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 <cassert>
12
13namespace openmsx {
14
15class DisplayMode;
16class SpriteChecker;
17class Renderer;
18
19/*
20Note: The way VRAM is accessed depends a lot on who is doing the accessing.
21
22For example, the ranges:
23- Table access is done using masks.
24- Command engine work areas are rectangles.
25- CPU access always spans full memory.
26
27Maybe define an interface with multiple subclasses?
28Or is that too much of a performance hit?
29If accessed through the interface, a virtual method call is made.
30But invoking the objects directly should be inlined.
31
32Timing:
33
34Each window reflects the state of the VRAM at a specified moment in time.
35
36Because the CPU has full-range write access, it is incorrect for any window
37to be ahead in time compared to the CPU. Because multi-cycle operations are
38implemented as atomic, it is currently possible that a window which starts
39an operation slightly before CPU time ends up slightly after CPU time.
40Solutions:
41- break up operations in 1-cycle suboperations
42 (very hard to reverse engineer accurately)
43- do not start an operation until its end time is after CPU time
44 (requires minor rewrite of command engine)
45- make the code that uses the timestamps resilient to after-CPU times
46 (current implementation; investigate if this is correct)
47
48Window ranges are not at fixed. But they can only be changed by the CPU, so
49they are fixed until CPU time, which subsystems will never go beyond anyway.
50
51The only two subsystems with write access are CPU and command engine.
52The command engine can only start executing a new command if instructed so
53by the CPU. Therefore it is known which area the command engine can write
54in until CPU time:
55- empty, if the command engine is not executing a command
56- the command's reach, if the command engine is executing a command
57Currently the command's reach is not computed: full VRAM is used.
58Taking the Y coordinate into account would speed things up a lot, because
59usually commands execute on invisible pages, so the number of area overlaps
60between renderer and command engine would be reduced significantly.
61Also sprite tables are usually not written by commands.
62
63Reading through a window is done as follows:
64A subsystem reads the VRAM because it is updating itself to a certain moment
65in time T.
661. the subsystems syncs the window to T
672. VDPVRAM checks overlap of the window with the command write area
68 no overlap -> go to step 6
693. VDPVRAM syncs the command engine to T
704. the command engine calls VDPVRAM to write each byte it changes in VRAM,
71 call the times this happens C1, C2, C3...
725. at the n-th write, VDPVRAM updates any subsystem with the written address
73 in its window to Cn, this can include the original subsystem
746. the window has reached T
75 now the subsystem can update itself to T
76Using this approach instead of syncing on read makes sure there is no
77re-entrance on the subsystem update methods.
78
79Note: command engine reads through write window when doing logic-ops.
80So "source window" and "destination window" would be better names.
81
82Interesting observation:
83Each window is at the same moment in time as the command engine (C):
84- if a window doesn't overlap with the command destination window, it is
85 stable from a moment before C until the CPU time T
86- if a window overlaps with the command destination window, it cannot be
87 before C (incorrect) or after C (uncertainty)
88Since there is only one time for the entire VRAM, the VRAM itself can be said
89to be at C. This is a justification for having the sync method in VDPVRAM
90instead of in Window.
91
92Writing through a window is done as follows:
93- CPU write: sync with all non-CPU windows, including command engine write
94- command engine write: sync with non-CPU and non-command engine windows
95Syncing with a window is only necessary if the write falls into that window.
96
97If all non-CPU windows are disjunct, then all subsystems function
98independently (at least until CPU time), no need for syncs.
99So what is interesting, is which windows overlap.
100Since windows change position infrequently, it may be beneficial to
101precalculate overlaps.
102Not necessarily though, because even if two windows overlap, a single write
103may not be inside the other window. So precalculated overlaps only speeds up
104in the case there is no overlap.
105Maybe it's not necessary to know exactly which windows overlap with cmdWrite,
106only to know whether there are any. If not, sync can be skipped.
