[git:media_stage/master] media: cec-pin: fix interrupt en/disable handling

[Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>]

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Subject: media: cec-pin: fix interrupt en/disable handling
Author:  Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
Date:    Wed Dec 1 13:41:25 2021 +0100

The en/disable_irq() functions keep track of the 'depth': i.e. if
interrupts are disabled twice, then it needs to enable_irq() calls to
enable them again. The cec-pin framework didn't take this into accound
and could disable irqs multiple times, and it expected that a single
enable_irq() would enable them again.

Move all calls to en/disable_irq() to the kthread where it is easy
to keep track of the current irq state and ensure that multiple
en/disable_irq calls never happen.

If interrupts where disabled twice, then they would never turn on
again, leaving the CEC adapter in a dead state.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
Fixes: 865463fc03ed (media: cec-pin: add error injection support)
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>

 drivers/media/cec/core/cec-pin.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

---

diff --git a/drivers/media/cec/core/cec-pin.c b/drivers/media/cec/core/cec-pin.c
index 2b6459df1e94..21f0f749713e 100644
--- a/drivers/media/cec/core/cec-pin.c
+++ b/drivers/media/cec/core/cec-pin.c
@@ -1033,6 +1033,7 @@ static int cec_pin_thread_func(void *_adap)
 {
 	struct cec_adapter *adap = _adap;
 	struct cec_pin *pin = adap->pin;
+	bool irq_enabled = false;
 
 	for (;;) {
 		wait_event_interruptible(pin->kthread_waitq,
@@ -1060,6 +1061,7 @@ static int cec_pin_thread_func(void *_adap)
 				ns_to_ktime(pin->work_rx_msg.rx_ts));
 			msg->len = 0;
 		}
+
 		if (pin->work_tx_status) {
 			unsigned int tx_status = pin->work_tx_status;
 
@@ -1083,27 +1085,39 @@ static int cec_pin_thread_func(void *_adap)
 		switch (atomic_xchg(&pin->work_irq_change,
 				    CEC_PIN_IRQ_UNCHANGED)) {
 		case CEC_PIN_IRQ_DISABLE:
-			pin->ops->disable_irq(adap);
+			if (irq_enabled) {
+				pin->ops->disable_irq(adap);
+				irq_enabled = false;
+			}
 			cec_pin_high(pin);
 			cec_pin_to_idle(pin);
 			hrtimer_start(&pin->timer, ns_to_ktime(0),
 				      HRTIMER_MODE_REL);
 			break;
 		case CEC_PIN_IRQ_ENABLE:
+			if (irq_enabled)
+				break;
 			pin->enable_irq_failed = !pin->ops->enable_irq(adap);
 			if (pin->enable_irq_failed) {
 				cec_pin_to_idle(pin);
 				hrtimer_start(&pin->timer, ns_to_ktime(0),
 					      HRTIMER_MODE_REL);
+			} else {
+				irq_enabled = true;
 			}
 			break;
 		default:
 			break;
 		}
-
 		if (kthread_should_stop())
 			break;
 	}
+	if (pin->ops->disable_irq && irq_enabled)
+		pin->ops->disable_irq(adap);
+	hrtimer_cancel(&pin->timer);
+	cec_pin_read(pin);
+	cec_pin_to_idle(pin);
+	pin->state = CEC_ST_OFF;
 	return 0;
 }
 
@@ -1129,13 +1143,7 @@ static int cec_pin_adap_enable(struct cec_adapter *adap, bool enable)
 		hrtimer_start(&pin->timer, ns_to_ktime(0),
 			      HRTIMER_MODE_REL);
 	} else {
-		if (pin->ops->disable_irq)
-			pin->ops->disable_irq(adap);
-		hrtimer_cancel(&pin->timer);
 		kthread_stop(pin->kthread);
-		cec_pin_read(pin);
-		cec_pin_to_idle(pin);
-		pin->state = CEC_ST_OFF;
 	}
 	return 0;
 }
@@ -1156,11 +1164,8 @@ void cec_pin_start_timer(struct cec_pin *pin)
 	if (pin->state != CEC_ST_RX_IRQ)
 		return;
 
-	atomic_set(&pin->work_irq_change, CEC_PIN_IRQ_UNCHANGED);
-	pin->ops->disable_irq(pin->adap);
-	cec_pin_high(pin);
-	cec_pin_to_idle(pin);
-	hrtimer_start(&pin->timer, ns_to_ktime(0), HRTIMER_MODE_REL);
+	atomic_set(&pin->work_irq_change, CEC_PIN_IRQ_DISABLE);
+	wake_up_interruptible(&pin->kthread_waitq);
 }
 
 static int cec_pin_adap_transmit(struct cec_adapter *adap, u8 attempts,