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 #include <linux/kernel.h>
  25 #include <linux/mm.h>
  26 #include "osd.h"
  27 #include "logging.h"
  28 #include "RingBuffer.h"
  29
  30
  31 /* #defines */
  32
  33
  34 /* Amount of space to write to */
  35 #define BYTES_AVAIL_TO_WRITE(r, w, z) ((w) >= (r))?((z) - ((w) - (r))):((r) - (w))
  36
  37
  38 /*++
  39
  40 Name:
  41         GetRingBufferAvailBytes()
  42
  43 Description:
  44         Get number of bytes available to read and to write to
  45         for the specified ring buffer
  46
  47 --*/
  48 static inline void
  49 GetRingBufferAvailBytes(RING_BUFFER_INFO *rbi, u32 *read, u32 *write)
  50 {
  51         u32 read_loc,write_loc;
  52
  53         /* Capture the read/write indices before they changed */
  54         read_loc = rbi->RingBuffer->ReadIndex;
  55         write_loc = rbi->RingBuffer->WriteIndex;
  56
  57         *write = BYTES_AVAIL_TO_WRITE(read_loc, write_loc, rbi->RingDataSize);
  58         *read = rbi->RingDataSize - *write;
  59 }
  60
  61 /*++
  62
  63 Name:
  64         GetNextWriteLocation()
  65
  66 Description:
  67         Get the next write location for the specified ring buffer
  68
  69 --*/
  70 static inline u32
  71 GetNextWriteLocation(RING_BUFFER_INFO* RingInfo)
  72 {
  73         u32 next = RingInfo->RingBuffer->WriteIndex;
  74
  75         ASSERT(next < RingInfo->RingDataSize);
  76
  77         return next;
  78 }
  79
  80 /*++
  81
  82 Name:
  83         SetNextWriteLocation()
  84
  85 Description:
  86         Set the next write location for the specified ring buffer
  87
  88 --*/
  89 static inline void
  90 SetNextWriteLocation(RING_BUFFER_INFO* RingInfo, u32 NextWriteLocation)
  91 {
  92         RingInfo->RingBuffer->WriteIndex = NextWriteLocation;
  93 }
  94
  95 /*++
  96
  97 Name:
  98         GetNextReadLocation()
  99
 100 Description:
 101         Get the next read location for the specified ring buffer
 102
 103 --*/
 104 static inline u32
 105 GetNextReadLocation(RING_BUFFER_INFO* RingInfo)
 106 {
 107         u32 next = RingInfo->RingBuffer->ReadIndex;
 108
 109         ASSERT(next < RingInfo->RingDataSize);
 110
 111         return next;
 112 }
 113
 114 /*++
 115
 116 Name:
 117         GetNextReadLocationWithOffset()
 118
 119 Description:
 120         Get the next read location + offset for the specified ring buffer.
 121         This allows the caller to skip
 122
 123 --*/
 124 static inline u32
 125 GetNextReadLocationWithOffset(RING_BUFFER_INFO* RingInfo, u32 Offset)
 126 {
 127         u32 next = RingInfo->RingBuffer->ReadIndex;
 128
 129         ASSERT(next < RingInfo->RingDataSize);
 130         next += Offset;
 131         next %= RingInfo->RingDataSize;
 132
 133         return next;
 134 }
 135
 136 /*++
 137
 138 Name:
 139         SetNextReadLocation()
 140
 141 Description:
 142         Set the next read location for the specified ring buffer
 143
 144 --*/
 145 static inline void
 146 SetNextReadLocation(RING_BUFFER_INFO* RingInfo, u32 NextReadLocation)
 147 {
 148         RingInfo->RingBuffer->ReadIndex = NextReadLocation;
 149 }
 150
 151
 152 /*++
 153
 154 Name:
 155         GetRingBuffer()
 156
 157 Description:
 158         Get the start of the ring buffer
 159
 160 --*/
 161 static inline void *
 162 GetRingBuffer(RING_BUFFER_INFO* RingInfo)
 163 {
 164         return (void *)RingInfo->RingBuffer->Buffer;
 165 }
 166
 167
 168 /*++
 169
 170 Name:
 171         GetRingBufferSize()
 172
 173 Description:
 174         Get the size of the ring buffer
 175
 176 --*/
 177 static inline u32
 178 GetRingBufferSize(RING_BUFFER_INFO* RingInfo)
 179 {
 180         return RingInfo->RingDataSize;
 181 }
 182
 183 /*++
 184
 185 Name:
 186         GetRingBufferIndices()
 187
 188 Description:
 189         Get the read and write indices as u64 of the specified ring buffer
 190
 191 --*/
 192 static inline u64
 193 GetRingBufferIndices(RING_BUFFER_INFO* RingInfo)
 194 {
 195         return (u64)RingInfo->RingBuffer->WriteIndex << 32;
 196 }
 197
 198
 199 /*++
 200
 201 Name:
 202         DumpRingInfo()
 203
 204 Description:
 205         Dump out to console the ring buffer info
 206
 207 --*/
 208 void DumpRingInfo(RING_BUFFER_INFO *RingInfo, char *Prefix)
 209 {
 210         u32 bytesAvailToWrite;
 211         u32 bytesAvailToRead;
