openMSX
VDPVRAM.hh
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1 #ifndef VDPVRAM_HH
2 #define VDPVRAM_HH
3 
4 #include "VRAMObserver.hh"
5 #include "VDP.hh"
6 #include "VDPCmdEngine.hh"
7 #include "SimpleDebuggable.hh"
8 #include "Ram.hh"
9 #include "Math.hh"
10 #include "openmsx.hh"
11 #include "likely.hh"
12 #include <cassert>
13 
14 namespace openmsx {
15 
16 class DisplayMode;
17 class SpriteChecker;
18 class Renderer;
19 
20 /*
21 Note: The way VRAM is accessed depends a lot on who is doing the accessing.
22 
23 For example, the ranges:
24 - Table access is done using masks.
25 - Command engine work areas are rectangles.
26 - CPU access always spans full memory.
27 
28 Maybe define an interface with multiple subclasses?
29 Or is that too much of a performance hit?
30 If accessed through the interface, a virtual method call is made.
31 But invoking the objects directly should be inlined.
32 
33 Timing:
34 
35 Each window reflects the state of the VRAM at a specified moment in time.
36 
37 Because the CPU has full-range write access, it is incorrect for any window
38 to be ahead in time compared to the CPU. Because multi-cycle operations are
39 implemented as atomic, it is currently possible that a window which starts
40 an operation slightly before CPU time ends up slightly after CPU time.
41 Solutions:
42 - break up operations in 1-cycle suboperations
43  (very hard to reverse engineer accurately)
44 - do not start an operation until its end time is after CPU time
45  (requires minor rewrite of command engine)
46 - make the code that uses the timestamps resilient to after-CPU times
47  (current implementation; investigate if this is correct)
48 
49 Window ranges are not at fixed. But they can only be changed by the CPU, so
50 they are fixed until CPU time, which subsystems will never go beyond anyway.
51 
52 The only two subsystems with write access are CPU and command engine.
53 The command engine can only start executing a new command if instructed so
54 by the CPU. Therefore it is known which area the command engine can write
55 in until CPU time:
56 - empty, if the command engine is not executing a command
57 - the command's reach, if the command engine is executing a command
58 Currently the command's reach is not computed: full VRAM is used.
59 Taking the Y coordinate into account would speed things up a lot, because
60 usually commands execute on invisible pages, so the number of area overlaps
61 between renderer and command engine would be reduced significantly.
62 Also sprite tables are usually not written by commands.
63 
64 Reading through a window is done as follows:
65 A subsystem reads the VRAM because it is updating itself to a certain moment
66 in time T.
67 1. the subsystems syncs the window to T
68 2. VDPVRAM checks overlap of the window with the command write area
69  no overlap -> go to step 6
70 3. VDPVRAM syncs the command engine to T
71 4. the command engine calls VDPVRAM to write each byte it changes in VRAM,
72  call the times this happens C1, C2, C3...
73 5. at the n-th write, VDPVRAM updates any subsystem with the written address
74  in its window to Cn, this can include the original subsystem
75 6. the window has reached T
76  now the subsystem can update itself to T
77 Using this approach instead of syncing on read makes sure there is no
78 re-entrance on the subsystem update methods.
79 
80 Note: command engine reads through write window when doing logic-ops.
81 So "source window" and "destination window" would be better names.
82 
83 Interesting observation:
84 Each window is at the same moment in time as the command engine (C):
85 - if a window doesn't overlap with the command destination window, it is
86  stable from a moment before C until the CPU time T
87 - if a window overlaps with the command destination window, it cannot be
88  before C (incorrect) or after C (uncertainty)
89 Since there is only one time for the entire VRAM, the VRAM itself can be said
90 to be at C. This is a justification for having the sync method in VDPVRAM
91 instead of in Window.
92 
93 Writing through a window is done as follows:
94 - CPU write: sync with all non-CPU windows, including command engine write
95 - command engine write: sync with non-CPU and non-command engine windows
96 Syncing with a window is only necessary if the write falls into that window.
97 
98 If all non-CPU windows are disjunct, then all subsystems function
99 independently (at least until CPU time), no need for syncs.
