[libata] pio/dma flag bug fix, and cleanup

In the transfer-mode cleanup recently, the code that set flag
ATA_DFLAG_PIO disappeared.  Resurrect it.

Remove ATA_QCFLAG_DMA, it isn't needed.

Always set polling in the ->qc_issue function, rather than force
the user to do it when setting up an ata_queued_cmd.  This gives
maximum flexibility to the driver, letting the driver choose
whether or not to poll.

drivers/scsi/libata-core.c

@@ -1280,6 +1280,9 @@ static void ata_dev_set_mode(struct ata_port *ap, struct ata_device *dev)
 	if (!ata_dev_present(dev) || (ap->flags & ATA_FLAG_PORT_DISABLED))
 		return;
 
+	if (dev->xfer_shift == ATA_SHIFT_PIO)
+		dev->flags |= ATA_DFLAG_PIO;
+
 	ata_dev_set_xfermode(ap, dev);
 
 	base = base_from_shift(dev->xfer_shift);
@@ -2333,8 +2336,6 @@ struct ata_queued_cmd *ata_qc_new_init(struct ata_port *ap,
 
 		ata_tf_init(ap, &qc->tf, dev->devno);
 
-		if (likely((dev->flags & ATA_DFLAG_PIO) == 0))
-			qc->flags |= ATA_QCFLAG_DMA;
 		if (dev->flags & ATA_DFLAG_LBA48)
 			qc->tf.flags |= ATA_TFLAG_LBA48;
 	}
@@ -2473,6 +2474,7 @@ int ata_qc_issue_prot(struct ata_queued_cmd *qc)
 		break;
 
 	case ATA_PROT_ATAPI:
+		ata_qc_set_polling(qc);
 		ata_tf_to_host_nolock(ap, &qc->tf);
 		queue_work(ata_wq, &ap->packet_task);
 		break;

drivers/scsi/libata-scsi.c

@@ -979,6 +979,8 @@ void ata_scsi_badcmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *), u8
 static unsigned int atapi_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
 {
 	struct scsi_cmnd *cmd = qc->scsicmd;
+	struct ata_device *dev = qc->dev;
+	int using_pio = (dev->flags & ATA_DFLAG_PIO);
 
 	qc->tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
 	if (cmd->sc_data_direction == SCSI_DATA_WRITE) {
@@ -992,14 +994,13 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc, u8 *scsicmd)
 	if (cmd->sc_data_direction == SCSI_DATA_NONE)
 		qc->tf.protocol = ATA_PROT_ATAPI;
 
-	/* PIO data xfer - polling */
-	else if ((qc->flags & ATA_QCFLAG_DMA) == 0) {
-		ata_qc_set_polling(qc);
+	/* PIO data xfer */
+	else if (using_pio) {
 		qc->tf.protocol = ATA_PROT_ATAPI;
 		qc->tf.lbam = (8 * 1024) & 0xff;
 		qc->tf.lbah = (8 * 1024) >> 8;
 
-	/* DMA data xfer - interrupt-driven */
+	/* DMA data xfer */
 	} else {
 		qc->tf.protocol = ATA_PROT_ATAPI_DMA;
 		qc->tf.feature |= ATAPI_PKT_DMA;

include/linux/libata.h

@@ -110,7 +110,6 @@ enum {
 	ATA_FLAG_SATA_RESET	= (1 << 7), /* use COMRESET */
 
 	ATA_QCFLAG_ACTIVE	= (1 << 1), /* cmd not yet ack'd to scsi lyer */
-	ATA_QCFLAG_DMA		= (1 << 2), /* data delivered via DMA */
 	ATA_QCFLAG_SG		= (1 << 3), /* have s/g table? */
 	ATA_QCFLAG_SINGLE	= (1 << 4), /* no s/g, just a single buffer */
 	ATA_QCFLAG_DMAMAP	= ATA_QCFLAG_SG | ATA_QCFLAG_SINGLE,
@@ -481,7 +480,6 @@ static inline u8 ata_wait_idle(struct ata_port *ap)
 
 static inline void ata_qc_set_polling(struct ata_queued_cmd *qc)
 {
-	qc->flags &= ~ATA_QCFLAG_DMA;
 	qc->tf.ctl |= ATA_NIEN;
 }