bsnes-patches/v085/0027-Bus-fixes-Do-not-update-MDR-on-read-from-CPU-MMIO-sp.patch

   1 From 4cfbbeadc3abe3e3911f7f59ce57b715edc76563 Mon Sep 17 00:00:00 2001
   2 From: Ilari Liusvaara <ilariliusvaara@welho.com>
   3 Date: Wed, 25 Oct 2017 14:18:34 +0300
   4 Subject: [PATCH 27/27] Bus fixes: Do not update MDR on read from CPU MMIO
   5  space
   6
   7 Also, updates the controller read timings to be more accurate.
   8 ---
   9  snes/config/config.cpp     |   1 +
  10  snes/config/config.hpp     |   1 +
  11  snes/cpu/cpu.cpp           |   2 +
  12  snes/cpu/memory/memory.cpp |  26 ++++++++-
  13  snes/cpu/mmio/mmio.cpp     |  14 +++--
  14  snes/cpu/timing/joypad.cpp | 132 +++++++++++++++++++++++++++++++++++++++------
  15  snes/cpu/timing/timing.cpp |  11 ++--
  16  snes/cpu/timing/timing.hpp |   3 +-
  17  snes/snes.hpp              |   1 +
  18  9 files changed, 166 insertions(+), 25 deletions(-)
  19
  20 diff --git a/snes/config/config.cpp b/snes/config/config.cpp
  21 index 19831370..8dcfd7e8 100755
  22 --- a/snes/config/config.cpp
  23 +++ b/snes/config/config.cpp
  24 @@ -15,6 +15,7 @@ Configuration::Configuration() {
  25    cpu.pal_frequency   = 21281370;
  26    cpu.wram_init_value = 0x55;
  27    cpu.alt_poll_timings = false;
  28 +  cpu.bus_fixes = false;
  29
  30    smp.ntsc_frequency = 24607104;   //32040.5 * 768
  31    smp.pal_frequency  = 24607104;
  32 diff --git a/snes/config/config.hpp b/snes/config/config.hpp
  33 index 68fe0bde..d8577e39 100755
  34 --- a/snes/config/config.hpp
  35 +++ b/snes/config/config.hpp
  36 @@ -14,6 +14,7 @@ struct Configuration {
  37      unsigned pal_frequency;
  38      unsigned wram_init_value;
  39      bool alt_poll_timings;
  40 +    bool bus_fixes;
  41    } cpu;
  42
  43    struct SMP {
  44 diff --git a/snes/cpu/cpu.cpp b/snes/cpu/cpu.cpp
  45 index e11fc882..5e8e3137 100755
  46 --- a/snes/cpu/cpu.cpp
  47 +++ b/snes/cpu/cpu.cpp
  48 @@ -1,5 +1,7 @@
  49  #include <snes/snes.hpp>
  50  #include <cstdio>
  51 +#include <iostream>
  52 +#include <cassert>
  53
  54  #define CPU_CPP
  55  namespace SNES {
  56 diff --git a/snes/cpu/memory/memory.cpp b/snes/cpu/memory/memory.cpp
  57 index 31f82c31..df439c22 100755
  58 --- a/snes/cpu/memory/memory.cpp
  59 +++ b/snes/cpu/memory/memory.cpp
  60 @@ -14,10 +14,32 @@ uint8 CPU::op_read(uint32 addr, bool exec) {
  61    status.clock_count = speed(addr);
  62    dma_edge();
  63    add_clocks(status.clock_count - 4);
  64 -  regs.mdr = bus.read(addr, exec);
  65 +  //MDR presents the state held by parasitic capacitance of the external bus.
  66 +  //This bus is not affected by reads from CPU-internal registers, only if
  67 +  //some external device responds. SDD1 does hook some of these addresses, but
  68 +  //passes read straight through, as expected (as the CPU probably won't
  69 +  //monitor if external device responds, even if it broadcasts a read).
  70 +  //
  71 +  //We use 4000-43FF as CPU register range, and not 4000-437F it likely is
  72 +  //for quickness of checking. This will only affect things if some device
  73 +  //tries to map the 4380-43FF range (that device will still work correctly,
  74 +  //but openbus in that range won't).
  75 +  //
  76 +  //This was discovered while investigating why one Super Metroid glitch
  77 +  //worked on emulator but crashed on real console.