100 So what is interesting, is which windows overlap.
101 Since windows change position infrequently, it may be beneficial to
102 precalculate overlaps.
103 Not necessarily though, because even if two windows overlap, a single write
104 may not be inside the other window. So precalculated overlaps only speeds up
105 in the case there is no overlap.
106 Maybe it's not necessary to know exactly which windows overlap with cmdwrite,
107 only to know whether there are any. If not, sync can be skipped.
108 
109 Is it possible to read multiple bytes at the same time?
110 In other words, get a pointer to an array instead of reading single bytes.
111 Yes, but only the first 64 bytes are guaranteed to be correct, because that
112 is the granularity of the color table.
113 But since whatever is reading the VRAM knows what it is operating on, it
114 can decide for itself how many bytes to read.
115 
116 */
117 
118 class DummyVRAMOBserver final : public VRAMObserver
119 {
120 public:
121  void updateVRAM(unsigned /*offset*/, EmuTime::param /*time*/) override {}
122  void updateWindow(bool /*enabled*/, EmuTime::param /*time*/) override {}
123 };
124 
136 {
137 public:
138  VRAMWindow(const VRAMWindow&) = delete;
139  VRAMWindow& operator=(const VRAMWindow&) = delete;
140 
146  [[nodiscard]] inline int getMask() const {
147  assert(isEnabled());
148  return effectiveBaseMask;
149  }
150 
163  inline void setMask(int newBaseMask, int newIndexMask,
164  EmuTime::param time) {
165  origBaseMask = newBaseMask;
166  newBaseMask &= sizeMask;
167  if (isEnabled() &&
168  (newBaseMask == effectiveBaseMask) &&
169  (newIndexMask == indexMask)) {
170  return;
171  }
172  observer->updateWindow(true, time);
173  effectiveBaseMask = newBaseMask;
174  indexMask = newIndexMask;
175  baseAddr = effectiveBaseMask & indexMask; // this enables window
176  combiMask = ~effectiveBaseMask | indexMask;
177  }
178 
182  inline void disable(EmuTime::param time) {
183  observer->updateWindow(false, time);
184  baseAddr = -1;
185  }
186 
190  [[nodiscard]] inline bool isContinuous(unsigned index, unsigned size) const {
191  assert(isEnabled());
192  unsigned endIndex = index + size - 1;
193  unsigned areaBits = Math::floodRight(index ^ endIndex);
194  if ((areaBits & effectiveBaseMask) != areaBits) return false;
195  if ((areaBits & ~indexMask) != areaBits) return false;
196  return true;
197  }
198 
207  [[nodiscard]] inline bool isContinuous(unsigned mask) const {
208  assert(isEnabled());
209  assert((mask & ~indexMask) == mask);
210  return (mask & effectiveBaseMask) == mask;
211  }
212 
219  [[nodiscard]] inline const byte* getReadArea(unsigned index, unsigned size) const {
220  assert(isContinuous(index, size)); (void)size;
221  return &data[effectiveBaseMask & (indexMask | index)];
222  }
223 
234  [[nodiscard]] inline std::pair<const byte*, const byte*> getReadAreaPlanar(
235  unsigned index, unsigned size) const {
236  assert((index & 1) == 0);
237  assert((size & 1) == 0);
238  unsigned endIndex = index + size - 1;
239  unsigned areaBits = Math::floodRight(index ^ endIndex);
240  areaBits = ((areaBits << 16) | (areaBits >> 1)) & 0x1FFFF & sizeMask;
241  (void)areaBits;
242  assert((areaBits & effectiveBaseMask) == areaBits);
243  assert((areaBits & ~indexMask) == areaBits);
244  assert(isEnabled());
245  unsigned addr = effectiveBaseMask & (indexMask | (index >> 1));
246  const byte* ptr0 = &data[addr | 0x00000];
247  const byte* ptr1 = &data[addr | 0x10000];
248  return {ptr0, ptr1};
249  }
250 
254  [[nodiscard]] inline byte readNP(unsigned index) const {
255  assert(isEnabled());
256  return data[effectiveBaseMask & index];
257  }
258 
