[libata] Link power management infrastructure

Device Initiated Power Management, which is defined
in SATA 2.5 can be enabled for disks which support it.
This patch enables DIPM when the user sets the link
power management policy to "min_power".

Additionally, libata drivers can define a function
(enable_pm) that will perform hardware specific actions to
enable whatever power management policy the user set up
for Host Initiated Power management (HIPM).
This power management policy will be activated after all
disks have been enumerated and intialized.  Drivers should
also define disable_pm, which will turn off link power
management, but not change link power management policy.

Documentation/scsi/link_power_management_policy.txt has additional
information.

Signed-off-by:  Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 68 insertions, 0 deletions

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index f752eddc19ed..93bd36c19690 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -110,6 +110,74 @@ static struct scsi_transport_template ata_scsi_transport_template = {
 };
 
 
+static const struct {
+        enum link_pm    value;
+        const char      *name;
+} link_pm_policy[] = {
+        { NOT_AVAILABLE, "max_performance" },
+        { MIN_POWER, "min_power" },
+        { MAX_PERFORMANCE, "max_performance" },
+        { MEDIUM_POWER, "medium_power" },
+};
+
+const char *ata_scsi_lpm_get(enum link_pm policy)
+{
+        int i;
+
+        for (i = 0; i < ARRAY_SIZE(link_pm_policy); i++)
+                if (link_pm_policy[i].value == policy)
+                        return link_pm_policy[i].name;
+
+        return NULL;
+}
+
+static ssize_t ata_scsi_lpm_put(struct class_device *class_dev,
+        const char *buf, size_t count)
+{
+        struct Scsi_Host *shost = class_to_shost(class_dev);
+        struct ata_port *ap = ata_shost_to_port(shost);
+        enum link_pm policy = 0;
+        int i;
+
+        /*
+         * we are skipping array location 0 on purpose - this
+         * is because a value of NOT_AVAILABLE is displayed
+         * to the user as max_performance, but when the user
+         * writes "max_performance", they actually want the
+         * value to match MAX_PERFORMANCE.
+         */
+        for (i = 1; i < ARRAY_SIZE(link_pm_policy); i++) {
+                const int len = strlen(link_pm_policy[i].name);
+                if (strncmp(link_pm_policy[i].name, buf, len) == 0 &&
+                   buf[len] == '\n') {
+                        policy = link_pm_policy[i].value;
+                        break;
+                }
+        }
+        if (!policy)
+                return -EINVAL;
+
+        ata_lpm_schedule(ap, policy);
+        return count;
+}
+
+static ssize_t
+ata_scsi_lpm_show(struct class_device *class_dev, char *buf)
+{
+        struct Scsi_Host *shost = class_to_shost(class_dev);
+        struct ata_port *ap = ata_shost_to_port(shost);
+        const char *policy =
+                ata_scsi_lpm_get(ap->pm_policy);
+
+        if (!policy)
+                return -EINVAL;
+
+        return snprintf(buf, 23, "%s\n", policy);
+}
+CLASS_DEVICE_ATTR(link_power_management_policy, S_IRUGO | S_IWUSR,
+                ata_scsi_lpm_show, ata_scsi_lpm_put);
+EXPORT_SYMBOL_GPL(class_device_attr_link_power_management_policy);
+
 static void ata_scsi_invalid_field(struct scsi_cmnd *cmd,
                                    void (*done)(struct scsi_cmnd *))
 {