From: Arjan van de Ven <arjan@linux.intel.com>
Subject: [PATCH] libata: Add ALPM power state accounting to the AHCI driver

PowerTOP wants to be able to show the user how effective the ALPM link
power management is for the user. ALPM is worth around 0.5W on a quiet
link; PowerTOP wants to be able to find cases where the "quiet link" isn't
actually quiet.

This patch adds state accounting functionality to the AHCI driver for
PowerTOP to use.
The parts of the patch are
1) the sysfs logic of exposing the stats for each state in sysfs
2) the basic accounting logic that gets update on link change interrupts
   (or when the user accesses the info from sysfs)
3) a "accounting enable" flag; in order to get the accounting to work,
   the driver needs to get phyrdy interrupts on link status changes.
   Normally and currently this is disabled by the driver when ALPM is
   on (to reduce overhead); when PowerTOP is running this will need
   to be on to get usable statistics... hence the sysfs tunable.

The PowerTOP output currently looks like this:

Recent SATA AHCI link activity statistics
Active	Partial	Slumber	Device name
  0.5%	 99.5%	  0.0%	host0

(work to resolve "host0" to a more human readable name is in progress)

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>

---
 drivers/ata/ahci.h    |   15 ++++
 drivers/ata/libahci.c |  187 +++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 200 insertions(+), 2 deletions(-)

Index: linux-2.6.37/drivers/ata/ahci.h
===================================================================
--- linux-2.6.37.orig/drivers/ata/ahci.h
+++ linux-2.6.37/drivers/ata/ahci.h
@@ -262,6 +262,13 @@ struct ahci_em_priv {
 	unsigned long led_state;
 };
 
+enum ahci_port_states {
+	AHCI_PORT_NOLINK = 0,
+	AHCI_PORT_ACTIVE = 1,
+	AHCI_PORT_PARTIAL = 2,
+	AHCI_PORT_SLUMBER = 3
+};
+
 struct ahci_port_priv {
 	struct ata_link		*active_link;
 	struct ahci_cmd_hdr	*cmd_slot;
@@ -280,6 +287,14 @@ struct ahci_port_priv {
 	int			fbs_last_dev;	/* save FBS.DEV of last FIS */
 	/* enclosure management info per PM slot */
 	struct ahci_em_priv	em_priv[EM_MAX_SLOTS];
+
+	/* ALPM accounting state and stats */
+	unsigned int 		accounting_active:1;
+	u64			active_jiffies;
+	u64			partial_jiffies;
+	u64			slumber_jiffies;
+	int			previous_state;
+	int			previous_jiffies;
 };
 
 struct ahci_host_priv {
Index: linux-2.6.37/drivers/ata/libahci.c
===================================================================
--- linux-2.6.37.orig/drivers/ata/libahci.c
+++ linux-2.6.37/drivers/ata/libahci.c
@@ -58,6 +58,17 @@ MODULE_PARM_DESC(ignore_sss, "Ignore sta
 
