prep for PMP support, take 3

index 0c94b65..d7b28f6 100644
@@ -2169,7 +2169,7 @@ static int ata_dev_set_mode(struct ata_d
 		return -EIO;
 	}
 
-	rc = ata_dev_revalidate(dev, 0);
+	rc = ata_dev_revalidate(dev, ATA_DEV_UNKNOWN, 0);
 	if (rc)
 		return rc;
 

@@ -3073,6 +3073,7 @@ static int ata_dev_same_device(struct at
 /**
  *	ata_dev_revalidate - Revalidate ATA device
  *	@dev: device to revalidate
+ *	@new_class: new class code
  *	@post_reset: is this revalidation after reset?
  *
  *	Re-read IDENTIFY page and make sure @dev is still attached to

@@ -3084,9 +3085,9 @@ static int ata_dev_same_device(struct at
  *	RETURNS:
  *	0 on success, negative errno otherwise
  */
-int ata_dev_revalidate(struct ata_device *dev, int post_reset)
+int ata_dev_revalidate(struct ata_device *dev, unsigned int new_class,
+		       int post_reset)
 {
-	unsigned int class = dev->class;
 	u16 *id = (void *)dev->link->ap->sector_buf;
 	int rc;
 

@@ -3095,13 +3096,22 @@ int ata_dev_revalidate(struct ata_device
 		goto fail;
 	}
 
+	if (ata_class_enabled(new_class)) {
+		/* sometimes wrong class is reported, let it retry */
+		if (new_class != ATA_DEV_ATA && new_class != ATA_DEV_ATAPI) {
+			rc = -EIO;
+			goto fail;
+		}
+	} else
+		new_class = dev->class;
+
 	/* read ID data */
-	rc = ata_dev_read_id(dev, &class, post_reset, id);
+	rc = ata_dev_read_id(dev, &new_class, post_reset, id);
 	if (rc)
 		goto fail;
 
 	/* is the device still there? */
-	if (!ata_dev_same_device(dev, class, id)) {
+	if (!ata_dev_same_device(dev, new_class, id)) {
 		rc = -ENODEV;
 		goto fail;
 	}

index ead460b..8ee4674 100644
@@ -1738,7 +1738,7 @@ static int ata_eh_revalidate_and_attach(
 			}
 
 			ata_eh_about_to_do(link, dev, ATA_EH_REVALIDATE);
-			rc = ata_dev_revalidate(dev,
+			rc = ata_dev_revalidate(dev, ehc->classes[dev->devno],
 					ehc->i.flags & ATA_EHI_DID_RESET);
 			if (rc)
 				break;

index e09dfe6..676e1d9 100644
@@ -729,7 +729,8 @@ extern int sata_std_hardreset(struct ata
 extern void ata_std_postreset(struct ata_link *link, unsigned int *classes);
 extern void sata_std_hp_poll_activate(struct ata_port *ap);
 extern int sata_std_hp_poll(struct ata_port *ap);
-extern int ata_dev_revalidate(struct ata_device *dev, int post_reset);
+extern int ata_dev_revalidate(struct ata_device *dev, unsigned int new_class,
+			      int post_reset);
 extern void ata_port_disable(struct ata_port *);
 extern void ata_std_ports(struct ata_ioports *ioaddr);
 #ifdef CONFIG_PCI

index d7b28f6..0dd5c4c 100644
@@ -1706,7 +1706,7 @@ void ata_port_probe(struct ata_port *ap)
  *	LOCKING:
  *	None.
  */
-static void sata_print_link_status(struct ata_link *link)
+void sata_print_link_status(struct ata_link *link)
 {
 	u32 sstatus, scontrol, tmp;
 

@@ -2639,7 +2639,7 @@ int sata_link_resume(struct ata_link *li
 	return sata_link_debounce(link, params);
 }
 
-static void ata_wait_spinup(struct ata_link *link)
+void ata_wait_spinup(struct ata_link *link)
 {
 	struct ata_eh_context *ehc = &link->eh_context;
 	unsigned long end, secs;

