[patch 1/2] allow user to power off unused ports via sysfs

[kristen.c.accardi@intel.com]

This patch expands the definition of link power management to 
include the notion of simply powering the entire port off.  
We add a new valid value for link_power_management_policy:

power_off:  phy is not on at all.
min_power:  driver uses minimum possible power. hotplug
            may or may not be available.
medium_power: best power/performance tradeoff.  hotplug
            may or may not be available
max_performance: max performance without regard to power
            hot plug is available.

Additionally - this patch modifies the libata-core to
power off the port automatically at init time if the
driver marks the port as not hotpluggable.

The user may not power off a port if it is occupied.
If the port is powered off, and a new drive is plugged
in, the drive will not be detected until the port is
powered back up by setting the link_power_management_policy
to "max_performance".

Signed-off-by:  Kristen Carlson Accardi <kristen.c.accardi@intel.com>
---
 drivers/ata/libata-core.c |   58 +++++++++++++++++++++++++++++++++++++++++++++-
 drivers/ata/libata-scsi.c |    1 
 include/linux/libata.h    |    2 +
 3 files changed, 60 insertions(+), 1 deletion(-)

Index: linux-ahci-phy/drivers/ata/libata-core.c
===================================================================
--- linux-ahci-phy.orig/drivers/ata/libata-core.c	2008-06-27 13:32:51.000000000 -0700
+++ linux-ahci-phy/drivers/ata/libata-core.c	2008-07-01 16:33:00.000000000 -0700
@@ -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
===================================================================
--- linux-ahci-phy.orig/include/linux/libata.h	2008-06-27 13:32:57.000000000 -0700
+++ linux-ahci-phy/include/linux/libata.h	2008-06-27 13:38:11.000000000 -0700
@@ -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
===================================================================
--- linux-ahci-phy.orig/drivers/ata/libata-scsi.c	2008-06-27 13:32:51.000000000 -0700
+++ linux-ahci-phy/drivers/ata/libata-scsi.c	2008-06-27 13:38:11.000000000 -0700
@@ -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)

--