  78 +  //
  79 +  //a word fetch from 2f4017 AND 0xfffc results in 2f3c and a word fetch from
  80 +  //2f4210 AND 0x7f7f results in 2f22. This also extends to long fetches
  81 +  //by arguments. E.g. long argument fetch from 94420F with 2F already on
  82 +  //the bus AND 0x7f7fff results in 2f222f.
  83 +  //
  84 +  //The reason for masking some bits in above explanation was to ignore some
  85 +  //known bits in those registers (bits 7 of 4210 and 4211, bits 0&1 of 4017).
  86 +  uint8_t tmp = bus.read(addr, exec);
  87 +  if(!config.cpu.bus_fixes || (addr & 0x40FC00) != 0x004000) regs.mdr = tmp;
  88    add_clocks(4);
  89    alu_edge();
  90 -  return regs.mdr;
  91 +  return tmp;
  92  }
  93
  94  void CPU::op_write(uint32 addr, uint8 data) {
  95 diff --git a/snes/cpu/mmio/mmio.cpp b/snes/cpu/mmio/mmio.cpp
  96 index 30048c19..be2990a3 100755
  97 --- a/snes/cpu/mmio/mmio.cpp
  98 +++ b/snes/cpu/mmio/mmio.cpp
  99 @@ -33,9 +33,17 @@ void CPU::mmio_w2183(uint8 data) {
 100  //strobing $4016.d0 affects both controller port latches.
 101  //$4017 bit 0 writes are ignored.
 102  void CPU::mmio_w4016(uint8 data) {
 103 -  if(data&1) interface->notifyLatched();
 104 -  input.port1->latch(data & 1);
 105 -  input.port2->latch(data & 1);
 106 +  //Only consider autoassert if both busfix and auto flags are set.
 107 +  auto auto_asserted = (status.auto_joypad_counter & 384) == 384;
 108 +  //Bit 6 of status.auto_joypad_counter follows "manual" latch.
 109 +  auto oldstatus = auto_asserted || (status.auto_joypad_counter & 64) != 0;
 110 +  status.auto_joypad_counter &= ~64;
 111 +  status.auto_joypad_counter |= (data & 1) << 6;
 112 +  auto newstatus = auto_asserted || (status.auto_joypad_counter & 64) != 0;
 113 +  //If !oldstatus and newstatus, signal latch.
 114 +  if(!oldstatus && newstatus) interface->notifyLatched();
 115 +  input.port1->latch(newstatus);
 116 +  input.port2->latch(newstatus);
 117  }
 118
 119  //JOYSER0
 120 diff --git a/snes/cpu/timing/joypad.cpp b/snes/cpu/timing/joypad.cpp
 121 index afca7504..b60be020 100755
 122 --- a/snes/cpu/timing/joypad.cpp
 123 +++ b/snes/cpu/timing/joypad.cpp
 124 @@ -3,11 +3,14 @@
 125  //called every 256 clocks; see CPU::add_clocks()
 126  void CPU::step_auto_joypad_poll() {
 127    if(vcounter() >= (ppu.overscan() == false ? 225 : 240)) {
 128 +    auto cycle = status.auto_joypad_counter & 63;
 129      //cache enable state at first iteration
 130 -    if(status.auto_joypad_counter == 0) status.auto_joypad_latch = status.auto_joypad_poll;
 131 -    status.auto_joypad_active = status.auto_joypad_counter <= 15;
 132 +    if(cycle == 0) status.auto_joypad_latch = status.auto_joypad_poll;
 133 +    status.auto_joypad_active = cycle <= 15;
 134      if(status.auto_joypad_active && status.auto_joypad_latch) {
 135 -      if(status.auto_joypad_counter == 0) {
 136 +      if(cycle == 0) {
 137 +        if(status.auto_joypad_counter & 128)
 138 +          std::cerr << "step_auto_joypad_poll(): bus fixes set (counter=" << status.auto_joypad_counter << ")???" << std::endl;
 139          if(dma_trace_fn) dma_trace_fn("-- Start automatic polling --");
 140          interface->notifyLatched();
 141          input.port1->latch(1);
 142 @@ -23,7 +26,7 @@ void CPU::step_auto_joypad_poll() {
 143        status.joy2 = (status.joy2 << 1) | (bool)(port1 & 1);
 144        status.joy3 = (status.joy3 << 1) | (bool)(port0 & 2);
 145        status.joy4 = (status.joy4 << 1) | (bool)(port1 & 2);
 146 -      if(status.auto_joypad_counter == 15) {
 147 +      if(cycle == 15) {
 148          char buf[512];
 149          sprintf(buf, "-- End automatic polling [%04x %04x %04x %04x] --",
 150            status.joy1, status.joy2, status.joy3, status.joy4);
 151 @@ -31,32 +34,129 @@ void CPU::step_auto_joypad_poll() {
 152        }
 153      }
 154
 155 -    status.auto_joypad_counter++;
 156 +    //Only bits 0-5 are supposed to increment.