@@ -5421,7 +5421,7 @@ void ata_dev_init(struct ata_device *dev
  *	LOCKING:
  *	Kernel thread context (may sleep)
  */
-static void ata_link_init(struct ata_port *ap, struct ata_link *link, int pmp)
+void ata_link_init(struct ata_port *ap, struct ata_link *link, int pmp)
 {
 	struct ata_device *dev;
 

@@ -5454,7 +5454,7 @@ static void ata_link_init(struct ata_por
  *	RETURNS:
  *	0 on success, -errno on failure.
  */
-static int sata_link_init_spd_limit(struct ata_link *link)
+int sata_link_init_spd_limit(struct ata_link *link)
 {
 
 	u32 scontrol, spd;

index 8ee4674..ba8b173 100644
@@ -51,10 +51,8 @@ MODULE_PARM_DESC(hotplug_polling_interva
 		 "Hotplug polling interval in milliseconds (default 2000)");
 
 static void __ata_port_freeze(struct ata_port *ap);
-static void ata_eh_finish(struct ata_port *ap);
 static void ata_eh_handle_port_suspend(struct ata_port *ap);
 static void ata_eh_handle_port_resume(struct ata_port *ap);
-static void ata_hp_poll_activate(struct ata_port *ap);
 
 
 static void ata_ering_record(struct ata_ering *ering, int is_io,

@@ -767,7 +765,7 @@ void ata_eh_qc_retry(struct ata_queued_c
  *	LOCKING:
  *	None.
  */
-static void ata_eh_detach_dev(struct ata_device *dev)
+void ata_eh_detach_dev(struct ata_device *dev)
 {
 	struct ata_link *link = dev->link;
 	struct ata_port *ap = link->ap;

@@ -804,8 +802,8 @@ static void ata_eh_detach_dev(struct ata
  *	LOCKING:
  *	None.
  */
-static void ata_eh_about_to_do(struct ata_link *link, struct ata_device *dev,
-			       unsigned int action)
+void ata_eh_about_to_do(struct ata_link *link, struct ata_device *dev,
+			unsigned int action)
 {
 	struct ata_port *ap = link->ap;
 	struct ata_eh_info *ehi = &link->eh_info;

@@ -847,8 +845,8 @@ static void ata_eh_about_to_do(struct at
  *	LOCKING:
  *	None.
  */
-static void ata_eh_done(struct ata_link *link, struct ata_device *dev,
-			unsigned int action)
+void ata_eh_done(struct ata_link *link, struct ata_device *dev,
+		 unsigned int action)
 {
 	struct ata_eh_context *ehc = &link->eh_context;
 

@@ -1441,7 +1439,7 @@ static void ata_eh_link_autopsy(struct a
  *	LOCKING:
  *	Kernel thread context (may sleep).
  */
-static void ata_eh_autopsy(struct ata_port *ap)
+void ata_eh_autopsy(struct ata_port *ap)
 {
 	struct ata_link *link;
 

@@ -1527,7 +1525,7 @@ static void ata_eh_link_report(struct at
  *	LOCKING:
  *	None.
  */
-static void ata_eh_report(struct ata_port *ap)
+void ata_eh_report(struct ata_port *ap)
 {
 	struct ata_link *link;
 

@@ -1578,9 +1576,9 @@ static int ata_eh_followup_srst_needed(i
 	return 0;
 }
 
-static int ata_eh_reset(struct ata_link *link, int classify,
-			ata_prereset_fn_t prereset, ata_reset_fn_t softreset,
-			ata_reset_fn_t hardreset, ata_postreset_fn_t postreset)
+int ata_eh_reset(struct ata_link *link, int classify,
+		 ata_prereset_fn_t prereset, ata_reset_fn_t softreset,
+		 ata_reset_fn_t hardreset, ata_postreset_fn_t postreset)
 {
 	struct ata_eh_context *ehc = &link->eh_context;
 	unsigned int *classes = ehc->classes;