262  [[nodiscard]] inline byte readPlanar(unsigned index) const {
263  assert(isEnabled());
264  index = ((index & 1) << 16) | ((index & 0x1FFFE) >> 1);
265  unsigned addr = effectiveBaseMask & index;
266  return data[addr];
267  }
268 
271  [[nodiscard]] inline bool hasObserver() const {
272  return observer != &dummyObserver;
273  }
274 
280  inline void setObserver(VRAMObserver* newObserver) {
281  observer = newObserver;
282  }
283 
286  inline void resetObserver() {
287  observer = &dummyObserver;
288  }
289 
297  [[nodiscard]] inline bool isInside(unsigned address) const {
298  return (address & combiMask) == unsigned(baseAddr);
299  }
300 
306  inline void notify(unsigned address, EmuTime::param time) {
307  if (isInside(address)) {
308  observer->updateVRAM(address - baseAddr, time);
309  }
310  }
311 
316  void setSizeMask(unsigned newSizeMask, EmuTime::param time) {
317  sizeMask = newSizeMask;
318  if (isEnabled()) {
319  setMask(origBaseMask, indexMask, time);
320  }
321  }
322 
323  template<typename Archive>
324  void serialize(Archive& ar, unsigned version);
325 
326 private:
327  [[nodiscard]] inline bool isEnabled() const {
328  return baseAddr != -1;
329  }
330 
331 private:
334  friend class VDPVRAM;
335 
339  explicit VRAMWindow(Ram& vram);
340 
343  byte* data;
344 
349  VRAMObserver* observer;
350 
353  int origBaseMask;
354 
358  int effectiveBaseMask;
359 
362  int indexMask;
363 
367  int baseAddr;
368 
371  int combiMask;
372 
377  int sizeMask;
378 
379  static inline DummyVRAMOBserver dummyObserver;
380 };
381 
386 class VDPVRAM
387 {
388 public:
389  VDPVRAM(const VDPVRAM&) = delete;
390  VDPVRAM& operator=(const VDPVRAM&) = delete;
391 
392  VDPVRAM(VDP& vdp, unsigned size, EmuTime::param time);
393 
396  void clear();
397 
402  inline void sync(EmuTime::param time) {
403  assert(vdp.isInsideFrame(time));
404  cmdEngine->sync(time);
405  }
406 
413  inline void cmdWrite(unsigned address, byte value, EmuTime::param time) {
414  #ifdef DEBUG
415  // Rewriting history is not allowed.
416  assert(time >= vramTime);
417  #endif
418  assert(vdp.isInsideFrame(time));
419 
420  // handle mirroring and non-present ram chips
421  address &= sizeMask;
422  if (unlikely(address >= actualSize)) {
423  // 192kb vram is mirroring is handled elsewhere
424  assert(address < 0x30000);
425  // only happens in case of 16kb vram while you write
426  // to range [0x4000,0x8000)
427  return;
428  }
429 
430  writeCommon(address, value, time);
431  }
432 
438  inline void cpuWrite(unsigned address, byte value, EmuTime::param time) {
439  #ifdef DEBUG
440  // Rewriting history is not allowed.
441  assert(time >= vramTime);
442  #endif
443  assert(vdp.isInsideFrame(time));
444 
445  // handle mirroring and non-present ram chips
446  address &= sizeMask;
447  if (unlikely(address >= actualSize)) {
448  // 192kb vram is mirroring is handled elsewhere
449  assert(address < 0x30000);
450  // only happens in case of 16kb vram while you write
451  // to range [0x4000,0x8000)
452  return;
453  }
454 
455  // We should still sync with cmdEngine, even if the VRAM already
456  // contains the value we're about to write (e.g. it's possible
457  // syncing with cmdEngine changes that value, and this write
458  // restores it again). This fixes bug:
459  // [2844043] Hinotori - Firebird small graphics corruption
460  if (cmdReadWindow .isInside(address) ||
461  cmdWriteWindow.isInside(address)) {
462  cmdEngine->sync(time);
463  }
464  writeCommon(address, value, time);
465 
466  cmdEngine->stealAccessSlot(time);
467  }
468 
474  [[nodiscard]] inline byte cpuRead(unsigned address, EmuTime::param time) {
475  #ifdef DEBUG
476  // VRAM should never get ahead of CPU.
