgspace = (u32 *) &bridge->conf;
                behavior = bridge->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 = bridge->pcie_cap_regs_behavior;
        } else {
                write_op = bridge->ops->write_base;
                cfgspace = (u32 *) &bridge->conf;
                behavior = bridge->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;
}