drivers/staging/hv/RingBuffer.c

   1 /*
   2  *
   3  * Copyright (c) 2009, Microsoft Corporation.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms and conditions of the GNU General Public License,
   7  * version 2, as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  12  * more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along with
  15  * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  16  * Place - Suite 330, Boston, MA 02111-1307 USA.
  17  *
  18  * Authors:
  19  *   Haiyang Zhang <haiyangz@microsoft.com>
  20  *   Hank Janssen  <hjanssen@microsoft.com>
  21  *
  22  */
  23
  24
  25 #include "include/logging.h"
  26 #include "RingBuffer.h"
  27
  28 //
  29 // #defines
  30 //
  31
  32 // Amount of space to write to
  33 #define BYTES_AVAIL_TO_WRITE(r, w, z) ((w) >= (r))?((z) - ((w) - (r))):((r) - (w))
  34
  35
  36 /*++
  37
  38 Name:
  39         GetRingBufferAvailBytes()
  40
  41 Description:
  42         Get number of bytes available to read and to write to
  43         for the specified ring buffer
  44
  45 --*/
  46 static inline void
  47 GetRingBufferAvailBytes(RING_BUFFER_INFO *rbi, UINT32 *read, UINT32 *write)
  48 {
  49         UINT32 read_loc,write_loc;
  50
  51         // Capture the read/write indices before they changed
  52         read_loc = rbi->RingBuffer->ReadIndex;
  53         write_loc = rbi->RingBuffer->WriteIndex;
  54
  55         *write = BYTES_AVAIL_TO_WRITE(read_loc, write_loc, rbi->RingDataSize);
  56         *read = rbi->RingDataSize - *write;
  57 }
  58
  59 /*++
  60
  61 Name:
  62         GetNextWriteLocation()
  63
  64 Description:
  65         Get the next write location for the specified ring buffer
  66
  67 --*/
  68 static inline UINT32
  69 GetNextWriteLocation(RING_BUFFER_INFO* RingInfo)
  70 {
  71         UINT32 next = RingInfo->RingBuffer->WriteIndex;
  72
  73         ASSERT(next < RingInfo->RingDataSize);
  74
  75         return next;
  76 }
  77
  78 /*++
  79
  80 Name:
  81         SetNextWriteLocation()
  82
  83 Description:
  84         Set the next write location for the specified ring buffer
  85
  86 --*/
  87 static inline void
  88 SetNextWriteLocation(RING_BUFFER_INFO* RingInfo, UINT32 NextWriteLocation)
  89 {
  90         RingInfo->RingBuffer->WriteIndex = NextWriteLocation;
  91 }
  92
  93 /*++
  94
  95 Name:
  96         GetNextReadLocation()
  97
  98 Description:
  99         Get the next read location for the specified ring buffer
 100
 101 --*/
 102 static inline UINT32
 103 GetNextReadLocation(RING_BUFFER_INFO* RingInfo)
 104 {
 105         UINT32 next = RingInfo->RingBuffer->ReadIndex;
 106
 107         ASSERT(next < RingInfo->RingDataSize);
 108
 109         return next;
