libata: Power off empty ports

Give users the option of completely powering off unoccupied
SATA ports using the existing min_power link_power_management_policy
option.  When the use selects this option on an empty port, we
will power the port off by setting DET to off.  For occupied ports,
behavior is unchanged.

Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 76c3c15cb1e6..736bee5dafeb 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3619,8 +3619,14 @@ int sata_link_scr_lpm(struct ata_link *link, enum ata_lpm_policy policy,
                 scontrol |= (0x2 << 8);
                 break;
         case ATA_LPM_MIN_POWER:
-                /* no restrictions on LPM transitions */
-                scontrol &= ~(0x3 << 8);
+                if (ata_link_nr_enabled(link) > 0)
+                        /* no restrictions on LPM transitions */
+                        scontrol &= ~(0x3 << 8);
+                else {
+                        /* empty port, power off */
+                        scontrol &= ~0xf;
+                        scontrol |= (0x1 << 2);
+                }
                 break;
         default:
                 WARN_ON(1);