 212
 213         GetRingBufferAvailBytes(RingInfo, &bytesAvailToRead, &bytesAvailToWrite);
 214
 215         DPRINT(VMBUS, DEBUG_RING_LVL, "%s <<ringinfo %p buffer %p avail write %u avail read %u read idx %u write idx %u>>",
 216                 Prefix,
 217                 RingInfo,
 218                 RingInfo->RingBuffer->Buffer,
 219                 bytesAvailToWrite,
 220                 bytesAvailToRead,
 221                 RingInfo->RingBuffer->ReadIndex,
 222                 RingInfo->RingBuffer->WriteIndex);
 223 }
 224
 225
 226 /* Internal routines */
 227
 228 static u32
 229 CopyToRingBuffer(
 230         RING_BUFFER_INFO        *RingInfo,
 231         u32                             StartWriteOffset,
 232         void *                          Src,
 233         u32                             SrcLen);
 234
 235 static u32
 236 CopyFromRingBuffer(
 237         RING_BUFFER_INFO        *RingInfo,
 238         void *                          Dest,
 239         u32                             DestLen,
 240         u32                             StartReadOffset);
 241
 242
 243
 244 /*++
 245
 246 Name:
 247         RingBufferGetDebugInfo()
 248
 249 Description:
 250         Get various debug metrics for the specified ring buffer
 251
 252 --*/
 253 void RingBufferGetDebugInfo(RING_BUFFER_INFO *RingInfo,
 254                             RING_BUFFER_DEBUG_INFO *DebugInfo)
 255 {
 256         u32 bytesAvailToWrite;
 257         u32 bytesAvailToRead;
 258
 259         if (RingInfo->RingBuffer)
 260         {
 261                 GetRingBufferAvailBytes(RingInfo, &bytesAvailToRead, &bytesAvailToWrite);
 262
 263                 DebugInfo->BytesAvailToRead = bytesAvailToRead;
 264                 DebugInfo->BytesAvailToWrite = bytesAvailToWrite;
 265                 DebugInfo->CurrentReadIndex = RingInfo->RingBuffer->ReadIndex;
 266                 DebugInfo->CurrentWriteIndex = RingInfo->RingBuffer->WriteIndex;
 267
 268                 DebugInfo->CurrentInterruptMask = RingInfo->RingBuffer->InterruptMask;
 269         }
 270 }
 271
 272
 273 /*++
 274
 275 Name:
 276         GetRingBufferInterruptMask()
 277
 278 Description:
 279         Get the interrupt mask for the specified ring buffer
 280
 281 --*/
 282 u32 GetRingBufferInterruptMask(RING_BUFFER_INFO *rbi)
 283 {
 284         return rbi->RingBuffer->InterruptMask;
 285 }
 286
 287 /*++
 288
 289 Name:
 290         RingBufferInit()
 291
 292 Description:
 293         Initialize the ring buffer
 294
 295 --*/
 296 int RingBufferInit(RING_BUFFER_INFO *RingInfo, void *Buffer, u32 BufferLen)
 297 {
 298         ASSERT(sizeof(RING_BUFFER) == PAGE_SIZE);
 299
 300         memset(RingInfo, 0, sizeof(RING_BUFFER_INFO));
 301
 302         RingInfo->RingBuffer = (RING_BUFFER*)Buffer;
 303         RingInfo->RingBuffer->ReadIndex = RingInfo->RingBuffer->WriteIndex = 0;
 304
 305         RingInfo->RingSize = BufferLen;
 306         RingInfo->RingDataSize = BufferLen - sizeof(RING_BUFFER);
 307
 308         spin_lock_init(&RingInfo->ring_lock);
 309
 310         return 0;
 311 }
 312
 313 /*++
 314
 315 Name:
 316         RingBufferCleanup()
 317
 318 Description:
 319         Cleanup the ring buffer
 320
 321 --*/
 322 void RingBufferCleanup(RING_BUFFER_INFO* RingInfo)
 323 {
 324 }
 325
 326 /*++
 327
 328 Name:
 329         RingBufferWrite()
 330
 331 Description:
 332         Write to the ring buffer
 333
 334 --*/
 335 int RingBufferWrite(RING_BUFFER_INFO *OutRingInfo,
 336                     struct scatterlist *sglist, u32 sgcount)
 337 {
 338         int i=0;
 339         u32 byteAvailToWrite;
 340         u32 byteAvailToRead;
 341         u32 totalBytesToWrite=0;
 342
 343         struct scatterlist *sg;
 344         volatile u32 nextWriteLocation;
 345         u64 prevIndices=0;
 346         unsigned long flags;
 347
 348         DPRINT_ENTER(VMBUS);
 349
 350         for_each_sg(sglist, sg, sgcount, i)
 351         {
 352                 totalBytesToWrite += sg->length;
 353         }
 354
 355         totalBytesToWrite += sizeof(u64);
 356
 357         spin_lock_irqsave(&OutRingInfo->ring_lock, flags);
 358
 359         GetRingBufferAvailBytes(OutRingInfo, &byteAvailToRead, &byteAvailToWrite);
 360
 361         DPRINT_DBG(VMBUS, "Writing %u bytes...", totalBytesToWrite);
 362
 363         /* DumpRingInfo(OutRingInfo, "BEFORE "); */
