path: root/bus.cpp

/* SPDX-License-Identifier: Unlicense
 */

#include "bus.hpp"
#include "musashi-m68k/m68k.h"
#include "utils.hpp"
#include "vdp.hpp"
#include "io.hpp"

#include <cassert>
#include <cstdarg>
#include <cstdbool>
#include <cstdio>
#include <cstdint>
#include <cstdlib>
#include <vector>

#if !defined(DEBUG_TRACE_VDP_ACCESS)
#   define DEBUG_TRACE_VDP_ACCESS 0
#endif

namespace Adr {
static constexpr uint32_t kZ80BusReq = 0x00a11100;
static constexpr uint32_t kZ80Reset = 0x00a11200;
}

extern void m68k_breakpoint_callback(void);

extern unsigned char g_rom[ROM_SIZE];
extern unsigned char g_ram[RAM_SIZE];
extern unsigned char g_sound_ram[SOUND_RAM_SIZE];
extern IO g_io1;
extern unsigned char g_io2[VDP_SIZE];
extern unsigned char g_psg[PSG_SIZE];
extern VDP g_vdp;
extern std::vector<Breakpoint> code_bkpts, read_bkpts, write_bkpts, access_bkpts;

static void exit_error(const char* fmt, ...)
{
    static bool in_error = false;
    if (in_error)
    {
        fprintf(stderr, "Nested error\n");
        return;
    }
    in_error = true;
    va_list args;
    va_start(args, fmt);
    vfprintf(stderr, fmt, args);
    va_end(args);
    fprintf(stderr, "\n");
    unsigned int pc = m68k_get_reg(NULL, M68K_REG_PPC);
    char buff[100]{};
    m68k_disassemble(buff, pc, M68K_CPU_TYPE_68000);
    fprintf(stderr, "%08x: %s\n", pc, buff);
    exit(EXIT_FAILURE);
}

static void report_error(const char* fmt, ...)
{
    static bool in_error = false;
    if (in_error)
        return;
    in_error = true;
    va_list args;
    va_start(args, fmt);
    vfprintf(stderr, fmt, args);
    va_end(args);
    fprintf(stderr, "\n");
    unsigned int pc = m68k_get_reg(NULL, M68K_REG_PPC);
    char buff[100]{};
    m68k_disassemble(buff, pc, M68K_CPU_TYPE_68000);
    fprintf(stderr, "%08x: %s\n", pc, buff);
    in_error = false;
}

static inline bool is_in_range(uint32_t value, uint32_t begin, uint32_t length)
{
    return value >= begin && value <= begin + length;
}

struct ReadResult {
    unsigned int result;
    bool successful;
};

static inline unsigned int memory_read_concrete(
        const enum bitness bitness,
        unsigned char const * base,
        const uint32_t address)
{
    switch (bitness) {
    case BITNESS_8:
        return base[address];
    case BITNESS_16:
        return (base[address] << 8) | base[address + 1];
    case BITNESS_32:
        return (base[address] << 24) |
            (base[address + 1] << 16) |
            (base[address + 2] << 8) |
            base[address + 3];
    }
    UNREACHABLE;
}

static inline bool ranges_overlap(
        const uint32_t a_start,
        const uint32_t a_len,
        const uint32_t b_start,
        const uint32_t b_len)
{
    return (a_start < b_start + b_len && b_start < a_start + a_len);
}

static inline void m68k_read_callback(const uint32_t address, const uint32_t size)
{
    for (size_t bi = 0; bi < access_bkpts.size(); bi++) {
        const auto& b = access_bkpts[bi];
        if (ranges_overlap(address, size, b.offset, b.length)) {
            printf("Access watchpoint @ 0x%08x\n", address);
            m68k_breakpoint_callback();
            break;
        }
    }
    for (size_t bi = 0; bi < read_bkpts.size(); bi++) {
        const auto& b = read_bkpts[bi];
        if (ranges_overlap(address, size, b.offset, b.length)) {
            printf("Read watchpoint @ 0x%08x\n", address);
            m68k_breakpoint_callback();
            break;
        }
    }
}