 110 }
 111
 112 /*++
 113
 114 Name:
 115         GetNextReadLocationWithOffset()
 116
 117 Description:
 118         Get the next read location + offset for the specified ring buffer.
 119         This allows the caller to skip
 120
 121 --*/
 122 static inline UINT32
 123 GetNextReadLocationWithOffset(RING_BUFFER_INFO* RingInfo, UINT32 Offset)
 124 {
 125         UINT32 next = RingInfo->RingBuffer->ReadIndex;
 126
 127         ASSERT(next < RingInfo->RingDataSize);
 128         next += Offset;
 129         next %= RingInfo->RingDataSize;
 130
 131         return next;
 132 }
 133
 134 /*++
 135
 136 Name:
 137         SetNextReadLocation()
 138
 139 Description:
 140         Set the next read location for the specified ring buffer
 141
 142 --*/
 143 static inline void
 144 SetNextReadLocation(RING_BUFFER_INFO* RingInfo, UINT32 NextReadLocation)
 145 {
 146         RingInfo->RingBuffer->ReadIndex = NextReadLocation;
 147 }
 148
 149
 150 /*++
 151
 152 Name:
 153         GetRingBuffer()
 154
 155 Description:
 156         Get the start of the ring buffer
 157
 158 --*/
 159 static inline void *
 160 GetRingBuffer(RING_BUFFER_INFO* RingInfo)
 161 {
 162         return (void *)RingInfo->RingBuffer->Buffer;
 163 }
 164
 165
 166 /*++
 167
 168 Name:
 169         GetRingBufferSize()
 170
 171 Description:
 172         Get the size of the ring buffer
 173
 174 --*/
 175 static inline UINT32
 176 GetRingBufferSize(RING_BUFFER_INFO* RingInfo)
 177 {
 178         return RingInfo->RingDataSize;
 179 }
 180
 181 /*++
 182
 183 Name:
 184         GetRingBufferIndices()
 185
 186 Description:
 187         Get the read and write indices as UINT64 of the specified ring buffer
 188
 189 --*/
 190 static inline UINT64
 191 GetRingBufferIndices(RING_BUFFER_INFO* RingInfo)
 192 {
 193         return ((UINT64)RingInfo->RingBuffer->WriteIndex << 32) || RingInfo->RingBuffer->ReadIndex;
 194 }
 195
 196
 197 /*++
 198
 199 Name:
 200         DumpRingInfo()
 201
 202 Description:
 203         Dump out to console the ring buffer info
 204
 205 --*/
 206 void
 207 DumpRingInfo(RING_BUFFER_INFO* RingInfo, char *Prefix)
 208 {
 209         UINT32 bytesAvailToWrite;
 210         UINT32 bytesAvailToRead;
 211
 212         GetRingBufferAvailBytes(RingInfo, &bytesAvailToRead, &bytesAvailToWrite);
 213
 214         DPRINT(VMBUS, DEBUG_RING_LVL, "%s <<ringinfo %p buffer %p avail write %u avail read %u read idx %u write idx %u>>",
 215                 Prefix,
 216                 RingInfo,
 217                 RingInfo->RingBuffer->Buffer,
 218                 bytesAvailToWrite,
 219                 bytesAvailToRead,
 220                 RingInfo->RingBuffer->ReadIndex,
 221                 RingInfo->RingBuffer->WriteIndex);
 222 }
 223
 224 //
 225 // Internal routines
 226 //
 227 static UINT32
 228 CopyToRingBuffer(
 229         RING_BUFFER_INFO        *RingInfo,
 230         UINT32                          StartWriteOffset,
 231         void *                          Src,
 232         UINT32                          SrcLen);
 233
 234 static UINT32
 235 CopyFromRingBuffer(
 236         RING_BUFFER_INFO        *RingInfo,
 237         void *                          Dest,
 238         UINT32                          DestLen,
 239         UINT32                          StartReadOffset);
 240
 241
 242
 243 /*++
 244
 245 Name:
 246         RingBufferGetDebugInfo()
 247
 248 Description:
 249         Get various debug metrics for the specified ring buffer
 250
 251 --*/
 252 void
 253 RingBufferGetDebugInfo(
 254         RING_BUFFER_INFO                *RingInfo,
 255         RING_BUFFER_DEBUG_INFO  *DebugInfo
 256         )
 257 {
 258         UINT32 bytesAvailToWrite;
 259         UINT32 bytesAvailToRead;
 260
 261         if (RingInfo->RingBuffer)
 262         {
 263                 GetRingBufferAvailBytes(RingInfo, &bytesAvailToRead, &bytesAvailToWrite);
 264
 265                 DebugInfo->BytesAvailToRead = bytesAvailToRead;