 364
 365         /* If there is only room for the packet, assume it is full. Otherwise, the next time around, we think the ring buffer */
 366         /* is empty since the read index == write index */
 367         if (byteAvailToWrite <= totalBytesToWrite)
 368         {
 369                 DPRINT_DBG(VMBUS, "No more space left on outbound ring buffer (needed %u, avail %u)", totalBytesToWrite, byteAvailToWrite);
 370
 371                 spin_unlock_irqrestore(&OutRingInfo->ring_lock, flags);
 372
 373                 DPRINT_EXIT(VMBUS);
 374
 375                 return -1;
 376         }
 377
 378         /* Write to the ring buffer */
 379         nextWriteLocation = GetNextWriteLocation(OutRingInfo);
 380
 381         for_each_sg(sglist, sg, sgcount, i)
 382         {
 383                 nextWriteLocation = CopyToRingBuffer(OutRingInfo,
 384                                                      nextWriteLocation,
 385                                                      sg_virt(sg),
 386                                                      sg->length);
 387         }
 388
 389         /* Set previous packet start */
 390         prevIndices = GetRingBufferIndices(OutRingInfo);
 391
 392         nextWriteLocation = CopyToRingBuffer(OutRingInfo,
 393                                              nextWriteLocation,
 394                                              &prevIndices,
 395                                              sizeof(u64));
 396
 397         /* Make sure we flush all writes before updating the writeIndex */
 398         mb();
 399
 400         /* Now, update the write location */
 401         SetNextWriteLocation(OutRingInfo, nextWriteLocation);
 402
 403         /* DumpRingInfo(OutRingInfo, "AFTER "); */
 404
 405         spin_unlock_irqrestore(&OutRingInfo->ring_lock, flags);
 406
 407         DPRINT_EXIT(VMBUS);
 408
 409         return 0;
 410 }
 411
 412
 413 /*++
 414
 415 Name:
 416         RingBufferPeek()
 417
 418 Description:
 419         Read without advancing the read index
 420
 421 --*/
 422 int RingBufferPeek(RING_BUFFER_INFO *InRingInfo, void *Buffer, u32 BufferLen)
 423 {
 424         u32 bytesAvailToWrite;
 425         u32 bytesAvailToRead;
 426         u32 nextReadLocation=0;
 427         unsigned long flags;
 428
 429         spin_lock_irqsave(&InRingInfo->ring_lock, flags);
 430
 431         GetRingBufferAvailBytes(InRingInfo, &bytesAvailToRead, &bytesAvailToWrite);
 432
 433         /* Make sure there is something to read */
 434         if (bytesAvailToRead < BufferLen )
 435         {
 436                 /* DPRINT_DBG(VMBUS, "got callback but not enough to read <avail to read %d read size %d>!!", bytesAvailToRead, BufferLen); */
 437
 438                 spin_unlock_irqrestore(&InRingInfo->ring_lock, flags);
 439
 440                 return -1;
 441         }
 442
 443         /* Convert to byte offset */
 444         nextReadLocation = GetNextReadLocation(InRingInfo);
 445
 446         nextReadLocation = CopyFromRingBuffer(InRingInfo,
 447                                                                                         Buffer,
 448                                                                                         BufferLen,
 449                                                                                         nextReadLocation);
 450
 451         spin_unlock_irqrestore(&InRingInfo->ring_lock, flags);
 452
 453         return 0;
 454 }
 455
 456
 457 /*++
 458
 459 Name:
 460         RingBufferRead()
 461
 462 Description:
 463         Read and advance the read index
 464
 465 --*/
 466 int RingBufferRead(RING_BUFFER_INFO *InRingInfo, void *Buffer,
 467                    u32 BufferLen, u32 Offset)
 468 {
 469         u32 bytesAvailToWrite;
 470         u32 bytesAvailToRead;
 471         u32 nextReadLocation=0;
 472         u64 prevIndices=0;
 473         unsigned long flags;
 474
 475         ASSERT(BufferLen > 0);
 476
 477         spin_lock_irqsave(&InRingInfo->ring_lock, flags);
 478
 479         GetRingBufferAvailBytes(InRingInfo, &bytesAvailToRead, &bytesAvailToWrite);
 480
 481         DPRINT_DBG(VMBUS, "Reading %u bytes...", BufferLen);
 482
 483         /* DumpRingInfo(InRingInfo, "BEFORE "); */
 484
 485         /* Make sure there is something to read */
 486         if (bytesAvailToRead < BufferLen )