static inline ReadResult memory_read(
        const enum bitness bitness,
        const uint32_t address)
{
    m68k_read_callback(address, bitness);
    if (is_in_range(address, ROM_START, ROM_SIZE)) {
        return ReadResult{
            memory_read_concrete(bitness, g_rom, address - ROM_START),
            true,
        };
    } else if (is_in_range(address, RAM_START, RAM_SIZE)) {
        return ReadResult{
            memory_read_concrete(bitness, g_ram, address - RAM_START),
            true,
        };
    } else if (is_in_range(address, SOUND_RAM_START, SOUND_RAM_SIZE)) {
        if (DEBUG_TRACE_Z80RAM_ACCESS) {
            printf(
                    "Z80RAM r%d%s @0x%08x\n",
                    bitness * 8,
                    (bitness <= 1 ? " " : ""),
                    SOUND_RAM_START + address);
        }
        return ReadResult{
            memory_read_concrete(bitness, g_sound_ram, address - SOUND_RAM_START),
            true,
        };
    } else if (is_in_range(address, IO1_START, IO1_SIZE)) {
        return ReadResult{
            g_io1.Read(address - g_io1.base_address, bitness),
            true,
        };
    } else if (is_in_range(address, VDP_START, VDP_SIZE)) {
        if (address == PSG_START) {
            if (DEBUG_TRACE_PSG_ACCESS) {
                printf(
                        "PSG r%d%s @0x%08x\n",
                        bitness * 8,
                        (bitness <= 1 ? " " : ""),
                        PSG_START + address);
            }
            // XXX PSG does not seem necessary to implement
            return ReadResult{ g_psg[0], true };
        }
        return ReadResult{
            g_vdp.Read(address - g_vdp.base_address, bitness),
            true,
        };
    }
    return ReadResult{0, false};
}

static inline void memory_write_concrete(
        enum bitness bitness,
        unsigned char * const base,
        const uint32_t address,
        const unsigned int value)
{
    switch (bitness) {
    case BITNESS_8:
        base[address] = value & 0xff;
        break;
    case BITNESS_16:
        base[address + 0] = (value >> 8) & 0xff;
        base[address + 1] = value & 0xff;
        break;
    case BITNESS_32:
        base[address + 0] = (value >> 24) & 0xff;
        base[address + 1] = (value >> 16) & 0xff;
        base[address + 2] = (value >> 8) & 0xff;
        base[address + 3] = value & 0xff;
        break;
    }
}

static inline void m68k_write_callback(const uint32_t address, const uint32_t size)
{
    for (size_t bi = 0; bi < access_bkpts.size(); bi++) {
        const auto& b = access_bkpts[bi];
        if (ranges_overlap(address, size, b.offset, b.length)) {
            printf("Access watchpoint @ 0x%08x\n", address);
            m68k_breakpoint_callback();
            break;
        }
    }
    for (size_t bi = 0; bi < write_bkpts.size(); bi++) {
        const auto& b = write_bkpts[bi];
        if (ranges_overlap(address, size, b.offset, b.length)) {
            printf("Write watchpoint @ 0x%08x\n", address);
            m68k_breakpoint_callback();
            break;
        }
    }
}

