[PATCH v13 08/11] scsi: ibmvfc: add interrupt routine for asynchronous sub CRQ

[Dave Marquardt via B4 Relay <devnull+davemarq.linux.ibm.com@kernel.org>]

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

Add ibmvfc_interrupt_async_subq(), an IRQ handler dedicated to
asynchronous sub-CRQ events from the adapter. The handler disables
the sub-CRQ IRQ and then calls ibmvfc_drain_async_subq() to consume
all pending entries before re-enabling interrupts.

Add ibmvfc_next_async_scrq() to traverse the async sub-CRQ ring
directly via msgs.async_scrq[], returning a typed
struct ibmvfc_async_sub_crq * without the cast that would be needed
when going through ibmvfc_next_scrq().

ibmvfc_drain_async_subq() holds the host lock and per-queue q_lock
while processing. It loops over available entries via
ibmvfc_next_async_scrq(), wrapping each in a struct
ibmvfc_async_crq_event and dispatching to ibmvfc_handle_async(),
then clears the valid bit and issues a write barrier. After draining,
it re-enables the sub-CRQ IRQ and performs one final check for a
newly arrived entry to close the IRQ-enable race; if one is found it
is processed before exiting the loop.

Signed-off-by: Dave Marquardt <davemarq@linux.ibm.com>
Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
---
 drivers/scsi/ibmvscsi/ibmvfc-core.c | 66 +++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/drivers/scsi/ibmvscsi/ibmvfc-core.c b/drivers/scsi/ibmvscsi/ibmvfc-core.c
index 6db9df91e9e6..32bc00a4be7e 100644
--- a/drivers/scsi/ibmvscsi/ibmvfc-core.c
+++ b/drivers/scsi/ibmvscsi/ibmvfc-core.c
@@ -4374,6 +4374,72 @@ static struct ibmvfc_crq *ibmvfc_next_scrq(struct ibmvfc_queue *scrq)
 	return crq;
 }
 
+static struct ibmvfc_async_sub_crq *ibmvfc_next_async_scrq(struct ibmvfc_queue *scrq)
+{
+	struct ibmvfc_async_sub_crq *crq;
+
+	crq = &scrq->msgs.async_scrq[scrq->cur];
+	if (crq->valid & 0x80) {
+		if (++scrq->cur == scrq->size)
+			scrq->cur = 0;
+		rmb();
+	} else
+		crq = NULL;
+
+	return crq;
+}
+
+static void ibmvfc_drain_async_subq(struct ibmvfc_queue *scrq)
+{
+	struct ibmvfc_host *vhost = scrq->vhost;
+	struct ibmvfc_async_crq_event ae = {
+		.type = IBMVFC_ASYNC_CRQ_SUB,
+	};
+	struct ibmvfc_async_sub_crq *crq;
+	unsigned long flags;
+	int done = 0;
+
+	spin_lock_irqsave(&vhost->host->host_lock, flags);
+	spin_lock(scrq->q_lock);
+	while (!done) {
+		while ((crq = ibmvfc_next_async_scrq(scrq)) != NULL) {
+			ae.subq = *crq;
+			ibmvfc_handle_async(&ae, scrq->vhost);
+			crq->valid = 0;
+			wmb();	/* complete write */
+		}
+
+		ibmvfc_toggle_scrq_irq(scrq, 1);
+		crq = ibmvfc_next_async_scrq(scrq);
+		if (crq != NULL) {
+			ae.subq = *crq;
+			ibmvfc_toggle_scrq_irq(scrq, 0);
+			ibmvfc_handle_async(&ae, scrq->vhost);
+			crq->valid = 0;
+			wmb();	/* complete write */
+		} else
+			done = 1;
+	}
+	spin_unlock(scrq->q_lock);
+	spin_unlock_irqrestore(&vhost->host->host_lock, flags);
+}
+
+/**
+ * ibmvfc_interrupt_async_subq - Handle an async event from the adapter
+ * @irq:           interrupt request
+ * @scrq_instance: async subq
+ *
+ **/
+static irqreturn_t __maybe_unused ibmvfc_interrupt_async_subq(int irq, void *scrq_instance)
+{
+	struct ibmvfc_queue *scrq = (struct ibmvfc_queue *)scrq_instance;
+
+	ibmvfc_toggle_scrq_irq(scrq, 0);
+	ibmvfc_drain_async_subq(scrq);
+
+	return IRQ_HANDLED;
+}
+
 static void ibmvfc_drain_sub_crq(struct ibmvfc_queue *scrq)
 {
 	struct ibmvfc_crq *crq;

-- 
2.55.0