1 files changed, 25 insertions, 0 deletions

diff --git a/drivers/ata/ata_piix.c b/drivers/ata/ata_piix.c
index ea2c7649d399..a9027b8fbdd5 100644
--- a/drivers/ata/ata_piix.c
+++ b/drivers/ata/ata_piix.c
@@ -1348,6 +1348,8 @@ static void __devinit piix_init_sidpr(struct ata_host *host)
 {
         struct pci_dev *pdev = to_pci_dev(host->dev);
         struct piix_host_priv *hpriv = host->private_data;
+        struct ata_device *dev0 = &host->ports[0]->link.device[0];
+        u32 scontrol;
         int i;
 
         /* check for availability */
@@ -1366,6 +1368,29 @@ static void __devinit piix_init_sidpr(struct ata_host *host)
                 return;
 
         hpriv->sidpr = pcim_iomap_table(pdev)[PIIX_SIDPR_BAR];
+
+        /* SCR access via SIDPR doesn't work on some configurations.
+         * Give it a test drive by inhibiting power save modes which
+         * we'll do anyway.
+         */
+        scontrol = piix_sidpr_read(dev0, SCR_CONTROL);
+
+        /* if IPM is already 3, SCR access is probably working.  Don't
+         * un-inhibit power save modes as BIOS might have inhibited
+         * them for a reason.
+         */
+        if ((scontrol & 0xf00) != 0x300) {
+                scontrol |= 0x300;
+                piix_sidpr_write(dev0, SCR_CONTROL, scontrol);
+                scontrol = piix_sidpr_read(dev0, SCR_CONTROL);
+
+                if ((scontrol & 0xf00) != 0x300) {
+                        dev_printk(KERN_INFO, host->dev, "SCR access via "
+                                   "SIDPR is available but doesn't work\n");
+                        return;
+                }
+        }
+
         host->ports[0]->ops = &piix_sidpr_sata_ops;
         host->ports[1]->ops = &piix_sidpr_sata_ops;
 }