[PATCH v9 6/9] scsi: ibmvfc: extend channel reg/dereg helpers for async sub-CRQ

[Tyrel Datwyler <tyreld@linux.ibm.com>]

From: Dave Marquardt <davemarq@linux.ibm.com>

ibmvfc_register_channel() and ibmvfc_deregister_channel() previously only
handled indexed sub-CRQ channels drawn from the channels->scrqs[] array.
The async sub-CRQ (vhost->async_sub_crq) had no registration path through
these helpers, requiring separate handling.

Extend both functions to accept a negative index as a sentinel value
signalling that the async sub-CRQ should be operated on instead of an
indexed scrq entry. When index < 0, the queue pointer is set to
&vhost->async_sub_crq, the IRQ is named "ibmvfc-<addr>-async", and the
handler is set to ibmvfc_interrupt_async_subq rather than the per-protocol
ibmvfc_interrupt_mq handler. hwq_id assignment is skipped for the async
queue since it has no meaningful hardware queue index.

Stopped marking ibmvfc_interrupt_async_subq as __maybe_unused.

Error messages in both paths are updated to distinguish async sub-CRQ
failures from indexed sub-CRQ failures. Kernel-doc headers are added to
both functions documenting the negative-index convention.

Signed-off-by: Dave Marquardt <davemarq@linux.ibm.com>
Acked-by: Tyrel Datwyler <tyreld@linux.ibm.com>
---
 drivers/scsi/ibmvscsi/ibmvfc-core.c | 93 ++++++++++++++++++++++-------
 1 file changed, 70 insertions(+), 23 deletions(-)

diff --git a/drivers/scsi/ibmvscsi/ibmvfc-core.c b/drivers/scsi/ibmvscsi/ibmvfc-core.c
index 553fca31cb3a..fa312a58471f 100644
--- a/drivers/scsi/ibmvscsi/ibmvfc-core.c
+++ b/drivers/scsi/ibmvscsi/ibmvfc-core.c
@@ -4420,7 +4420,7 @@ static void ibmvfc_drain_async_subq(struct ibmvfc_queue *scrq)
  * @scrq_instance: async subq
  *
  **/
-static irqreturn_t __maybe_unused ibmvfc_interrupt_async_subq(int irq, void *scrq_instance)
+static irqreturn_t ibmvfc_interrupt_async_subq(int irq, void *scrq_instance)
 {
 	struct ibmvfc_queue *scrq = (struct ibmvfc_queue *)scrq_instance;
 
@@ -6811,13 +6811,29 @@ static int ibmvfc_init_crq(struct ibmvfc_host *vhost)
 	return retrc;
 }
 
+/**
+ * ibmvfc_register_channel - Register a sub-CRQ channel with the hypervisor
+ * @vhost:	ibmvfc host struct
+ * @channels:	ibmvfc channels struct containing the channel array and protocol
+ * @index:	index into the channels array for the queue to register, or
+ *		a negative value to register the async sub-CRQ
+ *
+ * Register a sub-CRQ with the hypervisor via h_reg_sub_crq, map its hardware
+ * IRQ to a Linux IRQ, and bind an interrupt handler to it. The handler is
+ * selected based on the channel protocol (SCSI or NVMe) for normal queues, or
+ * set to the async sub-CRQ handler when @index is negative.
+ *
+ * Return value:
+ *	0 on success / non-zero on failure
+ **/
 static int ibmvfc_register_channel(struct ibmvfc_host *vhost,
 				   struct ibmvfc_channels *channels,
 				   int index)
 {
 	struct device *dev = vhost->dev;
 	struct vio_dev *vdev = to_vio_dev(dev);
-	struct ibmvfc_queue *scrq = &channels->scrqs[index];
+	bool is_async = index < 0;
+	struct ibmvfc_queue *scrq = !is_async ? &channels->scrqs[index] : &vhost->async_sub_crq;
 	int rc = -ENOMEM;
 
 	ENTER;
@@ -6837,36 +6853,49 @@ static int ibmvfc_register_channel(struct ibmvfc_host *vhost,
 
 	if (!scrq->irq) {
 		rc = -EINVAL;
-		dev_err(dev, "Error mapping sub-crq[%d] irq\n", index);
+		if (!is_async)
+			dev_err(dev, "Error mapping sub-crq[%d] irq\n", index);
+		else
+			dev_err(dev, "Error mapping async sub-crq irq\n");
 		goto irq_failed;
 	}
 
