can: m_can: Do not cancel timer from within timer

On setups without interrupts, the interrupt handler is called from a
timer callback. For non-peripheral receives napi is scheduled,
interrupts are disabled and the timer is canceled with a blocking call.
In case of an error this can happen as well.

Check if napi is scheduled in the timer callback after the interrupt
handler executed. If napi is scheduled, the timer is disabled. It will
be reenabled by m_can_poll().

Return error values from the interrupt handler so that interrupt threads
and timer callback can deal differently with it. In case of the timer
we only disable the timer. The rest will be done when stopping the
interface.

Fixes: b382380c ("can: m_can: Add hrtimer to generate software interrupt")
Fixes: a163c576 ("can: m_can: Start/Cancel polling timer together with interrupts")
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20240805183047.305630-5-msp@baylibre.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -487,7 +487,7 @@ static inline void m_can_disable_all_interrupts(struct m_can_classdev *cdev)
 
 	if (!cdev->net->irq) {
 		dev_dbg(cdev->dev, "Stop hrtimer\n");
-		hrtimer_cancel(&cdev->hrtimer);
+		hrtimer_try_to_cancel(&cdev->hrtimer);
 	}
 }
 
@@ -1201,11 +1201,15 @@ static void m_can_coalescing_update(struct m_can_classdev *cdev, u32 ir)
 			      HRTIMER_MODE_REL);
 }
 
-static irqreturn_t m_can_isr(int irq, void *dev_id)
+/* This interrupt handler is called either from the interrupt thread or a
+ * hrtimer. This has implications like cancelling a timer won't be possible
+ * blocking.
+ */
+static int m_can_interrupt_handler(struct m_can_classdev *cdev)
 {
-	struct net_device *dev = (struct net_device *)dev_id;
-	struct m_can_classdev *cdev = netdev_priv(dev);
+	struct net_device *dev = cdev->net;
 	u32 ir;
+	int ret;
 
 	if (pm_runtime_suspended(cdev->dev))
 		return IRQ_NONE;
@@ -1232,11 +1236,9 @@ static irqreturn_t m_can_isr(int irq, void *dev_id)
 			m_can_disable_all_interrupts(cdev);
 			napi_schedule(&cdev->napi);
 		} else {
-			int pkts;
-
-			pkts = m_can_rx_handler(dev, NAPI_POLL_WEIGHT, ir);
-			if (pkts < 0)
-				goto out_fail;
+			ret = m_can_rx_handler(dev, NAPI_POLL_WEIGHT, ir);
+			if (ret < 0)
+				return ret;
 		}
 	}
 
@@ -1254,8 +1256,9 @@ static irqreturn_t m_can_isr(int irq, void *dev_id)
 	} else  {
 		if (ir & (IR_TEFN | IR_TEFW)) {
 			/* New TX FIFO Element arrived */
-			if (m_can_echo_tx_event(dev) != 0)
-				goto out_fail;
+			ret = m_can_echo_tx_event(dev);
+			if (ret != 0)
+				return ret;
 		}
 	}
 
@@ -1263,16 +1266,31 @@ static irqreturn_t m_can_isr(int irq, void *dev_id)
 		can_rx_offload_threaded_irq_finish(&cdev->offload);
 
 	return IRQ_HANDLED;
+}
 
-out_fail:
-	m_can_disable_all_interrupts(cdev);
-	return IRQ_HANDLED;
+static irqreturn_t m_can_isr(int irq, void *dev_id)
+{
+	struct net_device *dev = (struct net_device *)dev_id;
+	struct m_can_classdev *cdev = netdev_priv(dev);
+	int ret;
+
+	ret =  m_can_interrupt_handler(cdev);
+	if (ret < 0) {
+		m_can_disable_all_interrupts(cdev);
+		return IRQ_HANDLED;
+	}
+
+	return ret;
 }
 
 static enum hrtimer_restart m_can_coalescing_timer(struct hrtimer *timer)
 {
 	struct m_can_classdev *cdev = container_of(timer, struct m_can_classdev, hrtimer);
 
+	if (cdev->can.state == CAN_STATE_BUS_OFF ||
+	    cdev->can.state == CAN_STATE_STOPPED)
+		return HRTIMER_NORESTART;
+
 	irq_wake_thread(cdev->net->irq, cdev->net);
 
 	return HRTIMER_NORESTART;
@@ -1973,8 +1991,17 @@ static enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
 {
 	struct m_can_classdev *cdev = container_of(timer, struct
 						   m_can_classdev, hrtimer);
+	int ret;
+
+	if (cdev->can.state == CAN_STATE_BUS_OFF ||
+	    cdev->can.state == CAN_STATE_STOPPED)
+		return HRTIMER_NORESTART;
+
+	ret = m_can_interrupt_handler(cdev);
 
-	m_can_isr(0, cdev->net);
+	/* On error or if napi is scheduled to read, stop the timer */
+	if (ret < 0 || napi_is_scheduled(&cdev->napi))
+		return HRTIMER_NORESTART;
 
 	hrtimer_forward_now(timer, ms_to_ktime(HRTIMER_POLL_INTERVAL_MS));