 487         {
 488                 DPRINT_DBG(VMBUS, "got callback but not enough to read <avail to read %d read size %d>!!", bytesAvailToRead, BufferLen);
 489
 490                 spin_unlock_irqrestore(&InRingInfo->ring_lock, flags);
 491
 492                 return -1;
 493         }
 494
 495         nextReadLocation = GetNextReadLocationWithOffset(InRingInfo, Offset);
 496
 497         nextReadLocation = CopyFromRingBuffer(InRingInfo,
 498                                                                                         Buffer,
 499                                                                                         BufferLen,
 500                                                                                         nextReadLocation);
 501
 502         nextReadLocation = CopyFromRingBuffer(InRingInfo,
 503                                                                                         &prevIndices,
 504                                                                                         sizeof(u64),
 505                                                                                         nextReadLocation);
 506
 507         /* Make sure all reads are done before we update the read index since */
 508         /* the writer may start writing to the read area once the read index is updated */
 509         mb();
 510
 511         /* Update the read index */
 512         SetNextReadLocation(InRingInfo, nextReadLocation);
 513
 514         /* DumpRingInfo(InRingInfo, "AFTER "); */
 515
 516         spin_unlock_irqrestore(&InRingInfo->ring_lock, flags);
 517
 518         return 0;
 519 }
 520
 521
 522 /*++
 523
 524 Name:
 525         CopyToRingBuffer()
 526
 527 Description:
 528         Helper routine to copy from source to ring buffer.
 529         Assume there is enough room. Handles wrap-around in dest case only!!
 530
 531 --*/
 532 static u32
 533 CopyToRingBuffer(
 534         RING_BUFFER_INFO        *RingInfo,
 535         u32                             StartWriteOffset,
 536         void *                          Src,
 537         u32                             SrcLen)
 538 {
 539         void * ringBuffer=GetRingBuffer(RingInfo);
 540         u32 ringBufferSize=GetRingBufferSize(RingInfo);
 541         u32 fragLen;
 542
 543         if (SrcLen > ringBufferSize - StartWriteOffset) /* wrap-around detected! */
 544         {
 545                 DPRINT_DBG(VMBUS, "wrap-around detected!");
 546
 547                 fragLen = ringBufferSize - StartWriteOffset;
 548                 memcpy(ringBuffer + StartWriteOffset, Src, fragLen);
 549                 memcpy(ringBuffer, Src + fragLen, SrcLen - fragLen);
 550         }
 551         else
 552         {
 553                 memcpy(ringBuffer + StartWriteOffset, Src, SrcLen);
 554         }
 555
 556         StartWriteOffset += SrcLen;
 557         StartWriteOffset %= ringBufferSize;
 558
 559         return StartWriteOffset;
 560 }
 561
 562
 563 /*++
 564
 565 Name:
 566         CopyFromRingBuffer()
 567
 568 Description:
 569         Helper routine to copy to source from ring buffer.
 570         Assume there is enough room. Handles wrap-around in src case only!!
 571
 572 --*/
 573 static u32
 574 CopyFromRingBuffer(
 575         RING_BUFFER_INFO        *RingInfo,
 576         void *                          Dest,
 577         u32                             DestLen,
 578         u32                             StartReadOffset)
 579 {
 580         void * ringBuffer=GetRingBuffer(RingInfo);
 581         u32 ringBufferSize=GetRingBufferSize(RingInfo);
 582
 583         u32 fragLen;
 584
 585         if (DestLen > ringBufferSize - StartReadOffset) /* wrap-around detected at the src */
 586         {
 587                 DPRINT_DBG(VMBUS, "src wrap-around detected!");
 588
 589                 fragLen = ringBufferSize - StartReadOffset;
 590
 591                 memcpy(Dest, ringBuffer + StartReadOffset, fragLen);
 592                 memcpy(Dest + fragLen, ringBuffer, DestLen - fragLen);
 593         }
 594         else
 595         {
 596                 memcpy(Dest, ringBuffer + StartReadOffset, DestLen);
 597         }
 598
 599         StartReadOffset += DestLen;
 600         StartReadOffset %= ringBufferSize;
 601
 602         return StartReadOffset;
 603 }
 604
 605
 606 /* eof */