melonDS/src/DMA_Timings.cpp

/*
    Copyright 2016-2023 melonDS team

    This file is part of melonDS.

    melonDS is free software: you can redistribute it and/or modify it under
    the terms of the GNU General Public License as published by the Free
    Software Foundation, either version 3 of the License, or (at your option)
    any later version.

    melonDS 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 melonDS. If not, see http://www.gnu.org/licenses/.
*/

#include "DMA_Timings.h"
#include "types.h"

namespace melonDS::DMATiming
{

// DMA timing tables
//
// DMA timings on the DS are normally straightforward, except in one case: when
// main RAM is involved.
// Main RAM to main RAM is the easy case: 16c/unit in 16bit mode, 18c/unit in 32bit
// mode.
// It gets more complicated when transferring from main RAM to somewhere else, or
// vice versa: main RAM supports burst accesses, but the rules dictating how long
// bursts can be are weird and inconsistent. Main RAM also supports parallel
// memory operations, to some extent.
// I haven't figured out the full logic behind it, let alone how to emulate it
// efficiently, so for now we will use these tables.
// A zero denotes the end of a burst pattern.
//
// Note: burst patterns only apply when the main RAM address is incrementing.
// A fixed or decrementing address results in nonsequential accesses.
//
// Note about GBA slot/wifi timings: these take into account the sequential timing
// setting. Timings are such that the nonseq setting only matters for the first
// access, and minor edge cases (like the last of a 0x20000-byte block).

extern const std::array<u8, 256> MRAMDummy = {0};

extern const std::array<u8, 256> MRAMRead16Bursts[] =
{
    // main RAM to regular 16bit or 32bit bus (similar)
    {7, 3, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2,
     7, 3, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2,
     7, 3,
     0},
    // main RAM to GBA/wifi, seq=4
    {8, 6, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5,
     0},
    // main RAM to GBA/wifi, seq=6
    {10, 8, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7,
     12, 8, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7,
     12, 8, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7,
     12, 8, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7,
     12, 8, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7,
     12, 8, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7,
     12, 8, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7,
     12, 8,
     0},
};

extern const std::array<u8, 256> MRAMRead32Bursts[] =
{
    // main RAM to regular 16bit bus
    {9, 4, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 9,
     0},
    // main RAM to regular 32bit bus
    {9, 3, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2,
     0},
    // main RAM to GBA/wifi, seq=4
    {14, 10, 9, 9, 9, 9, 9, 9, 9, 9,
     9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
     9, 9, 9, 9, 9, 9, 9,
     13, 10, 9, 9, 9, 9, 9, 9, 9, 9,
     9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
     9, 9, 9, 9, 9, 9, 9,
     13, 10, 9, 9, 9, 9, 9, 9, 9, 9,
     9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
     9, 9, 9, 9, 9, 9, 9,
     13, 10, 9, 9, 9, 9, 9, 9, 9, 9,
     9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
     9, 9, 9, 9, 9, 9, 9,
     13, 10, 9, 9, 9, 9, 9, 9, 9, 9,
     9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
     9, 9, 9, 9, 9, 9, 9,
     13,
     0},
    // main RAM to GBA/wifi, seq=6
    {18, 14, 13, 13, 13, 13, 13, 13, 13, 13,
     13, 13, 13, 13, 13, 13, 13, 13, 13,
     17, 14, 13, 13, 13, 13, 13, 13, 13, 13,
     13, 13, 13, 13, 13, 13, 13, 13, 13,
     17, 14, 13, 13, 13, 13, 13, 13, 13, 13,
     13, 13, 13, 13, 13, 13, 13, 13, 13,
     17, 14, 13, 13, 13, 13, 13, 13, 13, 13,
     13, 13, 13, 13, 13, 13, 13, 13, 13,
     17, 14, 13, 13, 13, 13, 13, 13, 13, 13,
     13, 13, 13, 13, 13, 13, 13, 13, 13,
     17,
     0},
};

extern const std::array<u8, 256> MRAMWrite16Bursts[] =
{
    // regular 16bit or 32bit bus to main RAM (similar)
    {8, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     0},
    // GBA/wifi to main RAM, seq=4
    {10, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
     5, 5, 5, 5, 5, 5, 5, 5,
     0},
    // GBA/wifi to main RAM, seq=6
    {9, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
     7, 7, 7, 7, 7,
     0},
};

extern const std::array<u8, 256> MRAMWrite32Bursts[4] =
{
    // regular 16bit bus to main RAM
    {9, 4, 4, 4, 4, 4, 4, 4, 4, 4,
     4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
     4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
     4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
     4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
     4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
     0},
    // regular 32bit bus to main RAM
    {9, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
     0},
    // GBA/wifi to main RAM, seq=4
    {15, 10, 10, 10, 10, 10, 10, 10, 10, 10,
     10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
     10, 10, 10, 10,
     0},
    // GBA/wifi to main RAM, seq=6
    {16, 14, 14, 14, 14, 14, 14, 14, 14, 14,
     14, 14, 14, 14, 14, 14, 14, 14,
     0},
};

}