2 files changed, 42 insertions, 0 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 3c5965d56c47..9fbf0595f3d4 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -2232,6 +2232,40 @@ retry:
         return rc;
 }
 
+static int ata_do_link_spd_horkage(struct ata_device *dev)
+{
+        struct ata_link *plink = ata_dev_phys_link(dev);
+        u32 target, target_limit;
+
+        if (!sata_scr_valid(plink))
+                return 0;
+
+        if (dev->horkage & ATA_HORKAGE_1_5_GBPS)
+                target = 1;
+        else
+                return 0;
+
+        target_limit = (1 << target) - 1;
+
+        /* if already on stricter limit, no need to push further */
+        if (plink->sata_spd_limit <= target_limit)
+                return 0;
+
+        plink->sata_spd_limit = target_limit;
+
+        /* Request another EH round by returning -EAGAIN if link is
+         * going faster than the target speed.  Forward progress is
+         * guaranteed by setting sata_spd_limit to target_limit above.
+         */
+        if (plink->sata_spd > target) {
+                ata_dev_printk(dev, KERN_INFO,
+                               "applying link speed limit horkage to %s\n",
+                               sata_spd_string(target));
+                return -EAGAIN;
+        }
+        return 0;
+}
+
 static inline u8 ata_dev_knobble(struct ata_device *dev)
 {
         struct ata_port *ap = dev->link->ap;
@@ -2322,6 +2356,10 @@ int ata_dev_configure(struct ata_device *dev)
                 return 0;
         }
 
+        rc = ata_do_link_spd_horkage(dev);
+        if (rc)
+                return rc;
+
         /* let ACPI work its magic */
         rc = ata_acpi_on_devcfg(dev);
         if (rc)
@@ -4223,6 +4261,9 @@ static const struct ata_blacklist_entry ata_device_blacklist [] = {
         /* Devices that do not need bridging limits applied */
         { "MTRON MSP-SATA*",            NULL,   ATA_HORKAGE_BRIDGE_OK, },
 
+        /* Devices which aren't very happy with higher link speeds */
+        { "WD My Book",                 NULL,   ATA_HORKAGE_1_5_GBPS, },
+
         /* End Marker */
         { }
 };
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 9dcefee5843c..5d87bc09a1f5 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -380,6 +380,7 @@ enum {
         ATA_HORKAGE_ATAPI_MOD16_DMA = (1 << 11), /* use ATAPI DMA for commands
                                                     not multiple of 16 bytes */
         ATA_HORKAGE_FIRMWARE_WARN = (1 << 12),  /* firwmare update warning */
+        ATA_HORKAGE_1_5_GBPS    = (1 << 13),    /* force 1.5 Gbps */
 
          /* DMA mask for user DMA control: User visible values; DO NOT
             renumber */