libata: automatically use DMADIR if drive/bridge requires it

Back in 2.6.17-rc2, a libata module parameter was added for atapi_dmadir.

That's nice, but most SATA devices which need it will tell us about it
in their IDENTIFY PACKET response, as bit-15 of word-62 of the
returned data (as per ATA7, ATA8 specifications).

So for those which specify it, we should automatically use the DMADIR bit.
Otherwise, disc writing will fail by default on many SATA-ATAPI drives.

This patch adds ATA_DFLAG_DMADIR and make ata_dev_configure() set it
if atapi_dmadir is set or identify data indicates DMADIR is necessary.
atapi_xlat() is converted to check ATA_DFLAG_DMADIR before setting
DMADIR.

Original patch is from Mark Lord.

Signed-off-by: Tejun Heo <[e-mail]>
Cc: Mark Lord <[e-mail]>
Signed-off-by: Jeff Garzik <[e-mail]>

drivers/ata/libata-core.c

···
 	else if (dev->class == ATA_DEV_ATAPI) {
 		const char *cdb_intr_string = "";
 		const char *atapi_an_string = "";
+		const char *dma_dir_string = "";
 		u32 sntf;
 
 		rc = atapi_cdb_len(id);
···
 			cdb_intr_string = ", CDB intr";
 		}
 
+		if (atapi_dmadir || atapi_id_dmadir(dev->id)) {
+			dev->flags |= ATA_DFLAG_DMADIR;
+			dma_dir_string = ", DMADIR";
+		}
+
 		/* print device info to dmesg */
 		if (ata_msg_drv(ap) && print_info)
 			ata_dev_printk(dev, KERN_INFO,
-				       "ATAPI: %s, %s, max %s%s%s\n",
+				       "ATAPI: %s, %s, max %s%s%s%s\n",
 				       modelbuf, fwrevbuf,
 				       ata_mode_string(xfer_mask),
-				       cdb_intr_string, atapi_an_string);
+				       cdb_intr_string, atapi_an_string,
+				       dma_dir_string);
 	}
 
 	/* determine max_sectors */

drivers/ata/libata-scsi.c

···
 		qc->tf.protocol = ATAPI_PROT_DMA;
 		qc->tf.feature |= ATAPI_PKT_DMA;
 
-		if (atapi_dmadir && (scmd->sc_data_direction != DMA_TO_DEVICE))
+		if ((dev->flags & ATA_DFLAG_DMADIR) &&
+		    (scmd->sc_data_direction != DMA_TO_DEVICE))
 			/* some SATA bridges need us to indicate data xfer direction */
 			qc->tf.feature |= ATAPI_DMADIR;
 	}

include/linux/ata.h

···
 	return (dev_id[0] >> 8) & 0x1f;
 }
 
+static inline int atapi_id_dmadir(const u16 *dev_id)
+{
+	return ata_id_major_version(dev_id) >= 7 && (dev_id[62] & 0x8000);
+}
+
 static inline int is_multi_taskfile(struct ata_taskfile *tf)
 {
 	return (tf->command == ATA_CMD_READ_MULTI) ||

include/linux/libata.h

···
 	ATA_DFLAG_AN		= (1 << 7), /* AN configured */
 	ATA_DFLAG_HIPM		= (1 << 8), /* device supports HIPM */
 	ATA_DFLAG_DIPM		= (1 << 9), /* device supports DIPM */
+	ATA_DFLAG_DMADIR	= (1 << 10), /* device requires DMADIR */
 	ATA_DFLAG_CFG_MASK	= (1 << 12) - 1,
 
 	ATA_DFLAG_PIO		= (1 << 12), /* device limited to PIO mode */