 157 +    if(cycle < 60)
 158 +      status.auto_joypad_counter++;
 159    }
 160  }
 161
 162  //called every 128 clocks; see CPU::add_clocks()
 163 -void CPU::step_auto_joypad_poll_NEW(bool polarity) {
 164 -  if(status.auto_joypad_counter > 0 && status.auto_joypad_counter <= 34) {
 165 +void CPU::step_auto_joypad_poll_NEW2(bool polarity) {
 166 +  //Poll starts on multiple of 128 mod 256 clocks (polarity=false) on first
 167 +  //vblank scanline. If autopoller is off, mark as done for the frame.
 168 +  if(vcounter() >= (ppu.overscan() == false ? 225 : 240) && !polarity &&
 169 +    (status.auto_joypad_counter & 63) == 0) {
 170 +    if(!(status.auto_joypad_counter & 128))
 171 +      std::cerr << "step_auto_joypad_poll_NEW2(): bus fixes clear???" << std::endl;
 172 +    //Preserve high bits of autopoll counter.
 173 +    auto x = status.auto_joypad_counter & ~63;
 174 +    status.auto_joypad_counter = x | (status.auto_joypad_poll ? 1 : 36);
 175 +    status.auto_joypad_latch = status.auto_joypad_poll;
 176 +  }
 177 +  //Abuse bit 6 of counter for "manual" poll flag. Bit 7 is supposed to be
 178 +  //always set.
 179 +  auto cycle = status.auto_joypad_counter & 63;
 180 +  auto old_latchstate = (status.auto_joypad_counter & 320) != 0;
 181 +  //If not enabled... This is not latched, as autopoll can be aborted.
 182 +  if(!status.auto_joypad_poll && cycle > 0 && cycle < 36) {
 183 +    if(dma_trace_fn) dma_trace_fn("-- Automatic polling ABORTED --");
 184 +    status.auto_joypad_counter += (36 - cycle);
 185 +    status.auto_joypad_active = false;
 186 +    status.auto_joypad_latch = false;
 187 +    //Release autopoll latch.
 188 +    status.auto_joypad_counter &= ~256;        //Autopoll clears latch.
 189 +    auto new_latchstate = (status.auto_joypad_counter & 320) != 0;
 190 +    if(old_latchstate && !new_latchstate) {
 191 +      input.port1->latch(0);
 192 +      input.port2->latch(0);
 193 +    }
 194 +    return;
 195 +  }
 196 +  //On cycle #1, latch is asserted (unless latch is already high, in this
 197 +  //case the autopoller is supposed to force latch high too).
 198 +  if(cycle == 1) {
 199 +    if(dma_trace_fn) dma_trace_fn("-- Start automatic polling --");
 200 +    //Assert autopoll latch.
 201 +    status.auto_joypad_counter |= 256;
 202 +    auto new_latchstate = (status.auto_joypad_counter & 320) != 0;
 203 +    if(!old_latchstate && new_latchstate) {
 204 +      interface->notifyLatched();
 205 +      input.port1->latch(1);
 206 +      input.port2->latch(1);
 207 +    }
 208 +  }
 209 +  //On cycle #2, busy is asserted and controllers are cleared.
 210 +  if(cycle == 2) {
 211 +    status.joy1 = 0;
 212 +    status.joy2 = 0;
 213 +    status.joy3 = 0;
 214 +    status.joy4 = 0;
 215 +    status.auto_joypad_active = true;
 216 +  }
 217 +  //Then, on cycle #3, latch is deasserted, unless "manual" latch forces
 218 +  //real latch high.
 219 +  if(cycle == 3) {
 220 +    //Release autopoll latch.
