2 files changed, 28 insertions, 7 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 5718c247e23a..c325b7a4246a 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -2389,21 +2389,35 @@ int sata_down_spd_limit(struct ata_port *ap)
 	u32 sstatus, spd, mask;
 	int rc, highbit;
 
+	if (!sata_scr_valid(ap))
+		return -EOPNOTSUPP;
+
+	/* If SCR can be read, use it to determine the current SPD.
+	 * If not, use cached value in ap->sata_spd.
+	 */
 	rc = sata_scr_read(ap, SCR_STATUS, &sstatus);
-	if (rc)
-		return rc;
+	if (rc == 0)
+		spd = (sstatus >> 4) & 0xf;
+	else
+		spd = ap->sata_spd;
 
 	mask = ap->sata_spd_limit;
 	if (mask <= 1)
 		return -EINVAL;
+
+	/* unconditionally mask off the highest bit */
 	highbit = fls(mask) - 1;
 	mask &= ~(1 << highbit);
 
-	spd = (sstatus >> 4) & 0xf;
-	if (spd <= 1)
-		return -EINVAL;
-	spd--;
-	mask &= (1 << spd) - 1;
+	/* Mask off all speeds higher than or equal to the current
+	 * one.  Force 1.5Gbps if current SPD is not available.
+	 */
+	if (spd > 1)
+		mask &= (1 << (spd - 1)) - 1;
+	else
+		mask &= 1;
+
+	/* were we already at the bottom? */
 	if (!mask)
 		return -EINVAL;
 
@@ -5995,6 +6009,7 @@ void ata_dev_init(struct ata_device *dev)
 
 	/* SATA spd limit is bound to the first device */
 	ap->sata_spd_limit = ap->hw_sata_spd_limit;
+	ap->sata_spd = 0;
 
 	/* High bits of dev->flags are used to record warm plug
 	 * requests which occur asynchronously.  Synchronize using
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 19f9947bd96b..183eaf466d4f 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -1799,12 +1799,18 @@ static int ata_eh_reset(struct ata_port *ap, int classify,
 	}
 
 	if (rc == 0) {
+		u32 sstatus;
+
 		/* After the reset, the device state is PIO 0 and the
 		 * controller state is undefined.  Record the mode.
 		 */
 		for (i = 0; i < ATA_MAX_DEVICES; i++)
 			ap->device[i].pio_mode = XFER_PIO_0;
 
+		/* record current link speed */
+		if (sata_scr_read(ap, SCR_STATUS, &sstatus) == 0)
+			ap->sata_spd = (sstatus >> 4) & 0xf;
+
 		if (postreset)
 			postreset(ap, classes);