107
108Is it possible to read multiple bytes at the same time?
109In other words, get a pointer to an array instead of reading single bytes.
110Yes, but only the first 64 bytes are guaranteed to be correct, because that
111is the granularity of the color table.
112But since whatever is reading the VRAM knows what it is operating on, it
113can decide for itself how many bytes to read.
114
115*/
116
117class DummyVRAMObserver final : public VRAMObserver
118{
119public:
120 void updateVRAM(unsigned /*offset*/, EmuTime::param /*time*/) override {}
121 void updateWindow(bool /*enabled*/, EmuTime::param /*time*/) override {}
122};
123
135{
136public:
137 VRAMWindow(const VRAMWindow&) = delete;
138 VRAMWindow& operator=(const VRAMWindow&) = delete;
139
145 [[nodiscard]] inline unsigned getMask() const {
146 assert(isEnabled());
147 return effectiveBaseMask;
148 }
149
163 inline void setMask(unsigned newBaseMask, unsigned newIndexMask,
164 unsigned newSizeMask, EmuTime::param time) {
165 origBaseMask = newBaseMask;
166 newBaseMask &= newSizeMask;
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 setMask(unsigned newBaseMask, unsigned newIndexMask,
183 EmuTime::param time) {
184 setMask(newBaseMask, newIndexMask, sizeMask, time);
185 }
186
190 inline void disable(EmuTime::param time) {
191 observer->updateWindow(false, time);
192 baseAddr = unsigned(-1);
193 }
194
198 [[nodiscard]] inline bool isContinuous(unsigned index, unsigned size) const {
199 assert(isEnabled());
200 unsigned endIndex = index + size - 1;
201 unsigned areaBits = Math::floodRight(index ^ endIndex);
202 if ((areaBits & effectiveBaseMask) != areaBits) return false;
203 if ((areaBits & ~indexMask) != areaBits) return false;
204 return true;
205 }
206
215 [[nodiscard]] inline bool isContinuous(unsigned mask) const {
216 assert(isEnabled());
217 assert((mask & ~indexMask) == mask);
218 return (mask & effectiveBaseMask) == mask;
219 }
220
225 template<size_t size>
226 [[nodiscard]] inline std::span<const byte, size> getReadArea(unsigned index) const {
227 assert(isContinuous(index, size));
228 return std::span<const byte, size>{
229 &data[effectiveBaseMask & (indexMask | index)],
230 size};
231 }
232
241 template<size_t size>
242 [[nodiscard]] inline std::pair<std::span<const byte, size / 2>, std::span<const byte, size / 2>>
243 getReadAreaPlanar(unsigned index) const {
244 assert((index & 1) == 0);
245 assert((size & 1) == 0);
246 unsigned endIndex = index + size - 1;
247 unsigned areaBits = Math::floodRight(index ^ endIndex);
248 areaBits = ((areaBits << 16) | (areaBits >> 1)) & 0x1FFFF & sizeMask;
249 (void)areaBits;
250 assert((areaBits & effectiveBaseMask) == areaBits);
251 assert((areaBits & ~indexMask) == areaBits);
252 assert(isEnabled());
253 unsigned addr = effectiveBaseMask & (indexMask | (index >> 1));
254 const byte* ptr0 = &data[addr | 0x00000];
255 const byte* ptr1 = &data[addr | 0x10000];
256 return {std::span<const byte, size / 2>{ptr0, size / 2},
257 std::span<const byte, size / 2>{ptr1, size / 2}};
258 }
259
263 [[nodiscard]] inline byte readNP(unsigned index) const {
264 assert(isEnabled());
265 return data[effectiveBaseMask & index];
266 }
267
271 [[nodiscard]] inline byte readPlanar(unsigned index) const {
272 assert(isEnabled());
273 index = ((index & 1) << 16) | ((index & 0x1FFFE) >> 1);
274 unsigned addr = effectiveBaseMask & index;
275 return data[addr];
276 }
277
280 [[nodiscard]] inline bool hasObserver() const {