 221 +    status.auto_joypad_counter &= ~256;
 222 +    auto new_latchstate = (status.auto_joypad_counter & 320) != 0;
 223 +    if(old_latchstate && !new_latchstate) {
 224 +      input.port1->latch(0);
 225 +      input.port2->latch(0);
 226 +    }
 227 +  }
 228 +  //Then on cycles #4, #6, #8, ..., #34, a bit is shifted. Also, clock would
 229 +  //go low, but we can not emulate that.
 230 +  if(cycle >= 4 && cycle <= 34 && cycle % 2 == 0) {
 231 +    uint2 port0 = input.port1->data();
 232 +    uint2 port1 = input.port2->data();
 233 +    status.joy1 = (status.joy1 << 1) | (bool)(port0 & 1);
 234 +    status.joy2 = (status.joy2 << 1) | (bool)(port1 & 1);
 235 +    status.joy3 = (status.joy3 << 1) | (bool)(port0 & 2);
 236 +    status.joy4 = (status.joy4 << 1) | (bool)(port1 & 2);
 237 +  }
 238 +  //Then on cycles #5, #7, #9, ..., #35, clock drops high, But we can not
 239 +  //emulate that.
 240 +  //Then on cycle #35, busy flag is deasserted and poll is complete.
 241 +  if(cycle == 35) {
 242 +    status.auto_joypad_active = false;
 243 +    char buf[512];
 244 +    sprintf(buf, "-- End automatic polling [%04x %04x %04x %04x] --",
 245 +      status.joy1, status.joy2, status.joy3, status.joy4);
 246 +    if(dma_trace_fn) dma_trace_fn(buf);
 247 +  }
 248 +  //The entiere train is 35 cycles.
 249 +  if(cycle > 0 && cycle < 36) {
 250 +      status.auto_joypad_counter++;
 251 +  }
 252 +}
 253 +
 254 +
 255 +//called every 128 clocks; see CPU::add_clocks()
 256 +void CPU::step_auto_joypad_poll_NEW(bool polarity, bool new2) {
 257 +  if(new2) return step_auto_joypad_poll_NEW2(polarity);
 258 +  auto cycle = status.auto_joypad_counter & 63;
 259 +  if(cycle > 0 && cycle <= 34) {
 260      if(!status.auto_joypad_latch) {
 261        //FIXME: Is this right, busy flag goes on even if not enabled???
 262 -      if(status.auto_joypad_counter == 1)
 263 +      if(cycle == 1)
 264          status.auto_joypad_active = true;
 265 -      if(status.auto_joypad_counter == 34)
 266 +      if(cycle == 34)
 267          status.auto_joypad_active = false;
 268      } else {
 269 -      if(status.auto_joypad_counter == 1) {
 270 +      if(cycle == 1) {
 271 +        if(status.auto_joypad_counter & 128)
 272 +          std::cerr << "step_auto_joypad_poll_NEW(): bus fixes set???" << std::endl;
 273          if(dma_trace_fn) dma_trace_fn("-- Start automatic polling --");
 274          status.auto_joypad_active = true;
 275          interface->notifyLatched();
 276          input.port1->latch(1);
 277          input.port2->latch(1);
 278        }
 279 -      if(status.auto_joypad_counter == 3) {
 280 +      if(cycle == 3) {
 281          input.port1->latch(0);
 282          input.port2->latch(0);
 283        }
 284 -      if((status.auto_joypad_counter & 1) != 0 &&  status.auto_joypad_counter != 1) {
 285 +      if((cycle & 1) != 0 && cycle != 1) {
 286          uint2 port0 = input.port1->data();
 287          uint2 port1 = input.port2->data();
 288
 289 @@ -65,7 +165,7 @@ void CPU::step_auto_joypad_poll_NEW(bool polarity) {
 290          status.joy3 = (status.joy3 << 1) | (bool)(port0 & 2);
 291          status.joy4 = (status.joy4 << 1) | (bool)(port1 & 2);
 292        }
 293 -      if(status.auto_joypad_counter == 34) {
 294 +      if(cycle == 34) {
 295          status.auto_joypad_active = false;
 296          char buf[512];
 297          sprintf(buf, "-- End automatic polling [%04x %04x %04x %04x] --",
 298 @@ -75,9 +175,11 @@ void CPU::step_auto_joypad_poll_NEW(bool polarity) {
 299      }
 300      status.auto_joypad_counter++;
 301    }
 302 -  if(vcounter() >= (ppu.overscan() == false ? 225 : 240) && status.auto_joypad_counter == 0 && !polarity) {
 303 +  if(vcounter() >= (ppu.overscan() == false ? 225 : 240) && cycle == 0 && !polarity) {
 304 +    //Preserve high bits of autopoller counter.