 static int ahci_set_lpm(struct ata_link *link, enum ata_lpm_policy policy,
 			unsigned hints);
+static ssize_t ahci_alpm_show_active(struct device *dev,
+				  struct device_attribute *attr, char *buf);
+static ssize_t ahci_alpm_show_slumber(struct device *dev,
+				  struct device_attribute *attr, char *buf);
+static ssize_t ahci_alpm_show_partial(struct device *dev,
+				  struct device_attribute *attr, char *buf);
+static ssize_t ahci_alpm_show_accounting(struct device *dev,
+				  struct device_attribute *attr, char *buf);
+static ssize_t ahci_alpm_set_accounting(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count);
 static ssize_t ahci_led_show(struct ata_port *ap, char *buf);
 static ssize_t ahci_led_store(struct ata_port *ap, const char *buf,
 			      size_t size);
@@ -117,6 +128,12 @@ static DEVICE_ATTR(ahci_host_caps, S_IRU
 static DEVICE_ATTR(ahci_host_cap2, S_IRUGO, ahci_show_host_cap2, NULL);
 static DEVICE_ATTR(ahci_host_version, S_IRUGO, ahci_show_host_version, NULL);
 static DEVICE_ATTR(ahci_port_cmd, S_IRUGO, ahci_show_port_cmd, NULL);
+static DEVICE_ATTR(ahci_alpm_active, S_IRUGO, ahci_alpm_show_active, NULL);
+static DEVICE_ATTR(ahci_alpm_partial, S_IRUGO, ahci_alpm_show_partial, NULL);
+static DEVICE_ATTR(ahci_alpm_slumber, S_IRUGO, ahci_alpm_show_slumber, NULL);
+static DEVICE_ATTR(ahci_alpm_accounting, S_IRUGO | S_IWUSR,
+		ahci_alpm_show_accounting, ahci_alpm_set_accounting);
+
 static DEVICE_ATTR(em_buffer, S_IWUSR | S_IRUGO,
 		   ahci_read_em_buffer, ahci_store_em_buffer);
 
@@ -128,6 +145,10 @@ struct device_attribute *ahci_shost_attr
 	&dev_attr_ahci_host_cap2,
 	&dev_attr_ahci_host_version,
 	&dev_attr_ahci_port_cmd,
+	&dev_attr_ahci_alpm_active,
+	&dev_attr_ahci_alpm_partial,
+	&dev_attr_ahci_alpm_slumber,
+	&dev_attr_ahci_alpm_accounting,
 	&dev_attr_em_buffer,
 	NULL
 };
@@ -653,9 +674,14 @@ static int ahci_set_lpm(struct ata_link 
 		 * Disable interrupts on Phy Ready. This keeps us from
 		 * getting woken up due to spurious phy ready
 		 * interrupts.
+		 *
+		 * However, when accounting_active is set, we do want
+		 * the interrupts for accounting purposes.
 		 */
-		pp->intr_mask &= ~PORT_IRQ_PHYRDY;
-		writel(pp->intr_mask, port_mmio + PORT_IRQ_MASK);
+		if (!pp->accounting_active) {
+			pp->intr_mask &= ~PORT_IRQ_PHYRDY;
+			writel(pp->intr_mask, port_mmio + PORT_IRQ_MASK);
+		}
 
 		sata_link_scr_lpm(link, policy, false);
 	}
@@ -1570,6 +1596,162 @@ static void ahci_error_intr(struct ata_p
 		ata_port_abort(ap);
 }
 
