libata: IORDY handling

I believe this version meets all Sergei's objections

Correct the logic for when we issue a set features for transfer mode

- If the device has IORDY and the controller has IORDY - set the mode
- If the device has IORDY and the controller does not - turn IORDY off
- If neither has IORDY do nothing

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 9b7f3c477730..3dd0e942df36 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4373,7 +4373,14 @@ static unsigned int ata_dev_set_xfermode(struct ata_device *dev)
         tf.feature = SETFEATURES_XFER;
         tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE | ATA_TFLAG_POLLING;
         tf.protocol = ATA_PROT_NODATA;
-        tf.nsect = dev->xfer_mode;
+        /* If we are using IORDY we must send the mode setting command */
+        if (ata_pio_need_iordy(dev))
+                tf.nsect = dev->xfer_mode;
+        /* If the device has IORDY and the controller does not - turn it off */
+        else if (ata_id_has_iordy(dev->id))
+                tf.nsect = 0x01;
+        else /* In the ancient relic department - skip all of this */
+                return 0;
 
         err_mask = ata_exec_internal(dev, &tf, NULL, DMA_NONE, NULL, 0, 0);