281 return observer != &dummyObserver;
282 }
283
289 inline void setObserver(VRAMObserver* newObserver) {
290 observer = newObserver;
291 }
292
295 inline void resetObserver() {
296 observer = &dummyObserver;
297 }
298
306 [[nodiscard]] inline bool isInside(unsigned address) const {
307 return (address & combiMask) == baseAddr;
308 }
309
315 inline void notify(unsigned address, EmuTime::param time) {
316 if (isInside(address)) {
317 observer->updateVRAM(address - baseAddr, time);
318 }
319 }
320
325 void setSizeMask(unsigned newSizeMask, EmuTime::param time) {
326 if (isEnabled()) {
327 setMask(origBaseMask, indexMask, newSizeMask, time);
328 }
329 // only apply sizeMask after observers have been notified
330 sizeMask = newSizeMask;
331 }
332
333 template<typename Archive>
334 void serialize(Archive& ar, unsigned version);
335
336private:
337 [[nodiscard]] inline bool isEnabled() const {
338 return baseAddr != unsigned(-1);
339 }
340
341private:
344 friend class VDPVRAM;
345
349 explicit VRAMWindow(Ram& vram);
350
353 byte* data;
354
359 VRAMObserver* observer = &dummyObserver;
360
363 unsigned origBaseMask = 0;
364
368 unsigned effectiveBaseMask = 0;
369
372 unsigned indexMask = 0;
373
377 unsigned baseAddr = unsigned(-1); // disable window
378
381 unsigned combiMask = 0;
382
387 unsigned sizeMask;
388
389 static inline DummyVRAMObserver dummyObserver;
390};
391
397{
398public:
399 VDPVRAM(const VDPVRAM&) = delete;
400 VDPVRAM& operator=(const VDPVRAM&) = delete;
401
402 VDPVRAM(VDP& vdp, unsigned size, EmuTime::param time);
403
406 void clear();
407
412 inline void sync(EmuTime::param time) {
413 assert(vdp.isInsideFrame(time));
414 cmdEngine->sync(time);
415 }
416
423 inline void cmdWrite(unsigned address, byte value, EmuTime::param time) {
424 #ifdef DEBUG
425 // Rewriting history is not allowed.
426 assert(time >= vramTime);
427 #endif
428 assert(vdp.isInsideFrame(time));
429
430 // handle mirroring and non-present ram chips
431 address &= sizeMask;
432 if (address >= actualSize) [[unlikely]] {
433 // 192kb vram is mirroring is handled elsewhere
434 assert(address < 0x30000);
435 // only happens in case of 16kb vram while you write
436 // to range [0x4000,0x8000)
437 return;
438 }
439
440 writeCommon(address, value, time);
441 }
442
448 inline void cpuWrite(unsigned address, byte value, EmuTime::param time) {
449 #ifdef DEBUG
450 // Rewriting history is not allowed.
451 assert(time >= vramTime);
452 #endif
453 assert(vdp.isInsideFrame(time));
454
455 // handle mirroring and non-present ram chips
456 address &= sizeMask;
457 if (address >= actualSize) [[unlikely]] {
458 // 192kb vram is mirroring is handled elsewhere
459 assert(address < 0x30000);
460 // only happens in case of 16kb vram while you write
461 // to range [0x4000,0x8000)
462 return;
463 }
464
465 // We should still sync with cmdEngine, even if the VRAM already
466 // contains the value we're about to write (e.g. it's possible
467 // syncing with cmdEngine changes that value, and this write
468 // restores it again). This fixes bug:
469 // [2844043] Hinotori - Firebird small graphics corruption
470 if (cmdReadWindow .isInside(address) ||
471 cmdWriteWindow.isInside(address)) {
472 cmdEngine->sync(time);
473 }
474 writeCommon(address, value, time);
475
476 cmdEngine->stealAccessSlot(time);
477 }
478
484 [[nodiscard]] inline byte cpuRead(unsigned address, EmuTime::param time) {
485 #ifdef DEBUG
486 // VRAM should never get ahead of CPU.
