James Bottomley wrote:

+/* Just quietly quiesce the device and SYNCHRONIZE CACHE for suspend too */
+static int sd_suspend(struct device *dev, pm_message_t state, u32 level)
+{
+	struct scsi_device *sdp = to_scsi_device(dev);
+	struct scsi_disk *sdkp = dev_get_drvdata(dev);
+
+	if (!sdkp)
+		return 0;         /* this can happen */
+
+	if (!sdkp->WCE)
+		return 0;
+
+	/* don't try to sync an offline device ... it will only error */
+	if (!scsi_device_online(sdp))
+		return 0;
+
+	if (sd_sync_cache(sdp))
+		return -EIO;

Add

	if (I_can_PM_this_disk && sd_start_stop_unit(sdp))
		return -EIO;

and libata is happy.

	Jeff