@@ -2061,10 +2059,10 @@ static void ata_eh_handle_dev_fail(struc
  *	RETURNS:
  *	0 on success, -errno on failure.
  */
-static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
-			  ata_reset_fn_t softreset, ata_reset_fn_t hardreset,
-			  ata_postreset_fn_t postreset,
-			  struct ata_link **r_failed_link)
+int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
+		   ata_reset_fn_t softreset, ata_reset_fn_t hardreset,
+		   ata_postreset_fn_t postreset,
+		   struct ata_link **r_failed_link)
 {
 	struct ata_link *link;
 	struct ata_device *dev;

@@ -2218,7 +2216,7 @@ static int ata_eh_recover(struct ata_por
  *	LOCKING:
  *	None.
  */
-static void ata_eh_finish(struct ata_port *ap)
+void ata_eh_finish(struct ata_port *ap)
 {
 	int tag;
 

@@ -2428,7 +2426,7 @@ static unsigned long ata_hp_poll_delay(v
  *	LOCKING:
  *	Kernel thread context (may sleep).
  */
-static void ata_hp_poll_activate(struct ata_port *ap)
+void ata_hp_poll_activate(struct ata_port *ap)
 {
 	unsigned long flags;
 

index 92ae977..342888a 100644
@@ -54,11 +54,13 @@ extern unsigned int ata_do_simple_cmd(st
 extern int ata_dev_read_id(struct ata_device *dev, unsigned int *p_class,
 			   int post_reset, u16 *id);
 extern int ata_dev_configure(struct ata_device *dev, int print_info);
+extern void sata_print_link_status(struct ata_link *link);
 extern int sata_down_spd_limit(struct ata_link *link);
 extern int sata_set_spd_needed(struct ata_link *link);
 extern int ata_down_xfermask_limit(struct ata_device *dev, int force_pio0);
 extern int ata_set_mode(struct ata_link *link,
 			struct ata_device **r_failed_dev);
+extern void ata_wait_spinup(struct ata_link *link);
 extern void ata_qc_free(struct ata_queued_cmd *qc);
 extern void ata_qc_issue(struct ata_queued_cmd *qc);
 extern void __ata_qc_complete(struct ata_queued_cmd *qc);

@@ -68,6 +70,8 @@ extern void ata_dev_select(struct ata_po
 extern void swap_buf_le16(u16 *buf, unsigned int buf_words);
 extern int ata_flush_cache(struct ata_device *dev);
 extern void ata_dev_init(struct ata_device *dev);
+extern void ata_link_init(struct ata_port *ap, struct ata_link *link, int pmp);
+extern int sata_link_init_spd_limit(struct ata_link *link);
 extern int ata_task_ioctl(struct scsi_device *scsidev, void __user *arg);
 extern int ata_cmd_ioctl(struct scsi_device *scsidev, void __user *arg);
 extern void ata_port_init(struct ata_port *ap, struct ata_host *host,

@@ -119,7 +123,23 @@ extern enum scsi_eh_timer_return ata_scs
 extern void ata_scsi_error(struct Scsi_Host *host);
 extern void ata_port_wait_eh(struct ata_port *ap);
 extern void ata_qc_schedule_eh(struct ata_queued_cmd *qc);
+extern void ata_eh_detach_dev(struct ata_device *dev);
+extern void ata_eh_about_to_do(struct ata_link *link, struct ata_device *dev,
+			       unsigned int action);
+extern void ata_eh_done(struct ata_link *link, struct ata_device *dev,
+			unsigned int action);
+extern void ata_eh_autopsy(struct ata_port *ap);
+extern void ata_eh_report(struct ata_port *ap);
+extern int ata_eh_reset(struct ata_link *link, int classify,
+			ata_prereset_fn_t prereset, ata_reset_fn_t softreset,
+			ata_reset_fn_t hardreset, ata_postreset_fn_t postreset);
+extern int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
+			  ata_reset_fn_t softreset, ata_reset_fn_t hardreset,
+			  ata_postreset_fn_t postreset,
+			  struct ata_link **r_failed_disk);
+extern void ata_eh_finish(struct ata_port *ap);
 extern void ata_hp_poll_worker(void *data);
+extern void ata_hp_poll_activate(struct ata_port *ap);
 extern void ata_hp_poll_deactivate(struct ata_port *ap);
 
