allow user to power off unused ports via sysfs

Index: linux-ahci-phy/drivers/ata/libata-core.c
===================================================================
@@ -162,6 +162,19 @@ MODULE_DESCRIPTION("Library module for A
 MODULE_LICENSE("GPL");
 MODULE_VERSION(DRV_VERSION);
 
+static void ata_phy_offline(struct ata_link *link)
+{
+	u32 scontrol;
+	int rc;
+
+	/* set DET to 4 */
+	rc = sata_scr_read(link, SCR_CONTROL, &scontrol);
+	if (rc)
+		return;
+	scontrol &= ~0xf;
+	scontrol |= (1 << 2);
+	sata_scr_write(link, SCR_CONTROL, scontrol);
+}
 
 /**
  *	ata_force_cbl - force cable type according to libata.force

@@ -953,6 +966,7 @@ static int ata_dev_set_dipm(struct ata_d
 		 * disallow all transitions which effectively
 		 * disable DIPM anyway.
 		 */
+	default:
 		break;
 	}
 

@@ -980,6 +994,22 @@ void ata_dev_enable_pm(struct ata_device
 	int rc = 0;
 	struct ata_port *ap = dev->link->ap;
 
+	/*
+	 * if we don't have a device attached, all we can
+	 * do is power off
+	 */
+	if (!ata_dev_enabled(dev) && policy == POWER_OFF) {
+		ap->flags |= ATA_FLAG_NO_HOTPLUG;
+		ata_phy_offline(&ap->link);
+		goto enable_pm_out;
+	}
+
+	/*
+         * if there's no device attached, we are done
+	 */
+	if (!ata_dev_enabled(dev))
+		return;
+
 	/* set HIPM first, then DIPM */
 	if (ap->ops->enable_pm)
 		rc = ap->ops->enable_pm(ap, policy);

@@ -1020,10 +1050,24 @@ static void ata_dev_disable_pm(struct at
 
 void ata_lpm_schedule(struct ata_port *ap, enum link_pm policy)
 {
-	ap->pm_policy = policy;
 	ap->link.eh_info.action |= ATA_EH_LPM;
+
+	/*
+	 * if we are coming from a state of OFF to ON, we need
+	 * to reset the link and scan for devices in case someone
+	 * plugged something in while we were off.
+	 * Clear the NO_HOTPLUG flag because we are leaving the
+	 * phy on now.
+	 */
+	if (ap->pm_policy == POWER_OFF && policy != POWER_OFF) {
+		ap->flags &= ~ATA_FLAG_NO_HOTPLUG;
+		ap->link.eh_info.probe_mask |= ATA_ALL_DEVICES;
+		ap->link.eh_info.flags |= ATA_EH_RESET;
+	}
 	ap->link.eh_info.flags |= ATA_EHI_NO_AUTOPSY;
+	ap->pm_policy = policy;
 	ata_port_schedule_eh(ap);
+	ata_port_wait_eh(ap);
 }
 
 #ifdef CONFIG_PM

@@ -2678,6 +2722,7 @@ void ata_port_disable(struct ata_port *a
 	ap->link.device[0].class = ATA_DEV_NONE;
 	ap->link.device[1].class = ATA_DEV_NONE;
 	ap->flags |= ATA_FLAG_DISABLED;
+	ata_phy_offline(&ap->link);
 }
 
 /**

@@ -5614,6 +5659,8 @@ int ata_host_register(struct ata_host *h
 		if (ap->ops->error_handler) {
 			struct ata_eh_info *ehi = &ap->link.eh_info;
 			unsigned long flags;
+			int device_attached = 0;
+			struct ata_device *dev;
 
 			ata_port_probe(ap);
 

@@ -5632,6 +5679,15 @@ int ata_host_register(struct ata_host *h
 
 			/* wait for EH to finish */
 			ata_port_wait_eh(ap);
+			ata_link_for_each_dev(dev, &ap->link)
+				if (ata_dev_enabled(dev))
+					device_attached++;
+			if (!device_attached &&
+			    (ap->flags & ATA_FLAG_NO_HOTPLUG)) {
+				/* no device present, disable port */
+				ap->pm_policy = POWER_OFF;
+				ata_port_disable(ap);
+			}
 		} else {
 			DPRINTK("ata%u: bus probe begin\n", ap->print_id);
 			rc = ata_bus_probe(ap);

