libata: fix ATAPI DMA alignment issues
ATAPI needs to be padded to next 4 byte boundary, if misaligned.
Original work by me, many fixes from Tejun Heo.
diff --git a/drivers/scsi/libata-scsi.c b/drivers/scsi/libata-scsi.c
index 104fd9a..ee3f105 100644
--- a/drivers/scsi/libata-scsi.c
+++ b/drivers/scsi/libata-scsi.c
@@ -150,10 +150,10 @@
qc->scsidone = done;
if (cmd->use_sg) {
- qc->sg = (struct scatterlist *) cmd->request_buffer;
+ qc->__sg = (struct scatterlist *) cmd->request_buffer;
qc->n_elem = cmd->use_sg;
} else {
- qc->sg = &qc->sgent;
+ qc->__sg = &qc->sgent;
qc->n_elem = 1;
}
} else {
@@ -364,6 +364,16 @@
*/
blk_queue_max_sectors(sdev->request_queue, 2048);
}
+
+ /*
+ * SATA DMA transfers must be multiples of 4 byte, so
+ * we need to pad ATAPI transfers using an extra sg.
+ * Decrement max hw segments accordingly.
+ */
+ if (dev->class == ATA_DEV_ATAPI) {
+ request_queue_t *q = sdev->request_queue;
+ blk_queue_max_hw_segments(q, q->max_hw_segments - 1);
+ }
}
return 0; /* scsi layer doesn't check return value, sigh */