3 files changed, 29 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);
 
diff --git a/include/linux/libata.h b/include/linux/libata.h
index c732b3e78e28..16ebdf152c75 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -531,6 +531,7 @@ struct ata_port {
         unsigned int            cbl;    /* cable type; ATA_CBL_xxx */
         unsigned int            hw_sata_spd_limit;
         unsigned int            sata_spd_limit; /* SATA PHY speed limit */
+        unsigned int            sata_spd;       /* current SATA PHY speed */
 
         /* record runtime error info, protected by host lock */
         struct ata_eh_info      eh_info;