libata: clear TF before IDENTIFYing

[powerpc.git] / drivers / ata / libata-core.c

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 25d8d3f..2cf8251 100644 (file)
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -1410,7 +1410,16 @@ int ata_dev_read_id(struct ata_device *dev, unsigned int *p_class,
        }
 
        tf.protocol = ATA_PROT_PIO;
-       tf.flags |= ATA_TFLAG_POLLING; /* for polling presence detection */
+
+       /* Some devices choke if TF registers contain garbage.  Make
+        * sure those are properly initialized.
+        */
+       tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
+
+       /* Device presence detection is unreliable on some
+        * controllers.  Always poll IDENTIFY if available.
+        */
+       tf.flags |= ATA_TFLAG_POLLING;
 
        err_mask = ata_exec_internal(dev, &tf, NULL, DMA_FROM_DEVICE,
                                     id, sizeof(id[0]) * ATA_ID_WORDS);