sata_mv: workaround for multi_count errata sata24

Workaround for errata SATA#24 in sata_mv.
This errata affects WRITE_MULTI* commands when
the device multi_count produces a DRQ block size >= 4Kbytes.

We work around it here by converting such operations
into ordinary PIO_WRITEs instead.

Note that this might result in a PIO FUA write unavoidably being converted
into a non-FUA write.  In practice, any system using FUA is also going to be
using DMA rather than PIO, so this shouldn't affect anyone in the real world.

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 42 insertions, 2 deletions

diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index c7da6022c6b4..870dcfd82357 100644
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -1881,6 +1881,39 @@ static u8 mv_bmdma_status(struct ata_port *ap)
         return status;
 }
 
+static void mv_rw_multi_errata_sata24(struct ata_queued_cmd *qc)
+{
+        struct ata_taskfile *tf = &qc->tf;
+        /*
+         * Workaround for 88SX60x1 FEr SATA#24.
+         *
+         * Chip may corrupt WRITEs if multi_count >= 4kB.
+         * Note that READs are unaffected.
+         *
+         * It's not clear if this errata really means "4K bytes",
+         * or if it always happens for multi_count > 7
+         * regardless of device sector_size.
+         *
+         * So, for safety, any write with multi_count > 7
+         * gets converted here into a regular PIO write instead:
+         */
+        if ((tf->flags & ATA_TFLAG_WRITE) && is_multi_taskfile(tf)) {
+                if (qc->dev->multi_count > 7) {
+                        switch (tf->command) {
+                        case ATA_CMD_WRITE_MULTI:
+                                tf->command = ATA_CMD_PIO_WRITE;
+                                break;
+                        case ATA_CMD_WRITE_MULTI_FUA_EXT:
+                                tf->flags &= ~ATA_TFLAG_FUA; /* ugh */
+                                /* fall through */
+                        case ATA_CMD_WRITE_MULTI_EXT:
+                                tf->command = ATA_CMD_PIO_WRITE_EXT;
+                                break;
+                        }
+                }
+        }
+}
+
 /**
  *      mv_qc_prep - Host specific command preparation.
  *      @qc: queued command to prepare
@@ -1902,9 +1935,16 @@ static void mv_qc_prep(struct ata_queued_cmd *qc)
         u16 flags = 0;
         unsigned in_index;
 
-        if ((tf->protocol != ATA_PROT_DMA) &&
-            (tf->protocol != ATA_PROT_NCQ))
+        switch (tf->protocol) {
+        case ATA_PROT_DMA:
+        case ATA_PROT_NCQ:
+                break;  /* continue below */
+        case ATA_PROT_PIO:
+                mv_rw_multi_errata_sata24(qc);
                 return;
+        default:
+                return;
+        }
 
         /* Fill in command request block
          */