477  assert(time >= vramTime);
478  #endif
479  assert(vdp.isInsideFrame(time));
480 
481  address &= sizeMask;
482  if (cmdWriteWindow.isInside(address)) {
483  cmdEngine->sync(time);
484  }
485  cmdEngine->stealAccessSlot(time);
486 
487  #ifdef DEBUG
488  vramTime = time;
489  #endif
490  return data[address];
491  }
492 
501  void updateDisplayMode(DisplayMode mode, bool cmdBit, EmuTime::param time);
502 
509  void updateDisplayEnabled(bool enabled, EmuTime::param time);
510 
515  void updateSpritesEnabled(bool enabled, EmuTime::param time);
516 
521  void updateVRMode(bool mode, EmuTime::param time);
522 
523  void setRenderer(Renderer* renderer, EmuTime::param time);
524 
527  [[nodiscard]] unsigned getSize() const {
528  return actualSize;
529  }
530 
533  inline void setSpriteChecker(SpriteChecker* newSpriteChecker) {
534  spriteChecker = newSpriteChecker;
535  }
536 
539  inline void setCmdEngine(VDPCmdEngine* newCmdEngine) {
540  cmdEngine = newCmdEngine;
541  }
542 
546  void change4k8kMapping(bool mapping8k);
547 
548  template<typename Archive>
549  void serialize(Archive& ar, unsigned version);
550 
551 private:
552  /* Common code of cmdWrite() and cpuWrite()
553  */
554  inline void writeCommon(unsigned address, byte value, EmuTime::param time) {
555  #ifdef DEBUG
556  assert(time >= vramTime);
557  vramTime = time;
558  #endif
559 
560  // Check that VRAM will actually be changed.
561  // A lot of costly syncs can be saved if the same value is written.
562  // For example Penguin Adventure always uploads the whole frame,
563  // even if it is the same as the previous frame.
564  if (data[address] == value) return;
565 
566  // Subsystem synchronisation should happen before the commit,
567  // to be able to draw backlog using old state.
568  bitmapVisibleWindow.notify(address, time);
569  spriteAttribTable.notify(address, time);
570  spritePatternTable.notify(address, time);
571 
572  data[address] = value;
573 
574  // Cache dirty marking should happen after the commit,
575  // otherwise the cache could be re-validated based on old state.
576 
577  // these two seem to be unused
578  // bitmapCacheWindow.notify(address, time);
579  // nameTable.notify(address, time);
580  assert(!bitmapCacheWindow.hasObserver());
581  assert(!nameTable.hasObserver());
582 
583  // in the past GLRasterizer observed these two, now there are none
584  assert(!colorTable.hasObserver());
585  assert(!patternTable.hasObserver());
586 
587  /* TODO:
588  There seems to be a significant difference between subsystem sync
589  and cache admin. One example is the code above, the other is
590  updateWindow, where subsystem sync is interested in windows that
591  were enabled before (new state doesn't matter), while cache admin
592  is interested in windows that become enabled (old state doesn't
593  matter).
594  Does this mean it makes sense to have separate VRAMWindow like
595  classes for each category?
596  Note: In the future, sprites may switch category, or fall in both.
597  */
598  }
599 
600  void setSizeMask(EmuTime::param time);
601 
602 private:
605  VDP& vdp;
606 
609  Ram data;
610 
616  class LogicalVRAMDebuggable final : public SimpleDebuggable {
617  public:
618  explicit LogicalVRAMDebuggable(VDP& vdp);
619  [[nodiscard]] byte read(unsigned address, EmuTime::param time) override;
620  void write(unsigned address, byte value, EmuTime::param time) override;
621  private:
622  unsigned transform(unsigned address);
623  } logicalVRAMDebug;
624 
629  struct PhysicalVRAMDebuggable final : SimpleDebuggable {
630  PhysicalVRAMDebuggable(VDP& vdp, unsigned actualSize);
631  [[nodiscard]] byte read(unsigned address, EmuTime::param time) override;
632  void write(unsigned address, byte value, EmuTime::param time) override;
633  } physicalVRAMDebug;
634 
635  // TODO: Renderer field can be removed, if updateDisplayMode
636  // and updateDisplayEnabled are moved back to VDP.
