[PATCH] libata: implement PM EH actions

Implement two PM per-dev EH actions - ATA_EH_SUSPEND and
ATA_EH_RESUME. Each action puts the target device into suspended mode
and resumes from it respectively.

Once a device is put to suspended mode, no EH operations other than
RESUME is allowed on the device. The device will stay suspended till
it gets resumed and thus reset and revalidated. To implement this, a
new device state helper - ata_dev_ready() - is implemented and used in
EH action implementations to make them operate only on attached &
running devices.

If all possible devices on a port are suspended, reset is skipped too.
This prevents spurious events including hotplug events from disrupting
suspended devices.

Signed-off-by: Tejun Heo <[e-mail]>
Signed-off-by: Jeff Garzik <[e-mail]>

drivers/scsi/libata-core.c

···
 		 * return error code and failing device on failure.
 		 */
 		for (i = 0; i < ATA_MAX_DEVICES; i++) {
-			if (ata_dev_enabled(&ap->device[i])) {
+			if (ata_dev_ready(&ap->device[i])) {
 				ap->ops->set_mode(ap);
 				break;
 			}
···
 	for (i = 0; i < ATA_MAX_DEVICES; i++) {
 		dev = &ap->device[i];
 
-		if (!ata_dev_enabled(dev))
+		/* don't udpate suspended devices' xfer mode */
+		if (!ata_dev_ready(dev))
 			continue;
 
 		rc = ata_dev_set_mode(dev);

drivers/scsi/libata-eh.c

···
 		dev = &ap->device[i];
 		action = ata_eh_dev_action(dev);
 
-		if (action & ATA_EH_REVALIDATE && ata_dev_enabled(dev)) {
+		if (action & ATA_EH_REVALIDATE && ata_dev_ready(dev)) {
 			if (ata_port_offline(ap)) {
 				rc = -EIO;
 				break;
···
 	return rc;
 }
 
+/**
+ *	ata_eh_suspend - handle suspend EH action
+ *	@ap: target host port
+ *	@r_failed_dev: result parameter to indicate failing device
+ *
+ *	Handle suspend EH action.  Disk devices are spinned down and
+ *	other types of devices are just marked suspended.  Once
+ *	suspended, no EH action to the device is allowed until it is
+ *	resumed.
+ *
+ *	LOCKING:
+ *	Kernel thread context (may sleep).
+ *
+ *	RETURNS:
+ *	0 on success, -errno otherwise
+ */
+static int ata_eh_suspend(struct ata_port *ap, struct ata_device **r_failed_dev)
+{
+	struct ata_device *dev;
+	int i, rc = 0;
+
+	DPRINTK("ENTER\n");
+
+	for (i = 0; i < ATA_MAX_DEVICES; i++) {
+		unsigned long flags;
+		unsigned int action, err_mask;
+
+		dev = &ap->device[i];
+		action = ata_eh_dev_action(dev);
+
+		if (!ata_dev_enabled(dev) || !(action & ATA_EH_SUSPEND))
+			continue;
+
+		WARN_ON(dev->flags & ATA_DFLAG_SUSPENDED);
+
+		ata_eh_about_to_do(ap, dev, ATA_EH_SUSPEND);
+
+		if (dev->class == ATA_DEV_ATA && !(action & ATA_EH_PM_FREEZE)) {
+			/* flush cache */
+			rc = ata_flush_cache(dev);
+			if (rc)
+				break;
+
+			/* spin down */
+			err_mask = ata_do_simple_cmd(dev, ATA_CMD_STANDBYNOW1);
+			if (err_mask) {
+				ata_dev_printk(dev, KERN_ERR, "failed to "
+					       "spin down (err_mask=0x%x)\n",
+					       err_mask);
+				rc = -EIO;
+				break;
+			}
+		}
+
+		spin_lock_irqsave(ap->lock, flags);
+		dev->flags |= ATA_DFLAG_SUSPENDED;
+		spin_unlock_irqrestore(ap->lock, flags);
+
+		ata_eh_done(ap, dev, ATA_EH_SUSPEND);
+	}
+
+	if (rc)
+		*r_failed_dev = dev;
+
+	DPRINTK("EXIT\n");
+	return 0;
+}
+
+/**
+ *	ata_eh_prep_resume - prep for resume EH action
+ *	@ap: target host port
+ *
+ *	Clear SUSPENDED in preparation for scheduled resume actions.
+ *	This allows other parts of EH to access the devices being
+ *	resumed.
+ *
+ *	LOCKING:
+ *	Kernel thread context (may sleep).
+ */
+static void ata_eh_prep_resume(struct ata_port *ap)
+{
+	struct ata_device *dev;
+	unsigned long flags;
+	int i;
+
+	DPRINTK("ENTER\n");
+
+	for (i = 0; i < ATA_MAX_DEVICES; i++) {
+		unsigned int action;
+
+		dev = &ap->device[i];
+		action = ata_eh_dev_action(dev);
+
+		if (!ata_dev_enabled(dev) || !(action & ATA_EH_RESUME))
+			continue;
+
+		spin_lock_irqsave(ap->lock, flags);
+		dev->flags &= ~ATA_DFLAG_SUSPENDED;
+		spin_unlock_irqrestore(ap->lock, flags);
+	}
+
+	DPRINTK("EXIT\n");
+}
+
+/**
+ *	ata_eh_resume - handle resume EH action
+ *	@ap: target host port
+ *	@r_failed_dev: result parameter to indicate failing device
+ *
+ *	Handle resume EH action.  Target devices are already reset and
+ *	revalidated.  Spinning up is the only operation left.
+ *
+ *	LOCKING:
+ *	Kernel thread context (may sleep).
+ *
+ *	RETURNS:
+ *	0 on success, -errno otherwise
+ */
+static int ata_eh_resume(struct ata_port *ap, struct ata_device **r_failed_dev)
+{
+	struct ata_device *dev;
+	int i, rc = 0;
+
+	DPRINTK("ENTER\n");
+
+	for (i = 0; i < ATA_MAX_DEVICES; i++) {
+		unsigned int action, err_mask;
+
+		dev = &ap->device[i];
+		action = ata_eh_dev_action(dev);
+
+		if (!ata_dev_enabled(dev) || !(action & ATA_EH_RESUME))
+			continue;
+
+		ata_eh_about_to_do(ap, dev, ATA_EH_RESUME);
+
+		if (dev->class == ATA_DEV_ATA && !(action & ATA_EH_PM_FREEZE)) {
+			err_mask = ata_do_simple_cmd(dev,
+						     ATA_CMD_IDLEIMMEDIATE);
+			if (err_mask) {
+				ata_dev_printk(dev, KERN_ERR, "failed to "
+					       "spin up (err_mask=0x%x)\n",
+					       err_mask);
+				rc = -EIO;
+				break;
+			}
+		}
+
+		ata_eh_done(ap, dev, ATA_EH_RESUME);
+	}
+
+	if (rc)
+		*r_failed_dev = dev;
+
+	DPRINTK("EXIT\n");
+	return 0;
+}
+
 static int ata_port_nr_enabled(struct ata_port *ap)
 {
 	int i, cnt = 0;
···
 	struct ata_eh_context *ehc = &ap->eh_context;
 	int i;
 
