drivers/staging/hv/ring_buffer.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 "ring_buffer.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(struct hv_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(struct hv_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(struct hv_ring_buffer_info *RingInfo,
  91                      u32 NextWriteLocation)
  92 {
  93         RingInfo->RingBuffer->WriteIndex = NextWriteLocation;
  94 }
  95
  96 /*++
  97
  98 Name:
  99         GetNextReadLocation()
 100
 101 Description:
 102         Get the next read location for the specified ring buffer
 103
 104 --*/
 105 static inline u32
 106 GetNextReadLocation(struct hv_ring_buffer_info *RingInfo)
 107 {
 108         u32 next = RingInfo->RingBuffer->ReadIndex;
 109
 110         /* ASSERT(next < RingInfo->RingDataSize); */
 111
 112         return next;
 113 }
 114
 115 /*++
 116
 117 Name:
 118         GetNextReadLocationWithOffset()
 119
 120 Description:
 121         Get the next read location + offset for the specified ring buffer.
 122         This allows the caller to skip
 123
 124 --*/
 125 static inline u32
 126 GetNextReadLocationWithOffset(struct hv_ring_buffer_info *RingInfo, u32 Offset)
 127 {
 128         u32 next = RingInfo->RingBuffer->ReadIndex;
 129
 130         /* ASSERT(next < RingInfo->RingDataSize); */
 131         next += Offset;
 132         next %= RingInfo->RingDataSize;
 133
 134         return next;
 135 }
 136
 137 /*++
 138
 139 Name:
 140         SetNextReadLocation()
 141
 142 Description:
 143         Set the next read location for the specified ring buffer
 144
 145 --*/
 146 static inline void
 147 SetNextReadLocation(struct hv_ring_buffer_info *RingInfo, u32 NextReadLocation)
 148 {
 149         RingInfo->RingBuffer->ReadIndex = NextReadLocation;
 150 }
 151
 152
 153 /*++
 154
 155 Name:
 156         GetRingBuffer()
 157
 158 Description:
 159         Get the start of the ring buffer
 160
 161 --*/
 162 static inline void *
 163 GetRingBuffer(struct hv_ring_buffer_info *RingInfo)
 164 {
 165         return (void *)RingInfo->RingBuffer->Buffer;
 166 }
 167
 168
 169 /*++
 170
 171 Name:
 172         GetRingBufferSize()
 173
 174 Description:
 175         Get the size of the ring buffer
 176
 177 --*/
 178 static inline u32
 179 GetRingBufferSize(struct hv_ring_buffer_info *RingInfo)
 180 {
 181         return RingInfo->RingDataSize;
 182 }
 183
 184 /*++
 185
 186 Name:
 187         GetRingBufferIndices()
 188
 189 Description:
 190         Get the read and write indices as u64 of the specified ring buffer
 191
 192 --*/
 193 static inline u64
 194 GetRingBufferIndices(struct hv_ring_buffer_info *RingInfo)
 195 {
 196         return (u64)RingInfo->RingBuffer->WriteIndex << 32;
 197 }
 198
 199
 200 /*++
 201
 202 Name:
 203         DumpRingInfo()
 204
 205 Description:
 206         Dump out to console the ring buffer info
 207
 208 --*/
 209 void DumpRingInfo(struct hv_ring_buffer_info *RingInfo, char *Prefix)
 210 {
 211         u32 bytesAvailToWrite;
 212         u32 bytesAvailToRead;
 213
 214         GetRingBufferAvailBytes(RingInfo,
 215         &bytesAvailToRead,
 216         &bytesAvailToWrite);
 217
 218         DPRINT(VMBUS,
 219                 DEBUG_RING_LVL,
 220                 "%s <<ringinfo %p buffer %p avail write %u "
 221                 "avail read %u read idx %u write idx %u>>",
 222                 Prefix,
 223                 RingInfo,
 224                 RingInfo->RingBuffer->Buffer,
 225                 bytesAvailToWrite,
 226                 bytesAvailToRead,
 227                 RingInfo->RingBuffer->ReadIndex,
 228                 RingInfo->RingBuffer->WriteIndex);
 229 }
 230
 231
 232 /* Internal routines */
 233
 234 static u32
 235 CopyToRingBuffer(
 236         struct hv_ring_buffer_info      *RingInfo,
 237         u32                             StartWriteOffset,
 238         void                            *Src,
 239         u32                             SrcLen);
 240
 241 static u32
 242 CopyFromRingBuffer(
 243         struct hv_ring_buffer_info      *RingInfo,
 244         void                            *Dest,