487 assert(time >= vramTime);
488 #endif
489 assert(vdp.isInsideFrame(time));
490
491 address &= sizeMask;
492 if (cmdWriteWindow.isInside(address)) {
493 cmdEngine->sync(time);
494 }
495 cmdEngine->stealAccessSlot(time);
496
497 #ifdef DEBUG
498 vramTime = time;
499 #endif
500 return data[address];
501 }
502
511 void updateDisplayMode(DisplayMode mode, bool cmdBit, EmuTime::param time);
512
519 void updateDisplayEnabled(bool enabled, EmuTime::param time);
520
525 void updateSpritesEnabled(bool enabled, EmuTime::param time);
526
531 void updateVRMode(bool mode, EmuTime::param time);
532
533 void setRenderer(Renderer* renderer, EmuTime::param time);
534
537 [[nodiscard]] unsigned getSize() const {
538 return actualSize;
539 }
540
543 inline void setSpriteChecker(SpriteChecker* newSpriteChecker) {
544 spriteChecker = newSpriteChecker;
545 }
546
549 inline void setCmdEngine(VDPCmdEngine* newCmdEngine) {
550 cmdEngine = newCmdEngine;
551 }
552
556 void change4k8kMapping(bool mapping8k);
557
560 [[nodiscard]] std::span<const uint8_t> getData() const {
561 return {data.data(), data.size()};
562 }
563
564 template<typename Archive>
565 void serialize(Archive& ar, unsigned version);
566
567private:
568 /* Common code of cmdWrite() and cpuWrite()
569 */
570 inline void writeCommon(unsigned address, byte value, EmuTime::param time) {
571 #ifdef DEBUG
572 assert(time >= vramTime);
573 vramTime = time;
574 #endif
575
576 // Check that VRAM will actually be changed.
577 // A lot of costly syncs can be saved if the same value is written.
578 // For example Penguin Adventure always uploads the whole frame,
579 // even if it is the same as the previous frame.
580 if (data[address] == value) return;
581
582 // Subsystem synchronisation should happen before the commit,
583 // to be able to draw backlog using old state.
584 bitmapVisibleWindow.notify(address, time);
585 spriteAttribTable.notify(address, time);
586 spritePatternTable.notify(address, time);
587
588 data[address] = value;
589
590 // Cache dirty marking should happen after the commit,
591 // otherwise the cache could be re-validated based on old state.
592
593 // these two seem to be unused
594 // bitmapCacheWindow.notify(address, time);
595 // nameTable.notify(address, time);
597 assert(!nameTable.hasObserver());
598
599 // in the past GLRasterizer observed these two, now there are none
600 assert(!colorTable.hasObserver());
601 assert(!patternTable.hasObserver());
602
603 /* TODO:
604 There seems to be a significant difference between subsystem sync
605 and cache admin. One example is the code above, the other is
606 updateWindow, where subsystem sync is interested in windows that
607 were enabled before (new state doesn't matter), while cache admin
608 is interested in windows that become enabled (old state doesn't
609 matter).
610 Does this mean it makes sense to have separate VRAMWindow like
611 classes for each category?