+	/* skip if all possible devices are suspended */
+	for (i = 0; i < ata_port_max_devices(ap); i++) {
+		struct ata_device *dev = &ap->device[i];
+
+		if (ata_dev_absent(dev) || ata_dev_ready(dev))
+			break;
+	}
+
+	if (i == ata_port_max_devices(ap))
+		return 1;
+
+	/* always thaw frozen port and recover failed devices */
 	if (ap->pflags & ATA_PFLAG_FROZEN || ata_port_nr_enabled(ap))
 		return 0;
 
···
 	if (ap->pflags & ATA_PFLAG_UNLOADING)
 		goto out;
 
+	/* prep for resume */
+	ata_eh_prep_resume(ap);
+
 	/* skip EH if possible. */
 	if (ata_eh_skip_recovery(ap))
 		ehc->i.action = 0;
···
 	if (rc)
 		goto dev_fail;
 
+	/* resume devices */
+	rc = ata_eh_resume(ap, &dev);
+	if (rc)
+		goto dev_fail;
+
 	/* configure transfer mode if the port has been reset */
 	if (ehc->i.flags & ATA_EHI_DID_RESET) {
 		rc = ata_set_mode(ap, &dev);
···
 			goto dev_fail;
 		}
 	}
+
+	/* suspend devices */
+	rc = ata_eh_suspend(ap, &dev);
+	if (rc)
+		goto dev_fail;
 
 	goto out;
 

include/linux/libata.h

···
 	ATA_DFLAG_CFG_MASK	= (1 << 8) - 1,
 
 	ATA_DFLAG_PIO		= (1 << 8), /* device currently in PIO mode */
+	ATA_DFLAG_SUSPENDED	= (1 << 9), /* device suspended */
 	ATA_DFLAG_INIT_MASK	= (1 << 16) - 1,
 
 	ATA_DFLAG_DETACH	= (1 << 16),
···
 	ATA_EH_REVALIDATE	= (1 << 0),
 	ATA_EH_SOFTRESET	= (1 << 1),
 	ATA_EH_HARDRESET	= (1 << 2),
+	ATA_EH_SUSPEND		= (1 << 3),
+	ATA_EH_RESUME		= (1 << 4),
+	ATA_EH_PM_FREEZE	= (1 << 5),
 
 	ATA_EH_RESET_MASK	= ATA_EH_SOFTRESET | ATA_EH_HARDRESET,
-	ATA_EH_PERDEV_MASK	= ATA_EH_REVALIDATE,
+	ATA_EH_PERDEV_MASK	= ATA_EH_REVALIDATE | ATA_EH_SUSPEND |
+				  ATA_EH_RESUME | ATA_EH_PM_FREEZE,
 
 	/* ata_eh_info->flags */
 	ATA_EHI_HOTPLUGGED	= (1 << 0),  /* could have been hotplugged */
···
 static inline unsigned int ata_dev_absent(const struct ata_device *dev)
 {
 	return ata_class_absent(dev->class);
+}
+
+static inline unsigned int ata_dev_ready(const struct ata_device *dev)
+{
+	return ata_dev_enabled(dev) && !(dev->flags & ATA_DFLAG_SUSPENDED);
 }
 
 /*