 245         u32                             DestLen,
 246         u32                             StartReadOffset);
 247
 248
 249
 250 /*++
 251
 252 Name:
 253         RingBufferGetDebugInfo()
 254
 255 Description:
 256         Get various debug metrics for the specified ring buffer
 257
 258 --*/
 259 void RingBufferGetDebugInfo(struct hv_ring_buffer_info *RingInfo,
 260                             struct hv_ring_buffer_debug_info *debug_info)
 261 {
 262         u32 bytesAvailToWrite;
 263         u32 bytesAvailToRead;
 264
 265         if (RingInfo->RingBuffer) {
 266                 GetRingBufferAvailBytes(RingInfo,
 267                                         &bytesAvailToRead,
 268                                         &bytesAvailToWrite);
 269
 270                 debug_info->BytesAvailToRead = bytesAvailToRead;
 271                 debug_info->BytesAvailToWrite = bytesAvailToWrite;
 272                 debug_info->CurrentReadIndex = RingInfo->RingBuffer->ReadIndex;
 273                 debug_info->CurrentWriteIndex = RingInfo->RingBuffer->WriteIndex;
 274                 debug_info->CurrentInterruptMask = RingInfo->RingBuffer->InterruptMask;
 275         }
 276 }
 277
 278
 279 /*++
 280
 281 Name:
 282         GetRingBufferInterruptMask()
 283
 284 Description:
 285         Get the interrupt mask for the specified ring buffer
 286
 287 --*/
 288 u32 GetRingBufferInterruptMask(struct hv_ring_buffer_info *rbi)
 289 {
 290         return rbi->RingBuffer->InterruptMask;
 291 }
 292
 293 /*++
 294
 295 Name:
 296         RingBufferInit()
 297
 298 Description:
 299         Initialize the ring buffer
 300
 301 --*/
 302 int RingBufferInit(struct hv_ring_buffer_info *RingInfo, void *Buffer, u32 BufferLen)
 303 {
 304         if (sizeof(struct hv_ring_buffer) != PAGE_SIZE)
 305                 return -EINVAL;
 306
 307         memset(RingInfo, 0, sizeof(struct hv_ring_buffer_info));
 308
 309         RingInfo->RingBuffer = (struct hv_ring_buffer *)Buffer;
 310         RingInfo->RingBuffer->ReadIndex = RingInfo->RingBuffer->WriteIndex = 0;
 311
 312         RingInfo->RingSize = BufferLen;
 313         RingInfo->RingDataSize = BufferLen - sizeof(struct hv_ring_buffer);
 314
 315         spin_lock_init(&RingInfo->ring_lock);
 316
 317         return 0;
 318 }
 319
 320 /*++
 321
 322 Name:
 323         RingBufferCleanup()
 324
 325 Description:
 326         Cleanup the ring buffer
 327
 328 --*/
 329 void RingBufferCleanup(struct hv_ring_buffer_info *RingInfo)
 330 {
 331 }
 332
 333 /*++
 334
 335 Name:
 336         RingBufferWrite()
 337
 338 Description:
 339         Write to the ring buffer
 340
 341 --*/
 342 int RingBufferWrite(struct hv_ring_buffer_info *OutRingInfo,
 343                     struct scatterlist *sglist, u32 sgcount)
 344 {
 345         int i = 0;
 346         u32 byteAvailToWrite;
 347         u32 byteAvailToRead;
 348         u32 totalBytesToWrite = 0;
 349
 350         struct scatterlist *sg;
 351         volatile u32 nextWriteLocation;
 352         u64 prevIndices = 0;
 353         unsigned long flags;
 354
 355         for_each_sg(sglist, sg, sgcount, i)
 356         {
 357                 totalBytesToWrite += sg->length;
 358         }
 359
 360         totalBytesToWrite += sizeof(u64);
 361
 362         spin_lock_irqsave(&OutRingInfo->ring_lock, flags);
 363
 364         GetRingBufferAvailBytes(OutRingInfo,
 365                                 &byteAvailToRead,
 366                                 &byteAvailToWrite);
 367
 368         DPRINT_DBG(VMBUS, "Writing %u bytes...", totalBytesToWrite);
 369
 370         /* DumpRingInfo(OutRingInfo, "BEFORE "); */
 371
 372         /* If there is only room for the packet, assume it is full. */
 373         /* Otherwise, the next time around, we think the ring buffer */
 374         /* is empty since the read index == write index */
 375         if (byteAvailToWrite <= totalBytesToWrite) {
 376                 DPRINT_DBG(VMBUS,
 377                         "No more space left on outbound ring buffer "
 378                         "(needed %u, avail %u)",