612 Note: In the future, sprites may switch category, or fall in both.
613 */
614 }
615
616 void setSizeMask(EmuTime::param time);
617
618private:
621 VDP& vdp;
622
625 Ram data;
626
632 class LogicalVRAMDebuggable final : public SimpleDebuggable {
633 public:
634 explicit LogicalVRAMDebuggable(VDP& vdp);
635 [[nodiscard]] byte read(unsigned address, EmuTime::param time) override;
636 void write(unsigned address, byte value, EmuTime::param time) override;
637 private:
638 unsigned transform(unsigned address);
639 } logicalVRAMDebug;
640
645 struct PhysicalVRAMDebuggable final : SimpleDebuggable {
646 PhysicalVRAMDebuggable(VDP& vdp, unsigned actualSize);
647 [[nodiscard]] byte read(unsigned address, EmuTime::param time) override;
648 void write(unsigned address, byte value, EmuTime::param time) override;
649 } physicalVRAMDebug;
650
651 // TODO: Renderer field can be removed, if updateDisplayMode
652 // and updateDisplayEnabled are moved back to VDP.
653 // Is that a good idea?
654 Renderer* renderer;
655
656 VDPCmdEngine* cmdEngine;
657 SpriteChecker* spriteChecker;
658
663 #ifdef DEBUG
664 EmuTime vramTime;
665 #endif
666
671 unsigned sizeMask;
672
676 const unsigned actualSize;
677
680 bool vrMode;
681
682public:
692};
693
694} // namespace openmsx
695
696#endif
Represents a VDP display mode.
void updateVRAM(unsigned, EmuTime::param) override
Informs the observer of a change in VRAM contents.
Definition VDPVRAM.hh:120
void updateWindow(bool, EmuTime::param) override
Informs the observer that the entire VRAM window will change.
Definition VDPVRAM.hh:121
auto size() const
Definition Ram.hh:44
auto data()
Definition Ram.hh:45
Abstract base class for Renderers.
Definition Renderer.hh:24
byte read(unsigned address) override
void write(unsigned address, byte value) override
VDP command engine by Alex Wulms.
void stealAccessSlot(EmuTime::param time)
Steal a VRAM access slot from the CmdEngine.
void sync(EmuTime::param time)
Synchronizes the command engine with the VDP.
Manages VRAM contents and synchronizes the various users of the VRAM.
Definition VDPVRAM.hh:397
void updateSpritesEnabled(bool enabled, EmuTime::param time)
Used by the VDP to signal sprites enabled changes.
Definition VDPVRAM.cc:160
VRAMWindow spriteAttribTable
Definition VDPVRAM.hh:690
void clear()
Initialize VRAM content to power-up state.
Definition VDPVRAM.cc:131
VDPVRAM(const VDPVRAM &)=delete
void cmdWrite(unsigned address, byte value, EmuTime::param time)
Write a byte from the command engine.
Definition VDPVRAM.hh:423
VDPVRAM & operator=(const VDPVRAM &)=delete
void setRenderer(Renderer *renderer, EmuTime::param time)
Definition VDPVRAM.cc:221
VRAMWindow colorTable
Definition VDPVRAM.hh:686
void updateVRMode(bool mode, EmuTime::param time)
Change between VR=0 and VR=1 mode.
Definition VDPVRAM.cc:198
VRAMWindow cmdReadWindow
Definition VDPVRAM.hh:683
VRAMWindow bitmapCacheWindow
Definition VDPVRAM.hh:689
void updateDisplayEnabled(bool enabled, EmuTime::param time)
Used by the VDP to signal display enabled changes.
Definition VDPVRAM.cc:152
void setSpriteChecker(SpriteChecker *newSpriteChecker)
Necessary because of circular dependencies.
Definition VDPVRAM.hh:543
void updateDisplayMode(DisplayMode mode, bool cmdBit, EmuTime::param time)
Used by the VDP to signal display mode changes.
Definition VDPVRAM.cc:144
VRAMWindow bitmapVisibleWindow
Definition VDPVRAM.hh:688
void sync(EmuTime::param time)
Update VRAM state to specified moment in time.
Definition VDPVRAM.hh:412
byte cpuRead(unsigned address, EmuTime::param time)
Read a byte from VRAM though the CPU interface.