 305 +    auto x = status.auto_joypad_counter & ~63;
 306      status.auto_joypad_latch = status.auto_joypad_poll;
 307 -    status.auto_joypad_counter = 1;
 308 +    status.auto_joypad_counter = x | 1;
 309    }
 310  }
 311
 312 diff --git a/snes/cpu/timing/timing.cpp b/snes/cpu/timing/timing.cpp
 313 index d7cf24f3..ef81d891 100755
 314 --- a/snes/cpu/timing/timing.cpp
 315 +++ b/snes/cpu/timing/timing.cpp
 316 @@ -17,12 +17,12 @@ void CPU::add_clocks(unsigned clocks) {
 317
 318    step(clocks);
 319
 320 -  if(config.cpu.alt_poll_timings) {
 321 +  if(config.cpu.alt_poll_timings || config.cpu.bus_fixes) {
 322      bool opolarity = (status.auto_joypad_clock & 128);
 323      status.auto_joypad_clock = (status.auto_joypad_clock + clocks) & 0xFF;
 324      bool npolarity = (status.auto_joypad_clock & 128);
 325      if(opolarity != npolarity)
 326 -      step_auto_joypad_poll_NEW(opolarity);
 327 +      step_auto_joypad_poll_NEW(opolarity, config.cpu.bus_fixes);
 328    } else {
 329      status.auto_joypad_clock += clocks;
 330      if(status.auto_joypad_clock >= 256) {
 331 @@ -53,7 +53,8 @@ void CPU::scanline() {
 332      status.hdma_init_position = (cpu_version == 1 ? 12 + 8 - dma_counter() : 12 + dma_counter());
 333      status.hdma_init_triggered = false;
 334
 335 -    status.auto_joypad_counter = 0;
 336 +    //Only clear the low 6 bits (counter).
 337 +    status.auto_joypad_counter &= ~63;
 338    }
 339
 340    //DRAM refresh occurs once every scanline
 341 @@ -200,7 +201,9 @@ void CPU::timing_reset() {
 342
 343    status.auto_joypad_active  = false;
 344    status.auto_joypad_latch   = false;
 345 -  status.auto_joypad_counter = 0;
 346 +  //Set bit 7 of joypad counter if bus fixes are active (for combined
 347 +  //latch behavior).
 348 +  status.auto_joypad_counter = config.cpu.bus_fixes ? 128 : 0;
 349    status.auto_joypad_clock   = 0;
 350  }
 351
 352 diff --git a/snes/cpu/timing/timing.hpp b/snes/cpu/timing/timing.hpp
 353 index bf15a727..8be2b830 100755
 354 --- a/snes/cpu/timing/timing.hpp
 355 +++ b/snes/cpu/timing/timing.hpp
 356 @@ -22,4 +22,5 @@ alwaysinline bool irq_test();
 357
 358  //joypad.cpp
 359  void step_auto_joypad_poll();
 360 -void step_auto_joypad_poll_NEW(bool polarity);
 361 +void step_auto_joypad_poll_NEW(bool polarity, bool new2);
 362 +void step_auto_joypad_poll_NEW2(bool polarity);
 363 diff --git a/snes/snes.hpp b/snes/snes.hpp
 364 index 3a65e360..961842b3 100755
 365 --- a/snes/snes.hpp
 366 +++ b/snes/snes.hpp
 367 @@ -3,6 +3,7 @@
 368  #define BSNES_SUPPORTS_ADV_BREAKPOINTS
 369  #define BSNES_SUPPORTS_ADV_BREAKPOINTS_PPU
 370  #define BSNES_SUPPORTS_ALT_TIMINGS
 371 +#define BSNES_SUPPORTS_BUS_FIXES
 372  #define BSNES_SUPPORTS_TRACE_SA1
 373  #define BSNES_SUPPORTS_DMA_TRACE
 374
 375 --
 376 2.15.0.rc1
 377