 379                         totalBytesToWrite,
 380                         byteAvailToWrite);
 381
 382                 spin_unlock_irqrestore(&OutRingInfo->ring_lock, flags);
 383                 return -1;
 384         }
 385
 386         /* Write to the ring buffer */
 387         nextWriteLocation = GetNextWriteLocation(OutRingInfo);
 388
 389         for_each_sg(sglist, sg, sgcount, i)
 390         {
 391                 nextWriteLocation = CopyToRingBuffer(OutRingInfo,
 392                                                      nextWriteLocation,
 393                                                      sg_virt(sg),
 394                                                      sg->length);
 395         }
 396
 397         /* Set previous packet start */
 398         prevIndices = GetRingBufferIndices(OutRingInfo);
 399
 400         nextWriteLocation = CopyToRingBuffer(OutRingInfo,
 401                                              nextWriteLocation,
 402                                              &prevIndices,
 403                                              sizeof(u64));
 404
 405         /* Make sure we flush all writes before updating the writeIndex */
 406         mb();
 407
 408         /* Now, update the write location */
 409         SetNextWriteLocation(OutRingInfo, nextWriteLocation);
 410
 411         /* DumpRingInfo(OutRingInfo, "AFTER "); */
 412
 413         spin_unlock_irqrestore(&OutRingInfo->ring_lock, flags);
 414         return 0;
 415 }
 416
 417
 418 /*++
 419
 420 Name:
 421         RingBufferPeek()
 422
 423 Description:
 424         Read without advancing the read index
 425
 426 --*/
 427 int RingBufferPeek(struct hv_ring_buffer_info *InRingInfo, void *Buffer, u32 BufferLen)
 428 {
 429         u32 bytesAvailToWrite;
 430         u32 bytesAvailToRead;
 431         u32 nextReadLocation = 0;
 432         unsigned long flags;
 433
 434         spin_lock_irqsave(&InRingInfo->ring_lock, flags);
 435
 436         GetRingBufferAvailBytes(InRingInfo,
 437                                 &bytesAvailToRead,
 438                                 &bytesAvailToWrite);
 439
 440         /* Make sure there is something to read */
 441         if (bytesAvailToRead < BufferLen) {
 442                 /* DPRINT_DBG(VMBUS,
 443                         "got callback but not enough to read "
 444                         "<avail to read %d read size %d>!!",
 445                         bytesAvailToRead,
 446                         BufferLen); */
 447
 448                 spin_unlock_irqrestore(&InRingInfo->ring_lock, flags);
 449
 450                 return -1;
 451         }
 452
 453         /* Convert to byte offset */
 454         nextReadLocation = GetNextReadLocation(InRingInfo);
 455
 456         nextReadLocation = CopyFromRingBuffer(InRingInfo,
 457                                                 Buffer,
 458                                                 BufferLen,
 459                                                 nextReadLocation);
 460
 461         spin_unlock_irqrestore(&InRingInfo->ring_lock, flags);
 462
 463         return 0;
 464 }
 465
 466
 467 /*++
 468
 469 Name:
 470         RingBufferRead()
 471
 472 Description:
 473         Read and advance the read index
 474
 475 --*/
 476 int RingBufferRead(struct hv_ring_buffer_info *InRingInfo, void *Buffer,
 477                    u32 BufferLen, u32 Offset)
 478 {
 479         u32 bytesAvailToWrite;
 480         u32 bytesAvailToRead;
 481         u32 nextReadLocation = 0;
 482         u64 prevIndices = 0;
 483         unsigned long flags;
 484
 485         if (BufferLen <= 0)
 486                 return -EINVAL;
 487
 488         spin_lock_irqsave(&InRingInfo->ring_lock, flags);
 489
 490         GetRingBufferAvailBytes(InRingInfo,
 491                                 &bytesAvailToRead,
 492                                 &bytesAvailToWrite);
 493
 494         DPRINT_DBG(VMBUS, "Reading %u bytes...", BufferLen);
 495
 496         /* DumpRingInfo(InRingInfo, "BEFORE "); */
 497
 498         /* Make sure there is something to read */
 499         if (bytesAvailToRead < BufferLen) {
 500                 DPRINT_DBG(VMBUS,