637  // Is that a good idea?
638  Renderer* renderer;
639 
640  VDPCmdEngine* cmdEngine;
641  SpriteChecker* spriteChecker;
642 
647  #ifdef DEBUG
648  EmuTime vramTime;
649  #endif
650 
655  unsigned sizeMask;
656 
660  const unsigned actualSize;
661 
664  bool vrMode;
665 
666 public:
676 };
677 
678 } // namespace openmsx
679 
680 #endif
Represents a VDP display mode.
Definition: DisplayMode.hh:16
void updateVRAM(unsigned, EmuTime::param) override
Informs the observer of a change in VRAM contents.
Definition: VDPVRAM.hh:121
void updateWindow(bool, EmuTime::param) override
Informs the observer that the entire VRAM window will change.
Definition: VDPVRAM.hh:122
Abstract base class for Renderers.
Definition: Renderer.hh:23
byte read(unsigned address) override
void write(unsigned address, byte value) override
VDP command engine by Alex Wulms.
Definition: VDPCmdEngine.hh:23
void stealAccessSlot(EmuTime::param time)
Steal a VRAM access slot from the CmdEngine.
Definition: VDPCmdEngine.hh:46
void sync(EmuTime::param time)
Synchronizes the command engine with the VDP.
Definition: VDPCmdEngine.hh:37
Manages VRAM contents and synchronizes the various users of the VRAM.
Definition: VDPVRAM.hh:387
void updateSpritesEnabled(bool enabled, EmuTime::param time)
Used by the VDP to signal sprites enabled changes.
Definition: VDPVRAM.cc:167
VRAMWindow spriteAttribTable
Definition: VDPVRAM.hh:674
void clear()
Initialize VRAM content to power-up state.
Definition: VDPVRAM.cc:138
VDPVRAM(const VDPVRAM &)=delete
void cmdWrite(unsigned address, byte value, EmuTime::param time)
Write a byte from the command engine.
Definition: VDPVRAM.hh:413
void setRenderer(Renderer *renderer, EmuTime::param time)
Definition: VDPVRAM.cc:226
VRAMWindow colorTable
Definition: VDPVRAM.hh:670
void updateVRMode(bool mode, EmuTime::param time)
Change between VR=0 and VR=1 mode.
Definition: VDPVRAM.cc:203
VRAMWindow cmdReadWindow
Definition: VDPVRAM.hh:667
VRAMWindow bitmapCacheWindow
Definition: VDPVRAM.hh:673
void updateDisplayEnabled(bool enabled, EmuTime::param time)
Used by the VDP to signal display enabled changes.
Definition: VDPVRAM.cc:159
void setSpriteChecker(SpriteChecker *newSpriteChecker)
Necessary because of circular dependencies.
Definition: VDPVRAM.hh:533
void updateDisplayMode(DisplayMode mode, bool cmdBit, EmuTime::param time)
Used by the VDP to signal display mode changes.
Definition: VDPVRAM.cc:151
VRAMWindow bitmapVisibleWindow
Definition: VDPVRAM.hh:672
void sync(EmuTime::param time)
Update VRAM state to specified moment in time.
Definition: VDPVRAM.hh:402
byte cpuRead(unsigned address, EmuTime::param time)
Read a byte from VRAM though the CPU interface.
Definition: VDPVRAM.hh:474
void serialize(Archive &ar, unsigned version)
Definition: VDPVRAM.cc:323
unsigned getSize() const
Returns the size of VRAM in bytes.
Definition: VDPVRAM.hh:527
VRAMWindow spritePatternTable
Definition: VDPVRAM.hh:675
void cpuWrite(unsigned address, byte value, EmuTime::param time)
Write a byte to VRAM through the CPU interface.