static inline bool memory_write(
        const enum bitness bitness,
        const uint32_t address,
        const unsigned int value)
{
    m68k_write_callback(address, bitness);
    if (is_in_range(address, ROM_START, ROM_SIZE)) {
        memory_write_concrete(bitness, g_rom, address - ROM_START, value);
        return true;
    } else if (is_in_range(address, RAM_START, RAM_SIZE)) {
        memory_write_concrete(bitness, g_ram, address - RAM_START, value);
        return true;
    } else if (is_in_range(address, SOUND_RAM_START, SOUND_RAM_SIZE)) {
        if (DEBUG_TRACE_Z80RAM_ACCESS) {
            printf(
                    "Z80RAM w%d%s @0x%08x 0x%0*x\n",
                    bitness * 8,
                    (bitness <= 1 ? " " : ""),
                    SOUND_RAM_START + address,
                    bitness * 2,
                    value);
        }
        memory_write_concrete(bitness, g_sound_ram, address - SOUND_RAM_START, value);
        return true;
    } else if (is_in_range(address, IO1_START, IO1_SIZE)) {
        g_io1.Write(address - g_io1.base_address, bitness, value);
        return true;
    } else if (is_in_range(address, VDP_START, VDP_SIZE)) {
        if (address == PSG_START) {
            if (DEBUG_TRACE_PSG_ACCESS) {
                printf(
                        "PSG w%d%s @0x%08x 0x%0*x\n",
                        bitness * 8,
                        (bitness <= 1 ? " " : ""),
                        PSG_START + address,
                        bitness * 2,
                        value);
            }
            // XXX PSG does not seem necessary to implement
            g_psg[0] = value & 0xff;
            return true;
        }
        g_vdp.Write(address - g_vdp.base_address, bitness, value);
        return true;
    }
    return false;
}

#define MASK_24(X) ((X) & 0x00ffffff)

unsigned int m68k_read_memory_8(const unsigned int address_a)
{
    const uint32_t address = MASK_24(address_a);
    const ReadResult ret = memory_read(BITNESS_8, address);
    if (!ret.successful) {
        report_error("Read error u8 @%08x", address);
        m68k_breakpoint_callback();
    }
    return ret.result;
}

unsigned int m68k_read_memory_16(const unsigned int address_a)
{
    const uint32_t address = MASK_24(address_a);
    const ReadResult ret = memory_read(BITNESS_16, address);
    if (!ret.successful) {
        report_error("Read error u16 @%08x", address);
        m68k_breakpoint_callback();
    }
    return ret.result;
}

unsigned int m68k_read_memory_32(const unsigned int address_a)
{
    const uint32_t address = MASK_24(address_a);
    const ReadResult ret = memory_read(BITNESS_32, address);
    if (!ret.successful) {
        report_error("Read error u32 @%08x", address);
        m68k_breakpoint_callback();
    }
    return ret.result;
}

unsigned int m68k_read_disassembler_16(const unsigned int address_a)
{
    const uint32_t address = MASK_24(address_a);
    const ReadResult ret = memory_read(BITNESS_16, address);
    if (0 && !ret.successful)
        exit_error("Disasm read error u16 @0x%08x", address);
    return ret.result;
}

unsigned int m68k_read_disassembler_32(const unsigned int address_a)
{
    const uint32_t address = MASK_24(address_a);
    const ReadResult ret = memory_read(BITNESS_32, address);
    if (0 && !ret.successful)
        exit_error("Disasm read error u32 @0x%08x", address);
    return ret.result;
}

void m68k_write_memory_8(const unsigned int address_a, const unsigned int value)
{
    const uint32_t address = MASK_24(address_a);
    const bool successful = memory_write(BITNESS_8, address, value);
    if (!successful) {
        report_error("Attempted to write 0x%02x (u8) to address %08x", value&0xff, address);
        m68k_breakpoint_callback();
    }
}

void m68k_write_memory_16(const unsigned int address_a, const unsigned int value)
{
    const uint32_t address = MASK_24(address_a);
    const bool successful = memory_write(BITNESS_16, address, value);
    if (!successful) {
        report_error("Attempted to write 0x%04x (u16) to address %08x", value&0xff, address);
        m68k_breakpoint_callback();
    }
}

void m68k_write_memory_32(const unsigned int address_a, const unsigned int value)
{
    const uint32_t address = MASK_24(address_a);
    const bool successful = memory_write(BITNESS_32, address, value);
    if (!successful) {
        report_error("Attempted to write 0x%08x (u32) to address %08x", value&0xff, address);
        m68k_breakpoint_callback();
    }
}