 501                         "got callback but not enough to read "
 502                         "<avail to read %d read size %d>!!",
 503                         bytesAvailToRead,
 504                         BufferLen);
 505
 506                 spin_unlock_irqrestore(&InRingInfo->ring_lock, flags);
 507
 508                 return -1;
 509         }
 510
 511         nextReadLocation = GetNextReadLocationWithOffset(InRingInfo, Offset);
 512
 513         nextReadLocation = CopyFromRingBuffer(InRingInfo,
 514                                                 Buffer,
 515                                                 BufferLen,
 516                                                 nextReadLocation);
 517
 518         nextReadLocation = CopyFromRingBuffer(InRingInfo,
 519                                                 &prevIndices,
 520                                                 sizeof(u64),
 521                                                 nextReadLocation);
 522
 523         /* Make sure all reads are done before we update the read index since */
 524         /* the writer may start writing to the read area once the read index */
 525         /*is updated */
 526         mb();
 527
 528         /* Update the read index */
 529         SetNextReadLocation(InRingInfo, nextReadLocation);
 530
 531         /* DumpRingInfo(InRingInfo, "AFTER "); */
 532
 533         spin_unlock_irqrestore(&InRingInfo->ring_lock, flags);
 534
 535         return 0;
 536 }
 537
 538
 539 /*++
 540
 541 Name:
 542         CopyToRingBuffer()
 543
 544 Description:
 545         Helper routine to copy from source to ring buffer.
 546         Assume there is enough room. Handles wrap-around in dest case only!!
 547
 548 --*/
 549 static u32
 550 CopyToRingBuffer(
 551         struct hv_ring_buffer_info      *RingInfo,
 552         u32                             StartWriteOffset,
 553         void                            *Src,
 554         u32                             SrcLen)
 555 {
 556         void *ringBuffer = GetRingBuffer(RingInfo);
 557         u32 ringBufferSize = GetRingBufferSize(RingInfo);
 558         u32 fragLen;
 559
 560         /* wrap-around detected! */
 561         if (SrcLen > ringBufferSize - StartWriteOffset) {
 562                 DPRINT_DBG(VMBUS, "wrap-around detected!");
 563
 564                 fragLen = ringBufferSize - StartWriteOffset;
 565                 memcpy(ringBuffer + StartWriteOffset, Src, fragLen);
 566                 memcpy(ringBuffer, Src + fragLen, SrcLen - fragLen);
 567         } else
 568                 memcpy(ringBuffer + StartWriteOffset, Src, SrcLen);
 569
 570         StartWriteOffset += SrcLen;
 571         StartWriteOffset %= ringBufferSize;
 572
 573         return StartWriteOffset;
 574 }
 575
 576
 577 /*++
 578
 579 Name:
 580         CopyFromRingBuffer()
 581
 582 Description:
 583         Helper routine to copy to source from ring buffer.
 584         Assume there is enough room. Handles wrap-around in src case only!!
 585
 586 --*/
 587 static u32
 588 CopyFromRingBuffer(
 589         struct hv_ring_buffer_info      *RingInfo,
 590         void                            *Dest,
 591         u32                             DestLen,
 592         u32                             StartReadOffset)
 593 {
 594         void *ringBuffer = GetRingBuffer(RingInfo);
 595         u32 ringBufferSize = GetRingBufferSize(RingInfo);
 596
 597         u32 fragLen;
 598
 599         /* wrap-around detected at the src */
 600         if (DestLen > ringBufferSize - StartReadOffset) {
 601                 DPRINT_DBG(VMBUS, "src wrap-around detected!");
 602
 603                 fragLen = ringBufferSize - StartReadOffset;
 604
 605                 memcpy(Dest, ringBuffer + StartReadOffset, fragLen);
 606                 memcpy(Dest + fragLen, ringBuffer, DestLen - fragLen);
 607         } else
 608
 609                 memcpy(Dest, ringBuffer + StartReadOffset, DestLen);
 610
 611
 612         StartReadOffset += DestLen;
 613         StartReadOffset %= ringBufferSize;
 614
 615         return StartReadOffset;
 616 }
 617
 618
 619 /* eof */