Index: linux-ahci-phy/include/linux/libata.h
===================================================================
@@ -190,6 +190,7 @@ enum {
 	ATA_FLAG_AN		= (1 << 18), /* controller supports AN */
 	ATA_FLAG_PMP		= (1 << 19), /* controller supports PMP */
 	ATA_FLAG_IPM		= (1 << 20), /* driver can handle IPM */
+	ATA_FLAG_NO_HOTPLUG	= (1 << 21), /* port doesn't support HP */
 
 	/* The following flag belongs to ap->pflags but is kept in
 	 * ap->flags because it's referenced in many LLDs and will be

@@ -439,6 +440,7 @@ enum link_pm {
 	MIN_POWER,
 	MAX_PERFORMANCE,
 	MEDIUM_POWER,
+	POWER_OFF,
 };
 extern struct device_attribute dev_attr_link_power_management_policy;
 

Index: linux-ahci-phy/drivers/ata/libata-scsi.c
===================================================================
@@ -122,6 +122,7 @@ static const struct {
 	{ MIN_POWER, "min_power" },
 	{ MAX_PERFORMANCE, "max_performance" },
 	{ MEDIUM_POWER, "medium_power" },
+	{ POWER_OFF, "power_off" },
 };
 
 static const char *ata_scsi_lpm_get(enum link_pm policy)

Index: linux-ahci-phy/drivers/ata/ahci.c
===================================================================
@@ -53,9 +53,13 @@ static int ahci_skip_host_reset;
 module_param_named(skip_host_reset, ahci_skip_host_reset, int, 0444);
 MODULE_PARM_DESC(skip_host_reset, "skip global host reset (0=don't skip, 1=skip)");
 
+static int ahci_power_save = 1;
+module_param_named(power_save, ahci_power_save, int, 0444);
+MODULE_PARM_DESC(power_save, "Power off unused ports (0=don't power off, 1=power off)");
 static int ahci_enable_alpm(struct ata_port *ap,
 		enum link_pm policy);
 static void ahci_disable_alpm(struct ata_port *ap);
+static int ahci_is_hotplug_capable(struct ata_port *ap);
 
 enum {
 	AHCI_PCI_BAR		= 5,

@@ -168,6 +172,8 @@ enum {
 	PORT_CMD_ASP		= (1 << 27), /* Aggressive Slumber/Partial */
 	PORT_CMD_ALPE		= (1 << 26), /* Aggressive Link PM enable */
 	PORT_CMD_ATAPI		= (1 << 24), /* Device is ATAPI */
+	PORT_CMD_ESP		= (1 << 21), /* External SATA Port */
+	PORT_CMD_HPCP		= (1 << 18), /* port is hot plug capable */
 	PORT_CMD_PMP		= (1 << 17), /* PMP attached */
 	PORT_CMD_LIST_ON	= (1 << 15), /* cmd list DMA engine running */
 	PORT_CMD_FIS_ON		= (1 << 14), /* FIS DMA engine running */

@@ -1998,6 +2004,18 @@ static int ahci_pci_device_resume(struct
 }
 #endif
 
+static int ahci_is_hotplug_capable(struct ata_port *ap)
+{
+	void __iomem *port_mmio = ahci_port_base(ap);
+	u8 cmd;
+
+	if (!ahci_power_save)
+		return 1;
+
+	cmd = readl(port_mmio + PORT_CMD);
+	return ((cmd & PORT_CMD_HPCP) || (cmd & PORT_CMD_ESP));
+}
+
 static int ahci_port_start(struct ata_port *ap)
 {
 	struct device *dev = ap->host->dev;

@@ -2049,6 +2067,9 @@ static int ahci_port_start(struct ata_po
 
 	ap->private_data = pp;
 
+	/* set some flags based on port capabilities */
+	if (!ahci_is_hotplug_capable(ap))
+		ap->flags |= ATA_FLAG_NO_HOTPLUG;
 	/* engage engines, captain */
 	return ahci_port_resume(ap);
 }