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-rw-r--r--drivers/ata/libata-scsi.c35
1 files changed, 32 insertions, 3 deletions
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index a45f6ac3b245..a883bb03d4c7 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -2485,11 +2485,40 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc)
2485 if (!using_pio && ata_check_atapi_dma(qc)) 2485 if (!using_pio && ata_check_atapi_dma(qc))
2486 using_pio = 1; 2486 using_pio = 1;
2487 2487
2488 /* Some controller variants snoop this value for Packet transfers 2488 /* Some controller variants snoop this value for Packet
2489 to do state machine and FIFO management. Thus we want to set it 2489 * transfers to do state machine and FIFO management. Thus we
2490 properly, and for DMA where it is effectively meaningless */ 2490 * want to set it properly, and for DMA where it is
2491 * effectively meaningless.
2492 */
2491 nbytes = min(qc->nbytes, (unsigned int)63 * 1024); 2493 nbytes = min(qc->nbytes, (unsigned int)63 * 1024);
2492 2494
2495 /* Most ATAPI devices which honor transfer chunk size don't
2496 * behave according to the spec when odd chunk size which
2497 * matches the transfer length is specified. If the number of
2498 * bytes to transfer is 2n+1. According to the spec, what
2499 * should happen is to indicate that 2n+1 is going to be
2500 * transferred and transfer 2n+2 bytes where the last byte is
2501 * padding.
2502 *
2503 * In practice, this doesn't happen. ATAPI devices first
2504 * indicate and transfer 2n bytes and then indicate and
2505 * transfer 2 bytes where the last byte is padding.
2506 *
2507 * This inconsistency confuses several controllers which
2508 * perform PIO using DMA such as Intel AHCIs and sil3124/32.
2509 * These controllers use actual number of transferred bytes to
2510 * update DMA poitner and transfer of 4n+2 bytes make those
2511 * controller push DMA pointer by 4n+4 bytes because SATA data
2512 * FISes are aligned to 4 bytes. This causes data corruption
2513 * and buffer overrun.
2514 *
2515 * Always setting nbytes to even number solves this problem
2516 * because then ATAPI devices don't have to split data at 2n
2517 * boundaries.
2518 */
2519 if (nbytes & 0x1)
2520 nbytes++;
2521
2493 qc->tf.lbam = (nbytes & 0xFF); 2522 qc->tf.lbam = (nbytes & 0xFF);
2494 qc->tf.lbah = (nbytes >> 8); 2523 qc->tf.lbah = (nbytes >> 8);
2495 2524