3 files changed, 32 insertions, 0 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index d3e78d97529d..5532a6564d05 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -7303,6 +7303,7 @@ EXPORT_SYMBOL_GPL(ata_pci_default_filter);
 EXPORT_SYMBOL_GPL(ata_pci_clear_simplex);
 #endif /* CONFIG_PCI */
 
+EXPORT_SYMBOL_GPL(sata_pmp_qc_defer_cmd_switch);
 EXPORT_SYMBOL_GPL(sata_pmp_read_init_tf);
 EXPORT_SYMBOL_GPL(sata_pmp_read_val);
 EXPORT_SYMBOL_GPL(sata_pmp_write_init_tf);
diff --git a/drivers/ata/libata-pmp.c b/drivers/ata/libata-pmp.c
index eeffce636d0c..f6c4b11336e9 100644
--- a/drivers/ata/libata-pmp.c
+++ b/drivers/ata/libata-pmp.c
@@ -70,6 +70,36 @@ static int sata_pmp_write(struct ata_link *link, int reg, u32 val)
 }
 
 /**
+ *      sata_pmp_qc_defer_cmd_switch - qc_defer for command switching PMP
+ *      @qc: ATA command in question
+ *
+ *      A host which has command switching PMP support cannot issue
+ *      commands to multiple links simultaneously.
+ *
+ *      LOCKING:
+ *      spin_lock_irqsave(host lock)
+ *
+ *      RETURNS:
+ *      ATA_DEFER_* if deferring is needed, 0 otherwise.
+ */
+int sata_pmp_qc_defer_cmd_switch(struct ata_queued_cmd *qc)
+{
+        struct ata_link *link = qc->dev->link;
+        struct ata_port *ap = link->ap;
+
+        if (ap->excl_link == NULL || ap->excl_link == link) {
+                if (ap->nr_active_links == 0 || ata_link_active(link)) {
+                        qc->flags |= ATA_QCFLAG_CLEAR_EXCL;
+                        return ata_std_qc_defer(qc);
+                }
+
+                ap->excl_link = link;
+        }
+
+        return ATA_DEFER_PORT;
+}
+
+/**
  *      sata_pmp_read_init_tf - initialize TF for PMP read
  *      @tf: taskfile to initialize
  *      @dev: PMP dev
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 3cfdb5f67621..ca296a575c4a 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -947,6 +947,7 @@ extern unsigned long ata_pci_default_filter(struct ata_device *, unsigned long);
 /*
  * PMP
  */
+extern int sata_pmp_qc_defer_cmd_switch(struct ata_queued_cmd *qc);
 extern void sata_pmp_read_init_tf(struct ata_taskfile *tf,
                                   struct ata_device *dev, int pmp, int reg);
 extern u32 sata_pmp_read_val(const struct ata_taskfile *tf);