From: Marc Kleine-Budde <mkl@pengutronix.de>
Date: Wed, 6 Aug 2025 16:56:15 +0200
Subject: [PATCH] can: m_can: m_can_handle_state_errors(): fix CAN state
 transition to Error Active

The CAN Error State is determined by the receive and transmit error
counters. The CAN error counters decrease when reception/transmission
is successful, so that a status transition back to the Error Active
status is possible. This transition is not handled by
m_can_handle_state_errors().

Add the missing detection of the Error Active state to
m_can_handle_state_errors() and extend the handling of this state in
m_can_handle_state_change().

Fixes: e0d1f4816f2a ("can: m_can: add Bosch M_CAN controller support")
Fixes: cd0d83eab2e0 ("can: m_can: m_can_handle_state_change(): fix state change")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Upstream-Status: Submitted [https://lore.kernel.org/all/20250812-m_can-fix-state-handling-v1-0-b739e06c0a3b@pengutronix.de]
---
 drivers/net/can/m_can/m_can.c | 48 ++++++++++++++++++++++++++-----------------
 1 file changed, 29 insertions(+), 19 deletions(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index a51dc0bb8124..b485d2f3d971 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -812,6 +812,10 @@ static int m_can_handle_state_change(struct net_device *dev,
 	u32 timestamp = 0;
 
 	switch (new_state) {
+	case CAN_STATE_ERROR_ACTIVE:
+		/* error active state */
+		cdev->can.state = CAN_STATE_ERROR_ACTIVE;
+		break;
 	case CAN_STATE_ERROR_WARNING:
 		/* error warning state */
 		cdev->can.can_stats.error_warning++;
@@ -841,6 +845,13 @@ static int m_can_handle_state_change(struct net_device *dev,
 	__m_can_get_berr_counter(dev, &bec);
 
 	switch (new_state) {
+	case CAN_STATE_ERROR_ACTIVE:
+		/* error active state */
+		cf->can_id |= CAN_ERR_CRTL | CAN_ERR_CNT;
+		cf->data[1] = CAN_ERR_CRTL_ACTIVE;
+		cf->data[6] = bec.txerr;
+		cf->data[7] = bec.rxerr;
+		break;
 	case CAN_STATE_ERROR_WARNING:
 		/* error warning state */
 		cf->can_id |= CAN_ERR_CRTL | CAN_ERR_CNT;
@@ -877,30 +888,29 @@ static int m_can_handle_state_change(struct net_device *dev,
 	return 1;
 }
 
-static int m_can_handle_state_errors(struct net_device *dev, u32 psr)
+static enum can_state
+m_can_can_state_get_by_psr(const u32 psr)
 {
-	struct m_can_classdev *cdev = netdev_priv(dev);
-	int work_done = 0;
+	if (psr & PSR_BO)
+		return CAN_STATE_BUS_OFF;
+	if (psr & PSR_EP)
+		return CAN_STATE_ERROR_PASSIVE;
+	if (psr & PSR_EW)
+		return CAN_STATE_ERROR_WARNING;
 
-	if (psr & PSR_EW && cdev->can.state != CAN_STATE_ERROR_WARNING) {
-		netdev_dbg(dev, "entered error warning state\n");
-		work_done += m_can_handle_state_change(dev,
-						       CAN_STATE_ERROR_WARNING);
-	}
+	return CAN_STATE_ERROR_ACTIVE;
+}
 
-	if (psr & PSR_EP && cdev->can.state != CAN_STATE_ERROR_PASSIVE) {
-		netdev_dbg(dev, "entered error passive state\n");
-		work_done += m_can_handle_state_change(dev,
-						       CAN_STATE_ERROR_PASSIVE);
-	}
+static int m_can_handle_state_errors(struct net_device *dev, u32 psr)
+{
+	struct m_can_classdev *cdev = netdev_priv(dev);
+	enum can_state new_state;
 
-	if (psr & PSR_BO && cdev->can.state != CAN_STATE_BUS_OFF) {
-		netdev_dbg(dev, "entered error bus off state\n");
-		work_done += m_can_handle_state_change(dev,
-						       CAN_STATE_BUS_OFF);
-	}
+	new_state = m_can_can_state_get_by_psr(psr);
+	if (new_state == cdev->can.state)
+		return 0;
 
-	return work_done;
+	return m_can_handle_state_change(dev, new_state);
 }
 
 static void m_can_handle_other_err(struct net_device *dev, u32 irqstatus)