 266                 DebugInfo->BytesAvailToWrite = bytesAvailToWrite;
 267                 DebugInfo->CurrentReadIndex = RingInfo->RingBuffer->ReadIndex;
 268                 DebugInfo->CurrentWriteIndex = RingInfo->RingBuffer->WriteIndex;
 269
 270                 DebugInfo->CurrentInterruptMask = RingInfo->RingBuffer->InterruptMask;
 271         }
 272 }
 273
 274
 275 /*++
 276
 277 Name:
 278         GetRingBufferInterruptMask()
 279
 280 Description:
 281         Get the interrupt mask for the specified ring buffer
 282
 283 --*/
 284 UINT32
 285 GetRingBufferInterruptMask(
 286         RING_BUFFER_INFO *rbi
 287         )
 288 {
 289         return rbi->RingBuffer->InterruptMask;
 290 }
 291
 292 /*++
 293
 294 Name:
 295         RingBufferInit()
 296
 297 Description:
 298         Initialize the ring buffer
 299
 300 --*/
 301 int
 302 RingBufferInit(
 303         RING_BUFFER_INFO        *RingInfo,
 304         void                            *Buffer,
 305         UINT32                          BufferLen
 306         )
 307 {
 308         ASSERT(sizeof(RING_BUFFER) == PAGE_SIZE);
 309
 310         memset(RingInfo, 0, sizeof(RING_BUFFER_INFO));
 311
 312         RingInfo->RingBuffer = (RING_BUFFER*)Buffer;
 313         RingInfo->RingBuffer->ReadIndex = RingInfo->RingBuffer->WriteIndex = 0;
 314
 315         RingInfo->RingSize = BufferLen;
 316         RingInfo->RingDataSize = BufferLen - sizeof(RING_BUFFER);
 317
 318         RingInfo->RingLock = SpinlockCreate();
 319
 320         return 0;
 321 }
 322
 323 /*++
 324
 325 Name:
 326         RingBufferCleanup()
 327
 328 Description:
 329         Cleanup the ring buffer
 330
 331 --*/
 332 void
 333 RingBufferCleanup(
 334         RING_BUFFER_INFO* RingInfo
 335         )
 336 {
 337         SpinlockClose(RingInfo->RingLock);
 338 }
 339
 340 /*++
 341
 342 Name:
 343         RingBufferWrite()
 344
 345 Description:
 346         Write to the ring buffer
 347
 348 --*/
 349 int
 350 RingBufferWrite(
 351         RING_BUFFER_INFO*       OutRingInfo,
 352         SG_BUFFER_LIST          SgBuffers[],
 353         UINT32                          SgBufferCount
 354         )
 355 {
 356         int i=0;
 357         UINT32 byteAvailToWrite;
 358         UINT32 byteAvailToRead;
 359         UINT32 totalBytesToWrite=0;
 360
 361         volatile UINT32 nextWriteLocation;
 362         UINT64 prevIndices=0;
 363
 364         DPRINT_ENTER(VMBUS);
 365
 366         for (i=0; i < SgBufferCount; i++)
 367         {
 368                 totalBytesToWrite += SgBuffers[i].Length;
 369         }
 370
 371         totalBytesToWrite += sizeof(UINT64);
 372
 373         SpinlockAcquire(OutRingInfo->RingLock);
 374
 375         GetRingBufferAvailBytes(OutRingInfo, &byteAvailToRead, &byteAvailToWrite);
 376
 377         DPRINT_DBG(VMBUS, "Writing %u bytes...", totalBytesToWrite);
 378
 379         //DumpRingInfo(OutRingInfo, "BEFORE ");
 380
 381         // If there is only room for the packet, assume it is full. Otherwise, the next time around, we think the ring buffer
 382         // is empty since the read index == write index
 383         if (byteAvailToWrite <= totalBytesToWrite)
 384         {
 385                 DPRINT_DBG(VMBUS, "No more space left on outbound ring buffer (needed %u, avail %u)", totalBytesToWrite, byteAvailToWrite);
 386
 387                 SpinlockRelease(OutRingInfo->RingLock);
 388
 389                 DPRINT_EXIT(VMBUS);
 390
 391                 return -1;
 392         }
 393
 394         // Write to the ring buffer
 395         nextWriteLocation = GetNextWriteLocation(OutRingInfo);
 396
 397         for (i=0; i < SgBufferCount; i++)
 398         {
 399                  nextWriteLocation = CopyToRingBuffer(OutRingInfo,
 400                                                                                                 nextWriteLocation,
 401                                                                                                 SgBuffers[i].Data,