 #endif /* __LIBATA_H__ */

index 08611e2..3878dea 100644
@@ -785,8 +785,7 @@ static int ahci_softreset(struct ata_lin
 			   cmd_fis_len | AHCI_CMD_RESET | AHCI_CMD_CLR_BUSY);
 
 	tf.ctl |= ATA_SRST;
-	ata_tf_to_fis(&tf, fis, 0);
-	fis[1] &= ~(1 << 7);	/* turn off Command FIS bit */
+	ata_tf_to_fis(&tf, 0, 0, fis);
 
 	writel(1, port_mmio + PORT_CMD_ISSUE);
 

@@ -804,8 +803,7 @@ static int ahci_softreset(struct ata_lin
 	ahci_fill_cmd_slot(pp, 0, cmd_fis_len);
 
 	tf.ctl &= ~ATA_SRST;
-	ata_tf_to_fis(&tf, fis, 0);
-	fis[1] &= ~(1 << 7);	/* turn off Command FIS bit */
+	ata_tf_to_fis(&tf, 0, 0, fis);
 
 	writel(1, port_mmio + PORT_CMD_ISSUE);
 	readl(port_mmio + PORT_CMD_ISSUE);	/* flush */

@@ -857,7 +855,7 @@ static int ahci_hardreset(struct ata_lin
 	/* clear D2H reception area to properly wait for D2H FIS */
 	ata_tf_init(link->device, &tf);
 	tf.command = 0xff;
-	ata_tf_to_fis(&tf, d2h_fis, 0);
+	ata_tf_to_fis(&tf, 0, 0, d2h_fis);
 
 	rc = sata_std_hardreset(link, class);
 

@@ -976,7 +974,7 @@ static void ahci_qc_prep(struct ata_queu
 	 */
 	cmd_tbl = pp->cmd_tbl + qc->tag * AHCI_CMD_TBL_SZ;
 
-	ata_tf_to_fis(&qc->tf, cmd_tbl, 0);
+	ata_tf_to_fis(&qc->tf, 0, 1, cmd_tbl);
 	if (is_atapi) {
 		memset(cmd_tbl + AHCI_CMD_TBL_CDB, 0, 32);
 		memcpy(cmd_tbl + AHCI_CMD_TBL_CDB, qc->cdb, qc->dev->cdb_len);

index 0dd5c4c..6b3a013 100644
@@ -99,8 +99,9 @@ MODULE_VERSION(DRV_VERSION);
 /**
  *	ata_tf_to_fis - Convert ATA taskfile to SATA FIS structure
  *	@tf: Taskfile to convert
- *	@fis: Buffer into which data will output
  *	@pmp: Port multiplier port
+ *	@is_cmd: This FIS is for command
+ *	@fis: Buffer into which data will output
  *
  *	Converts a standard ATA taskfile to a Serial ATA
  *	FIS structure (Register - Host to Device).

@@ -108,12 +109,13 @@ MODULE_VERSION(DRV_VERSION);
  *	LOCKING:
  *	Inherited from caller.
  */
-
-void ata_tf_to_fis(const struct ata_taskfile *tf, u8 *fis, u8 pmp)
+void ata_tf_to_fis(const struct ata_taskfile *tf, u8 pmp, int is_cmd, u8 *fis)
 {
-	fis[0] = 0x27;	/* Register - Host to Device FIS */
-	fis[1] = (pmp & 0xf) | (1 << 7); /* Port multiplier number,
-					    bit 7 indicates Command FIS */
+	fis[0] = 0x27;			/* Register - Host to Device FIS */
+	fis[1] = pmp & 0xf;		/* Port multiplier number*/
+	if (is_cmd)
+		fis[1] |= (1 << 7);	/* bit 7 indicates Command FIS */
+
 	fis[2] = tf->command;
 	fis[3] = tf->feature;
 

index bf1f3e2..da69273 100644
@@ -335,7 +335,7 @@ static void qs_qc_prep(struct ata_queued
 	buf[28] = dflags;
 