Definition: VDPVRAM.hh:438
VRAMWindow patternTable
Definition: VDPVRAM.hh:671
VRAMWindow cmdWriteWindow
Definition: VDPVRAM.hh:668
void setCmdEngine(VDPCmdEngine *newCmdEngine)
Necessary because of circular dependencies.
Definition: VDPVRAM.hh:539
void change4k8kMapping(bool mapping8k)
TMS99x8 VRAM can be mapped in two ways.
Definition: VDPVRAM.cc:239
VRAMWindow nameTable
Definition: VDPVRAM.hh:669
VDPVRAM & operator=(const VDPVRAM &)=delete
Unified implementation of MSX Video Display Processors (VDPs).
Definition: VDP.hh:63
bool isInsideFrame(EmuTime::param time) const
Is the given timestamp inside the current frame? Mainly useful for debugging, because relevant timest...
Definition: VDP.hh:514
Interface that can be registered at VRAMWindow, to be called when the contents of the VRAM inside tha...
Definition: VRAMObserver.hh:11
virtual void updateVRAM(unsigned offset, EmuTime::param time)=0
Informs the observer of a change in VRAM contents.
virtual void updateWindow(bool enabled, EmuTime::param time)=0
Informs the observer that the entire VRAM window will change.
Specifies an address range in the VRAM.
Definition: VDPVRAM.hh:136
void disable(EmuTime::param time)
Disable this window: no address will be considered inside.
Definition: VDPVRAM.hh:182
VRAMWindow & operator=(const VRAMWindow &)=delete
bool isContinuous(unsigned index, unsigned size) const
Is the given index range continuous in VRAM (iow there's no mirroring) Only if the range is continuou...
Definition: VDPVRAM.hh:190
int getMask() const
Gets the mask for this window.
Definition: VDPVRAM.hh:146
void notify(unsigned address, EmuTime::param time)
Notifies the observer of this window of a VRAM change, if the changes address is inside this window.
Definition: VDPVRAM.hh:306
byte readNP(unsigned index) const
Reads a byte from VRAM in its current state.
Definition: VDPVRAM.hh:254
bool hasObserver() const
Is there an observer registered for this window?
Definition: VDPVRAM.hh:271
bool isInside(unsigned address) const
Test whether an address is inside this window.
Definition: VDPVRAM.hh:297
void serialize(Archive &ar, unsigned version)
Definition: VDPVRAM.cc:310
bool isContinuous(unsigned mask) const
Alternative version to check whether a region is continuous in VRAM.
Definition: VDPVRAM.hh:207
void setSizeMask(unsigned newSizeMask, EmuTime::param time)
Inform VRAMWindow of changed sizeMask.
Definition: VDPVRAM.hh:316
byte readPlanar(unsigned index) const
Similar to readNP, but now with planar addressing.
Definition: VDPVRAM.hh:262
const byte * getReadArea(unsigned index, unsigned size) const
Gets a pointer to a contiguous part of the VRAM.
Definition: VDPVRAM.hh:219
VRAMWindow(const VRAMWindow &)=delete
void setMask(int newBaseMask, int newIndexMask, EmuTime::param time)
Sets the mask and enables this window.
Definition: VDPVRAM.hh:163
void setObserver(VRAMObserver *newObserver)
Register an observer on this VRAM window.
Definition: VDPVRAM.hh:280
std::pair< const byte *, const byte * > getReadAreaPlanar(unsigned index, unsigned size) const
Similar to getReadArea(), but now with planar addressing mode.
Definition: VDPVRAM.hh:234
void resetObserver()
Unregister the observer of this VRAM window.
Definition: VDPVRAM.hh:286
#define unlikely(x)
Definition: likely.hh:15
constexpr T floodRight(T x) noexcept
Returns the smallest number of the form 2^n-1 that is greater or equal to the given number.
Definition: Math.hh:69
This file implemented 3 utility functions:
Definition: Autofire.cc:9
Ram
Definition: Ram.cc:125
constexpr nibble mask[4][13]
Definition: RP5C01.cc:34
auto transform(InputRange &&range, OutputIter out, UnaryOperation op)
Definition: ranges.hh:190
size_t size(std::string_view utf8)