[PATCH v2 3/4] genirq: Add support for IRQF_COND_ONESHOT

[Jan Kiszka <jan.kiszka@xxxxxx>]

From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>

Provide an adaptive version of IRQF_ONESHOT: If the line is exclusively used,
IRQF_COND_ONESHOT provides the same semantics as IRQF_ONESHOT. If it is
shared, the line will be unmasked directly after the hardirq handler, just as
if IRQF_COND_ONESHOT was not provided.

Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
 include/linux/interrupt.h |    3 +++
 kernel/irq/manage.c       |   19 ++++++++++++++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index c6323a2..f462807 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -56,6 +56,8 @@
  *                irq line disabled until the threaded handler has been run.
  * IRQF_NO_SUSPEND - Do not disable this IRQ during suspend
  * IRQF_ADAPTIVE - Request notification about upcoming interrupt line sharing
+ * IRQF_COND_ONESHOT - If line is not shared, keep interrupt disabled after
+ *                     hardirq handler finshed.
  *
  */
 #define IRQF_DISABLED		0x00000020
@@ -69,6 +71,7 @@
 #define IRQF_ONESHOT		0x00002000
 #define IRQF_NO_SUSPEND		0x00004000
 #define IRQF_ADAPTIVE		0x00008000
+#define IRQF_COND_ONESHOT	0x00010000
 
 #define IRQF_TIMER		(__IRQF_TIMER | IRQF_NO_SUSPEND)
 
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index a4557eb..948b7c9 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -580,7 +580,7 @@ static int irq_thread(void *data)
 	struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO/2, };
 	struct irqaction *action = data;
 	struct irq_desc *desc = irq_to_desc(action->irq);
-	int wake, oneshot = desc->status & IRQ_ONESHOT;
+	int wake, oneshot;
 
 	sched_setscheduler(current, SCHED_FIFO, &param);
 	current->irqaction = action;
@@ -603,6 +603,7 @@ static int irq_thread(void *data)
 			desc->status |= IRQ_PENDING;
 			raw_spin_unlock_irq(&desc->lock);
 		} else {
+			oneshot = desc->status & IRQ_ONESHOT;
 			raw_spin_unlock_irq(&desc->lock);
 
 			action->thread_fn(action->irq, action->dev_id);
@@ -756,6 +757,15 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		shared = 1;
 
 		desc->irq_data.status |= IRQS_SHARED;
+		desc->status &= ~IRQ_ONESHOT;
+
+		/* Unmask if the interrupt was masked due to oneshot mode. */
+		if ((desc->status &
+		     (IRQ_INPROGRESS | IRQ_DISABLED | IRQ_MASKED)) ==
+		    IRQ_MASKED) {
+			desc->irq_data.chip->irq_unmask(&desc->irq_data);
+			desc->status &= ~IRQ_MASKED;
+		}
 	}
 
 	if (!shared) {
@@ -780,7 +790,7 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING | IRQ_ONESHOT |
 				  IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);
 
-		if (new->flags & IRQF_ONESHOT)
+		if (new->flags & (IRQF_ONESHOT | IRQF_COND_ONESHOT))
 			desc->status |= IRQ_ONESHOT;
 
 		if (!(desc->status & IRQ_NOAUTOEN)) {
@@ -931,8 +941,11 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 			desc->irq_data.chip->irq_shutdown(&desc->irq_data);
 		else
 			desc->irq_data.chip->irq_disable(&desc->irq_data);
-	} else if (!desc->action->next)
+	} else if (!desc->action->next) {
 		single_handler = true;
+		if (desc->action->flags & IRQF_COND_ONESHOT)
+			desc->status |= IRQ_ONESHOT;
+	}
 
 #ifdef CONFIG_SMP
 	/* make sure affinity_hint is cleaned up */
-- 
1.7.1

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