 	/* frame information structure (FIS) */
-	ata_tf_to_fis(&qc->tf, &buf[32], 0);
+	ata_tf_to_fis(&qc->tf, 0, 1, &buf[32]);
 }
 
 static inline void qs_packet_start(struct ata_queued_cmd *qc)

index 8d6651f..1030496 100644
@@ -711,7 +711,7 @@ static void sil24_qc_prep(struct ata_que
 	}
 
 	prb->ctrl = cpu_to_le16(ctrl);
-	ata_tf_to_fis(&qc->tf, prb->fis, 0);
+	ata_tf_to_fis(&qc->tf, qc->dev->link->pmp, 1, prb->fis);
 
 	if (qc->flags & ATA_QCFLAG_DMAMAP)
 		sil24_fill_sg(qc, sge);

index 676e1d9..1b91a7c 100644
@@ -787,7 +787,8 @@ extern u32 ata_wait_register(void __iome
  */
 extern void ata_tf_load(struct ata_port *ap, const struct ata_taskfile *tf);
 extern void ata_tf_read(struct ata_port *ap, struct ata_taskfile *tf);
-extern void ata_tf_to_fis(const struct ata_taskfile *tf, u8 *fis, u8 pmp);
+extern void ata_tf_to_fis(const struct ata_taskfile *tf,
+			  u8 pmp, int is_cmd, u8 *fis);
 extern void ata_tf_from_fis(const u8 *fis, struct ata_taskfile *tf);
 extern void ata_noop_dev_select (struct ata_port *ap, unsigned int device);
 extern void ata_std_dev_select (struct ata_port *ap, unsigned int device);

index 3878dea..d2d43cf 100644
@@ -251,6 +251,7 @@ static const struct ata_port_operations 
 
 	.tf_read		= ahci_tf_read,
 
+	.qc_defer		= ata_std_qc_defer,
 	.qc_prep		= ahci_qc_prep,
 	.qc_issue		= ahci_qc_issue,
 

@@ -284,6 +285,7 @@ static const struct ata_port_operations 
 
 	.tf_read		= ahci_tf_read,
 
+	.qc_defer		= ata_std_qc_defer,
 	.qc_prep		= ahci_qc_prep,
 	.qc_issue		= ahci_qc_issue,
 

index 6b3a013..5f0835d 100644
@@ -3485,6 +3485,37 @@ int ata_check_atapi_dma(struct ata_queue
 
 	return rc;
 }
+
+/**
+ *	ata_std_qc_defer - Check whether a qc needs to be deferred
+ *	@qc: ATA command in question
+ *
+ *	Non-NCQ commands cannot run with any other command, NCQ or
+ *	not.  As upper layer only knows the queue depth, we are
+ *	responsible for maintaining exclusion.  This function checks
+ *	whether a new command @qc can be issued.
+ *
+ *	LOCKING:
+ *	spin_lock_irqsave(host lock)
+ *
+ *	RETURNS:
+ *	ATA_DEFER_* if deferring is needed, 0 otherwise.
+ */
+int ata_std_qc_defer(struct ata_queued_cmd *qc)
+{
+	struct ata_link *link = qc->dev->link;
+
+	if (qc->tf.protocol == ATA_PROT_NCQ) {
+		if (!ata_tag_valid(link->active_tag))
+			return 0;
+	} else {
+		if (!ata_tag_valid(link->active_tag) && !link->sactive)
+			return 0;
+	}
+
+	return ATA_DEFER_LINK;
+}
+
 /**
  *	ata_qc_prep - Prepare taskfile for submission
  *	@qc: Metadata associated with taskfile to be prepared

@@ -5599,6 +5630,13 @@ static struct ata_port * ata_port_add(co
 
 	shost->transportt = &ata_scsi_transport_template;
 