Definition VDPVRAM.hh:484
void serialize(Archive &ar, unsigned version)
Definition VDPVRAM.cc:317
unsigned getSize() const
Returns the size of VRAM in bytes.
Definition VDPVRAM.hh:537
std::span< const uint8_t > getData() const
Only used by debugger.
Definition VDPVRAM.hh:560
VRAMWindow spritePatternTable
Definition VDPVRAM.hh:691
void cpuWrite(unsigned address, byte value, EmuTime::param time)
Write a byte to VRAM through the CPU interface.
Definition VDPVRAM.hh:448
VRAMWindow patternTable
Definition VDPVRAM.hh:687
VRAMWindow cmdWriteWindow
Definition VDPVRAM.hh:684
void setCmdEngine(VDPCmdEngine *newCmdEngine)
Necessary because of circular dependencies.
Definition VDPVRAM.hh:549
void change4k8kMapping(bool mapping8k)
TMS99x8 VRAM can be mapped in two ways.
Definition VDPVRAM.cc:234
VRAMWindow nameTable
Definition VDPVRAM.hh:685
Unified implementation of MSX Video Display Processors (VDPs).
Definition VDP.hh:64
bool isInsideFrame(EmuTime::param time) const
Is the given timestamp inside the current frame? Mainly useful for debugging, because relevant timest...
Definition VDP.hh:576
Interface that can be registered at VRAMWindow, to be called when the contents of the VRAM inside tha...
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:135
void setMask(unsigned newBaseMask, unsigned newIndexMask, unsigned newSizeMask, EmuTime::param time)
Sets the mask and enables this window.
Definition VDPVRAM.hh:163
void disable(EmuTime::param time)
Disable this window: no address will be considered inside.
Definition VDPVRAM.hh:190
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:198
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:315
byte readNP(unsigned index) const
Reads a byte from VRAM in its current state.
Definition VDPVRAM.hh:263
bool hasObserver() const
Is there an observer registered for this window?
Definition VDPVRAM.hh:280
VRAMWindow & operator=(const VRAMWindow &)=delete
bool isInside(unsigned address) const
Test whether an address is inside this window.
Definition VDPVRAM.hh:306
void serialize(Archive &ar, unsigned version)
Definition VDPVRAM.cc:304
void setMask(unsigned newBaseMask, unsigned newIndexMask, EmuTime::param time)
Same as above, but 'sizeMask' doesn't change.
Definition VDPVRAM.hh:182
bool isContinuous(unsigned mask) const
Alternative version to check whether a region is continuous in VRAM.
Definition VDPVRAM.hh:215
void setSizeMask(unsigned newSizeMask, EmuTime::param time)
Inform VRAMWindow of changed sizeMask.
Definition VDPVRAM.hh:325
byte readPlanar(unsigned index) const
Similar to readNP, but now with planar addressing.
Definition VDPVRAM.hh:271
VRAMWindow(const VRAMWindow &)=delete
unsigned getMask() const
Gets the mask for this window.
Definition VDPVRAM.hh:145
std::pair< std::span< const byte, size/2 >, std::span< const byte, size/2 > > getReadAreaPlanar(unsigned index) const
Similar to getReadArea(), but now with planar addressing mode.
Definition VDPVRAM.hh:243
void setObserver(VRAMObserver *newObserver)
Register an observer on this VRAM window.
Definition VDPVRAM.hh:289
std::span< const byte, size > getReadArea(unsigned index) const
Gets a span of a contiguous part of the VRAM.
Definition VDPVRAM.hh:226
void resetObserver()
Unregister the observer of this VRAM window.
Definition VDPVRAM.hh:295
constexpr auto floodRight(std::unsigned_integral auto x) noexcept
Returns the smallest number of the form 2^n-1 that is greater or equal to the given number.
Definition Math.hh:32
This file implemented 3 utility functions:
Definition Autofire.cc:9
uint8_t byte
8 bit unsigned integer
Definition openmsx.hh:26