-	switch (channels->protocol) {
-	case IBMVFC_PROTO_SCSI:
-		snprintf(scrq->name, sizeof(scrq->name), "ibmvfc-%x-scsi%d",
-			 vdev->unit_address, index);
-		scrq->handler = ibmvfc_interrupt_mq;
-		break;
-	case IBMVFC_PROTO_NVME:
-		snprintf(scrq->name, sizeof(scrq->name), "ibmvfc-%x-nvmf%d",
-			 vdev->unit_address, index);
-		scrq->handler = ibmvfc_interrupt_mq;
-		break;
-	default:
-		dev_err(dev, "Unknown channel protocol (%d)\n",
-			channels->protocol);
-		goto irq_failed;
+	if (!is_async) {
+		switch (channels->protocol) {
+		case IBMVFC_PROTO_SCSI:
+			snprintf(scrq->name, sizeof(scrq->name), "ibmvfc-%x-scsi%d",
+				 vdev->unit_address, index);
+			scrq->handler = ibmvfc_interrupt_mq;
+			break;
+		case IBMVFC_PROTO_NVME:
+			snprintf(scrq->name, sizeof(scrq->name), "ibmvfc-%x-nvmf%d",
+				 vdev->unit_address, index);
+			scrq->handler = ibmvfc_interrupt_mq;
+			break;
+		default:
+			dev_err(dev, "Unknown channel protocol (%d)\n",
+				channels->protocol);
+			goto irq_failed;
+		}
+	} else {
+		snprintf(scrq->name, sizeof(scrq->name), "ibmvfc-%x-async",
+			 vdev->unit_address);
+		scrq->handler = ibmvfc_interrupt_async_subq;
 	}
 
 	rc = request_irq(scrq->irq, scrq->handler, 0, scrq->name, scrq);
 
 	if (rc) {
-		dev_err(dev, "Couldn't register sub-crq[%d] irq\n", index);
+		if (!is_async)
+			dev_err(dev, "Couldn't register sub-crq[%d] irq\n", index);
+		else
+			dev_err(dev, "Couldn't register async sub-crq irq\n");
 		irq_dispose_mapping(scrq->irq);
 		goto irq_failed;
 	}
 
-	scrq->hwq_id = index;
+	if (!is_async)
+		scrq->hwq_id = index;
 
 	LEAVE;
 	return 0;
@@ -6880,13 +6909,26 @@ static int ibmvfc_register_channel(struct ibmvfc_host *vhost,
 	return rc;
 }
 
+/**
+ * ibmvfc_deregister_channel - Deregister a sub-CRQ channel with the hypervisor
+ * @vhost:	ibmvfc host struct
+ * @channels:	ibmvfc channels struct containing the sub-CRQ array
+ * @index:	index into the sub-CRQ array, or -1 to deregister the
+ *		asynchronous sub-CRQ
+ *
+ * Frees the IRQ, disposes of the IRQ mapping, and calls H_FREE_SUB_CRQ to
+ * release the sub-CRQ with the hypervisor. On success the queue message
+ * buffer is zeroed and the current index is reset. If H_FREE_SUB_CRQ fails,
+ * an error is logged but the channel resources are cleaned up regardless.
+ */
 static void ibmvfc_deregister_channel(struct ibmvfc_host *vhost,
 				      struct ibmvfc_channels *channels,
 				      int index)
 {
 	struct device *dev = vhost->dev;
 	struct vio_dev *vdev = to_vio_dev(dev);
-	struct ibmvfc_queue *scrq = &channels->scrqs[index];
+	bool is_async = index < 0;
+	struct ibmvfc_queue *scrq = !is_async ? &channels->scrqs[index] : &vhost->async_sub_crq;
 	long rc;
 
 	ENTER;
@@ -6900,8 +6942,13 @@ static void ibmvfc_deregister_channel(struct ibmvfc_host *vhost,
 					scrq->cookie);
 	} while (rc == H_BUSY || H_IS_LONG_BUSY(rc));
 
-	if (rc)
-		dev_err(dev, "Failed to free sub-crq[%d]: rc=%ld\n", index, rc);
+	if (rc) {
+		if (!is_async)
+			dev_err(dev, "Failed to free sub-crq[%d]: rc=%ld\n",
+				index, rc);
+		else
+			dev_err(dev, "Failed to free async sub-crq: rc=%ld\n", rc);
+	}
 
 	/* Clean out the queue */
 	memset(scrq->msgs.crq, 0, PAGE_SIZE);
-- 
2.55.0