+static int get_current_alpm_state(struct ata_port *ap)
+{
+	u32 status = 0;
+
+	ahci_scr_read(&ap->link, SCR_STATUS, &status);
+
+	/* link status is in bits 11-8 */
+	status = status >> 8;
+	status = status & 0x7;
+
+	if (status == 6)
+		return AHCI_PORT_SLUMBER;
+	if (status == 2)
+		return AHCI_PORT_PARTIAL;
+	if (status == 1)
+		return AHCI_PORT_ACTIVE;
+	return AHCI_PORT_NOLINK;
+}
+
+static void account_alpm_stats(struct ata_port *ap)
+{
+	struct ahci_port_priv *pp;
+
+	int new_state;
+	u64 new_jiffies, jiffies_delta;
+
+	if (ap == NULL)
+		return;
+	pp = ap->private_data;
+
+	if (!pp) return;
+
+	new_state = get_current_alpm_state(ap);
+	new_jiffies = jiffies;
+
+	jiffies_delta = new_jiffies - pp->previous_jiffies;
+
+	switch (pp->previous_state) {
+	case AHCI_PORT_NOLINK:
+		pp->active_jiffies = 0;
+		pp->partial_jiffies = 0;
+		pp->slumber_jiffies = 0;
+		break;
+	case AHCI_PORT_ACTIVE:
+		pp->active_jiffies += jiffies_delta;
+		break;
+	case AHCI_PORT_PARTIAL:
+		pp->partial_jiffies += jiffies_delta;
+		break;
+	case AHCI_PORT_SLUMBER:
+		pp->slumber_jiffies += jiffies_delta;
+		break;
+	default:
+		break;
+	}
+	pp->previous_state = new_state;
+	pp->previous_jiffies = new_jiffies;
+}
+
+static ssize_t ahci_alpm_show_active(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	struct ata_port *ap = ata_shost_to_port(shost);
+	struct ahci_port_priv *pp;
+
+	if (!ap || ata_port_is_dummy(ap))
+		return -EINVAL;
+	pp = ap->private_data;
+	account_alpm_stats(ap);
+
+	return sprintf(buf, "%u\n", jiffies_to_msecs(pp->active_jiffies));
+}
+
+static ssize_t ahci_alpm_show_partial(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	struct ata_port *ap = ata_shost_to_port(shost);
+	struct ahci_port_priv *pp;
+
+	if (!ap || ata_port_is_dummy(ap))
+		return -EINVAL;
+
+	pp = ap->private_data;
+	account_alpm_stats(ap);
+
+	return sprintf(buf, "%u\n", jiffies_to_msecs(pp->partial_jiffies));
+}
+
+static ssize_t ahci_alpm_show_slumber(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	struct ata_port *ap = ata_shost_to_port(shost);
+	struct ahci_port_priv *pp;
+
+	if (!ap || ata_port_is_dummy(ap))
+		return -EINVAL;
+
+	pp = ap->private_data;
+
+	account_alpm_stats(ap);
+
+	return sprintf(buf, "%u\n", jiffies_to_msecs(pp->slumber_jiffies));
+}
+
+static ssize_t ahci_alpm_show_accounting(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct Scsi_Host *shost = class_to_shost(dev);
+	struct ata_port *ap = ata_shost_to_port(shost);
+	struct ahci_port_priv *pp;
+
+	if (!ap || ata_port_is_dummy(ap))
+		return -EINVAL;
+
+	pp = ap->private_data;
+
+	return sprintf(buf, "%u\n", pp->accounting_active);
+}
+
+static ssize_t ahci_alpm_set_accounting(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	unsigned long flags;
+	struct Scsi_Host *shost = class_to_shost(dev);
+	struct ata_port *ap = ata_shost_to_port(shost);
+	struct ahci_port_priv *pp;
+	void __iomem *port_mmio;
+
+	if (!ap || ata_port_is_dummy(ap))
+		return 1;
+
+	pp = ap->private_data;
+	port_mmio = ahci_port_base(ap);
+
+	if (!pp)
+		return 1;
+	if (buf[0] == '0')
+		pp->accounting_active = 0;
+	if (buf[0] == '1')
+		pp->accounting_active = 1;
+
+	/* we need to enable the PHYRDY interrupt when we want accounting */
+	if (pp->accounting_active) {
+		spin_lock_irqsave(ap->lock, flags);
+		pp->intr_mask |= PORT_IRQ_PHYRDY;
+		writel(pp->intr_mask, port_mmio + PORT_IRQ_MASK);
+		spin_unlock_irqrestore(ap->lock, flags);
+	}
+	return count;
+}
+
+
 static void ahci_port_intr(struct ata_port *ap)
 {
 	void __iomem *port_mmio = ahci_port_base(ap);
@@ -1590,6 +1772,7 @@ static void ahci_port_intr(struct ata_po
 	/* if LPM is enabled, PHYRDY doesn't mean anything */
 	if (ap->link.lpm_policy > ATA_LPM_MAX_POWER) {
 		status &= ~PORT_IRQ_PHYRDY;
+		account_alpm_stats(ap);
 		ahci_scr_write(&ap->link, SCR_ERROR, SERR_PHYRDY_CHG);
 	}