+	/* Schedule policy is determined by ->qc_defer() callback and
+	 * it needs to see every deferred qc.  Set host_blocked to 1
+	 * to prevent SCSI midlayer from automatically deferring
+	 * requests.
+	 */
+	shost->max_host_blocked = 1;
+
 	ap = ata_shost_to_port(shost);
 
 	ata_port_init(ap, host, ent, port_no);

@@ -6299,6 +6337,7 @@ EXPORT_SYMBOL_GPL(ata_interrupt);
 EXPORT_SYMBOL_GPL(ata_mmio_data_xfer);
 EXPORT_SYMBOL_GPL(ata_pio_data_xfer);
 EXPORT_SYMBOL_GPL(ata_pio_data_xfer_noirq);
+EXPORT_SYMBOL_GPL(ata_std_qc_defer);
 EXPORT_SYMBOL_GPL(ata_qc_prep);
 EXPORT_SYMBOL_GPL(ata_noop_qc_prep);
 EXPORT_SYMBOL_GPL(ata_bmdma_setup);

93 lines not on this page · raw message

index 1030496..9564e49 100644
@@ -396,6 +396,7 @@ static const struct ata_port_operations 
 
 	.tf_read		= sil24_tf_read,
 
+	.qc_defer		= ata_std_qc_defer,
 	.qc_prep		= sil24_qc_prep,
 	.qc_issue		= sil24_qc_issue,
 

index 1b91a7c..12e866d 100644
@@ -263,6 +263,10 @@ enum {
 	/* ering size */
 	ATA_ERING_SIZE		= 32,
 
+	/* return values for ->qc_defer */
+	ATA_DEFER_LINK		= 1,
+	ATA_DEFER_PORT		= 2,
+
 	/* desc_len for ata_eh_info and context */
 	ATA_EH_DESC_LEN		= 80,
 

@@ -633,6 +637,7 @@ struct ata_port_operations {
 
 	void (*data_xfer) (struct ata_device *, unsigned char *, unsigned int, int);
 
+	int (*qc_defer) (struct ata_queued_cmd *qc);
 	void (*qc_prep) (struct ata_queued_cmd *qc);
 	unsigned int (*qc_issue) (struct ata_queued_cmd *qc);
 

@@ -805,6 +810,7 @@ extern void ata_pio_data_xfer(struct ata
 			      unsigned int buflen, int write_data);
 extern void ata_pio_data_xfer_noirq(struct ata_device *adev, unsigned char *buf,
 			      unsigned int buflen, int write_data);
+extern int ata_std_qc_defer(struct ata_queued_cmd *qc);
 extern void ata_qc_prep(struct ata_queued_cmd *qc);
 extern void ata_noop_qc_prep(struct ata_queued_cmd *qc);
 extern unsigned int ata_qc_issue_prot(struct ata_queued_cmd *qc);

index 5f0835d..58836e3 100644
@@ -1031,6 +1031,7 @@ unsigned ata_exec_internal(struct ata_de
 	struct ata_queued_cmd *qc;
 	unsigned int tag, preempted_tag;
 	u32 preempted_sactive, preempted_qc_active;
+	int preempted_nr_active_links;
 	DECLARE_COMPLETION_ONSTACK(wait);
 	unsigned long flags;
 	unsigned int err_mask;

@@ -1069,9 +1070,11 @@ unsigned ata_exec_internal(struct ata_de
 	preempted_tag = link->active_tag;
 	preempted_sactive = link->sactive;
 	preempted_qc_active = ap->qc_active;
+	preempted_nr_active_links = ap->nr_active_links;
 	link->active_tag = ATA_TAG_POISON;
 	link->sactive = 0;
 	ap->qc_active = 0;
+	ap->nr_active_links = 0;
 
 	/* prepare & issue qc */
 	qc->tf = *tf;

@@ -1141,6 +1144,7 @@ unsigned ata_exec_internal(struct ata_de
 	link->active_tag = preempted_tag;
 	link->sactive = preempted_sactive;
 	ap->qc_active = preempted_qc_active;
+	ap->nr_active_links = preempted_nr_active_links;
 