 402                                                                                                 SgBuffers[i].Length);
 403         }
 404
 405         // Set previous packet start
 406         prevIndices = GetRingBufferIndices(OutRingInfo);
 407
 408         nextWriteLocation = CopyToRingBuffer(OutRingInfo,
 409                                                                                                 nextWriteLocation,
 410                                                                                                 &prevIndices,
 411                                                                                                 sizeof(UINT64));
 412
 413         // Make sure we flush all writes before updating the writeIndex
 414         MemoryFence();
 415
 416         // Now, update the write location
 417         SetNextWriteLocation(OutRingInfo, nextWriteLocation);
 418
 419         //DumpRingInfo(OutRingInfo, "AFTER ");
 420
 421         SpinlockRelease(OutRingInfo->RingLock);
 422
 423         DPRINT_EXIT(VMBUS);
 424
 425         return 0;
 426 }
 427
 428
 429 /*++
 430
 431 Name:
 432         RingBufferPeek()
 433
 434 Description:
 435         Read without advancing the read index
 436
 437 --*/
 438 int
 439 RingBufferPeek(
 440         RING_BUFFER_INFO*       InRingInfo,
 441         void*                           Buffer,
 442         UINT32                          BufferLen
 443         )
 444 {
 445         UINT32 bytesAvailToWrite;
 446         UINT32 bytesAvailToRead;
 447         UINT32 nextReadLocation=0;
 448
 449         SpinlockAcquire(InRingInfo->RingLock);
 450
 451         GetRingBufferAvailBytes(InRingInfo, &bytesAvailToRead, &bytesAvailToWrite);
 452
 453         // Make sure there is something to read
 454         if (bytesAvailToRead < BufferLen )
 455         {
 456                 //DPRINT_DBG(VMBUS, "got callback but not enough to read <avail to read %d read size %d>!!", bytesAvailToRead, BufferLen);
 457
 458                 SpinlockRelease(InRingInfo->RingLock);
 459
 460                 return -1;
 461         }
 462
 463         // Convert to byte offset
 464         nextReadLocation = GetNextReadLocation(InRingInfo);
 465
 466         nextReadLocation = CopyFromRingBuffer(InRingInfo,
 467                                                                                         Buffer,
 468                                                                                         BufferLen,
 469                                                                                         nextReadLocation);
 470
 471         SpinlockRelease(InRingInfo->RingLock);
 472
 473         return 0;
 474 }
 475
 476
 477 /*++
 478
 479 Name:
 480         RingBufferRead()
 481
 482 Description:
 483         Read and advance the read index
 484
 485 --*/
 486 int
 487 RingBufferRead(
 488         RING_BUFFER_INFO*       InRingInfo,
 489         void *                          Buffer,
 490         UINT32                          BufferLen,
 491         UINT32                          Offset
 492         )
 493 {
 494         UINT32 bytesAvailToWrite;
 495         UINT32 bytesAvailToRead;
 496         UINT32 nextReadLocation=0;
 497         UINT64 prevIndices=0;
 498
 499         ASSERT(BufferLen > 0);
 500
 501         SpinlockAcquire(InRingInfo->RingLock);
 502
 503         GetRingBufferAvailBytes(InRingInfo, &bytesAvailToRead, &bytesAvailToWrite);
 504
 505         DPRINT_DBG(VMBUS, "Reading %u bytes...", BufferLen);
 506
 507         //DumpRingInfo(InRingInfo, "BEFORE ");
 508
 509         // Make sure there is something to read
 510         if (bytesAvailToRead < BufferLen )
 511         {
 512                 DPRINT_DBG(VMBUS, "got callback but not enough to read <avail to read %d read size %d>!!", bytesAvailToRead, BufferLen);
 513
 514                 SpinlockRelease(InRingInfo->RingLock);
 515
 516                 return -1;
 517         }
 518
 519         nextReadLocation = GetNextReadLocationWithOffset(InRingInfo, Offset);
