1 files changed, 27 insertions, 0 deletions

diff --git a/drivers/ata/sata_via.c b/drivers/ata/sata_via.c
index 101d8c219caf..4730c42a5ee5 100644
--- a/drivers/ata/sata_via.c
+++ b/drivers/ata/sata_via.c
@@ -575,6 +575,33 @@ static void svia_configure(struct pci_dev *pdev)
                 tmp8 |= NATIVE_MODE_ALL;
                 pci_write_config_byte(pdev, SATA_NATIVE_MODE, tmp8);
         }
+
+        /*
+         * vt6421 has problems talking to some drives.  The following
+         * is the fix from Joseph Chan <JosephChan@via.com.tw>.
+         *
+         * When host issues HOLD, device may send up to 20DW of data
+         * before acknowledging it with HOLDA and the host should be
+         * able to buffer them in FIFO.  Unfortunately, some WD drives
+         * send upto 40DW before acknowledging HOLD and, in the
+         * default configuration, this ends up overflowing vt6421's
+         * FIFO, making the controller abort the transaction with
+         * R_ERR.
+         *
+         * Rx52[2] is the internal 128DW FIFO Flow control watermark
+         * adjusting mechanism enable bit and the default value 0
+         * means host will issue HOLD to device when the left FIFO
+         * size goes below 32DW.  Setting it to 1 makes the watermark
+         * 64DW.
+         *
+         * https://bugzilla.kernel.org/show_bug.cgi?id=15173
+         * http://article.gmane.org/gmane.linux.ide/46352
+         */
+        if (pdev->device == 0x3249) {
+                pci_read_config_byte(pdev, 0x52, &tmp8);
+                tmp8 |= 1 << 2;
+                pci_write_config_byte(pdev, 0x52, tmp8);
+        }
 }
 
 static int svia_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)