 	/* XXX - Some LLDDs (sata_mv) disable port on command failure.
 	 * Until those drivers are fixed, we detect the condition

@@ -4580,10 +4584,18 @@ void __ata_qc_complete(struct ata_queued
 		ata_sg_clean(qc);
 
 	/* command should be marked inactive atomically with qc completion */
-	if (qc->tf.protocol == ATA_PROT_NCQ)
+	if (qc->tf.protocol == ATA_PROT_NCQ) {
 		link->sactive &= ~(1 << qc->tag);
-	else
+		if (!link->sactive)
+			ap->nr_active_links--;
+	} else {
 		link->active_tag = ATA_TAG_POISON;
+		ap->nr_active_links--;
+	}
+
+	/* clear exclusive status */
+	if (unlikely(qc->flags & ATA_QCFLAG_CLEAR_EXCL))
+		ap->excl_link = NULL;
 
 	/* atapi: mark qc as inactive to prevent the interrupt handler
 	 * from completing the command twice later, before the error handler

@@ -4754,9 +4766,14 @@ void ata_qc_issue(struct ata_queued_cmd 
 
 	if (qc->tf.protocol == ATA_PROT_NCQ) {
 		WARN_ON(link->sactive & (1 << qc->tag));
+
+		if (!link->sactive)
+			ap->nr_active_links++;
 		link->sactive |= 1 << qc->tag;
 	} else {
 		WARN_ON(link->sactive);
+
+		ap->nr_active_links++;
 		link->active_tag = qc->tag;
 	}
 

index ba8b173..103fc5e 100644
@@ -286,6 +286,7 @@ void ata_scsi_error(struct Scsi_Host *ho
 
 		ap->pflags |= ATA_PFLAG_EH_IN_PROGRESS;
 		ap->pflags &= ~ATA_PFLAG_EH_PENDING;
+		ap->excl_link = NULL;	/* don't maintain exclusion over EH */
 
 		spin_unlock_irqrestore(ap->lock, flags);
 

@@ -2246,6 +2247,10 @@ void ata_eh_finish(struct ata_port *ap)
 			}
 		}
 	}
+
+	/* make sure nr_active_links is zero after EH */
+	WARN_ON(ap->nr_active_links);
+	ap->nr_active_links = 0;
 }
 
 /**

index 12e866d..0191ac8 100644
@@ -206,6 +206,7 @@ enum {
 	ATA_QCFLAG_DMAMAP	= ATA_QCFLAG_SG | ATA_QCFLAG_SINGLE,
 	ATA_QCFLAG_IO		= (1 << 3), /* standard IO command */
 	ATA_QCFLAG_RESULT_TF	= (1 << 4), /* result TF requested */
+	ATA_QCFLAG_CLEAR_EXCL	= (1 << 5), /* clear excl_link on completion */
 
 	ATA_QCFLAG_FAILED	= (1 << 16), /* cmd failed and is owned by EH */
 	ATA_QCFLAG_SENSE_VALID	= (1 << 17), /* sense data valid */

@@ -579,11 +580,13 @@ struct ata_port {
 	struct ata_queued_cmd	qcmd[ATA_MAX_QUEUE];
 	unsigned long		qc_allocated;
 	unsigned int		qc_active;
+	int			nr_active_links; /* #links with active qcs */
 
 	struct ata_link		link;	/* host default link */
 
 	int			nr_pmp_links;	/* nr of available PMP links */
 	struct ata_link		*pmp_link;	/* array of PMP links */
+	struct ata_link		*excl_link;	/* for PMP qc exclusion */
 
 	struct ata_port_stats	stats;
 	struct ata_host		*host;

@@ -1068,6 +1071,11 @@ static inline int ata_link_max_devices(c
 	return 1;
 }
 
+static inline int ata_link_active(struct ata_link *link)
+{
+	return ata_tag_valid(link->active_tag) || link->sactive;
+}
+
 static inline struct ata_link *ata_port_first_link(struct ata_port *ap)
 {
 	if (ap->nr_pmp_links)