 520
 521         nextReadLocation = CopyFromRingBuffer(InRingInfo,
 522                                                                                         Buffer,
 523                                                                                         BufferLen,
 524                                                                                         nextReadLocation);
 525
 526         nextReadLocation = CopyFromRingBuffer(InRingInfo,
 527                                                                                         &prevIndices,
 528                                                                                         sizeof(UINT64),
 529                                                                                         nextReadLocation);
 530
 531         // Make sure all reads are done before we update the read index since
 532         // the writer may start writing to the read area once the read index is updated
 533         MemoryFence();
 534
 535         // Update the read index
 536         SetNextReadLocation(InRingInfo, nextReadLocation);
 537
 538         //DumpRingInfo(InRingInfo, "AFTER ");
 539
 540         SpinlockRelease(InRingInfo->RingLock);
 541
 542         return 0;
 543 }
 544
 545
 546 /*++
 547
 548 Name:
 549         CopyToRingBuffer()
 550
 551 Description:
 552         Helper routine to copy from source to ring buffer.
 553         Assume there is enough room. Handles wrap-around in dest case only!!
 554
 555 --*/
 556 UINT32
 557 CopyToRingBuffer(
 558         RING_BUFFER_INFO        *RingInfo,
 559         UINT32                          StartWriteOffset,
 560         void *                          Src,
 561         UINT32                          SrcLen)
 562 {
 563         void * ringBuffer=GetRingBuffer(RingInfo);
 564         UINT32 ringBufferSize=GetRingBufferSize(RingInfo);
 565         UINT32 fragLen;
 566
 567         if (SrcLen > ringBufferSize - StartWriteOffset) // wrap-around detected!
 568         {
 569                 DPRINT_DBG(VMBUS, "wrap-around detected!");
 570
 571                 fragLen = ringBufferSize - StartWriteOffset;
 572                 memcpy(ringBuffer + StartWriteOffset, Src, fragLen);
 573                 memcpy(ringBuffer, Src + fragLen, SrcLen - fragLen);
 574         }
 575         else
 576         {
 577                 memcpy(ringBuffer + StartWriteOffset, Src, SrcLen);
 578         }
 579
 580         StartWriteOffset += SrcLen;
 581         StartWriteOffset %= ringBufferSize;
 582
 583         return StartWriteOffset;
 584 }
 585
 586
 587 /*++
 588
 589 Name:
 590         CopyFromRingBuffer()
 591
 592 Description:
 593         Helper routine to copy to source from ring buffer.
 594         Assume there is enough room. Handles wrap-around in src case only!!
 595
 596 --*/
 597 UINT32
 598 CopyFromRingBuffer(
 599         RING_BUFFER_INFO        *RingInfo,
 600         void *                          Dest,
 601         UINT32                          DestLen,
 602         UINT32                          StartReadOffset)
 603 {
 604         void * ringBuffer=GetRingBuffer(RingInfo);
 605         UINT32 ringBufferSize=GetRingBufferSize(RingInfo);
 606
 607         UINT32 fragLen;
 608
 609         if (DestLen > ringBufferSize - StartReadOffset) // wrap-around detected at the src
 610         {
 611                 DPRINT_DBG(VMBUS, "src wrap-around detected!");
 612
 613                 fragLen = ringBufferSize - StartReadOffset;
 614
 615                 memcpy(Dest, ringBuffer + StartReadOffset, fragLen);
 616                 memcpy(Dest + fragLen, ringBuffer, DestLen - fragLen);
 617         }
 618         else
 619         {
 620                 memcpy(Dest, ringBuffer + StartReadOffset, DestLen);
 621         }
 622
 623         StartReadOffset += DestLen;
 624         StartReadOffset %= ringBufferSize;
 625
 626         return StartReadOffset;
 627 }
 628
 629
 630 // eof