[libata] fix PIO data xfer on big endian

We were reading the data swapped, which was correct for the
data page read from IDENTIFY DEVICE and incorrect for all other
situations.

Noticed by Ben Herrenschmidt.

drivers/scsi/libata-core.c

@@ -43,6 +43,7 @@
 #include <linux/libata.h>
 #include <asm/io.h>
 #include <asm/semaphore.h>
+#include <asm/byteorder.h>
 
 #include "libata.h"
 
@@ -58,6 +59,7 @@ static int ata_choose_xfer_mode(struct ata_port *ap,
 				u8 *xfer_mode_out,
 				unsigned int *xfer_shift_out);
 static int ata_qc_complete_noop(struct ata_queued_cmd *qc, u8 drv_stat);
+static void swap_buf_le16(u16 *buf, unsigned int buf_words);
 
 static unsigned int ata_unique_id = 1;
 static struct workqueue_struct *ata_wq;
@@ -1032,6 +1034,8 @@ static void ata_dev_identify(struct ata_port *ap, unsigned int device)
 		goto err_out;
 	}
 
+	swap_buf_le16(dev->id, ATA_ID_WORDS);
+
 	/* print device capabilities */
 	printk(KERN_DEBUG "ata%u: dev %u cfg "
 	       "49:%04x 82:%04x 83:%04x 84:%04x 85:%04x 86:%04x 87:%04x 88:%04x\n",
@@ -2062,6 +2066,16 @@ static void ata_pio_complete (struct ata_port *ap)
 	ata_qc_complete(qc, drv_stat);
 }
 
+static void swap_buf_le16(u16 *buf, unsigned int buf_words)
+{
+#ifdef __BIG_ENDIAN
+	unsigned int i;
+
+	for (i = 0; i < words; i++)
+		buf[i] = le16_to_cpu(buf[i]);
+#endif /* __BIG_ENDIAN */
+}
+
 static void ata_mmio_data_xfer(struct ata_port *ap, unsigned char *buf,
 			       unsigned int buflen, int write_data)
 {
@@ -2072,22 +2086,22 @@ static void ata_mmio_data_xfer(struct ata_port *ap, unsigned char *buf,
 
 	if (write_data) {
 		for (i = 0; i < words; i++)
-			writew(buf16[i], mmio);
+			writew(le16_to_cpu(buf16[i]), mmio);
 	} else {
 		for (i = 0; i < words; i++)
-			buf16[i] = readw(mmio);
+			buf16[i] = cpu_to_le16(readw(mmio));
 	}
 }
 
 static void ata_pio_data_xfer(struct ata_port *ap, unsigned char *buf,
 			      unsigned int buflen, int write_data)
 {
-	unsigned int dwords = buflen >> 2;
+	unsigned int dwords = buflen >> 1;
 
 	if (write_data)
-		outsl(ap->ioaddr.data_addr, buf, dwords);
+		outsw(ap->ioaddr.data_addr, buf, dwords);
 	else
-		insl(ap->ioaddr.data_addr, buf, dwords);
+		insw(ap->ioaddr.data_addr, buf, dwords);
 }
 
 static void ata_data_xfer(struct ata_port *ap, unsigned char *buf,