linux-kernel - [PATCH 4/7] can: m_can: m_can_chip_config(): bring up interface in correct state

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Message-Id: <20250812-m_can-fix-state-handling-v1-4-b739e06c0a3b@pengutronix.de>
Date: Tue, 12 Aug 2025 19:36:54 +0200
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Chandrasekar Ramakrishnan <rcsekar@...sung.com>, 
 Vincent Mailhol <mailhol.vincent@...adoo.fr>, 
 Patrik Flykt <patrik.flykt@...ux.intel.com>, 
 Dong Aisheng <b29396@...escale.com>, Fengguang Wu <fengguang.wu@...el.com>, 
 Varka Bhadram <varkabhadram@...il.com>, Wu Bo <wubo.oduw@...il.com>, 
 Markus Schneider-Pargmann <msp@...libre.com>, 
 Philipp Zabel <p.zabel@...gutronix.de>
Cc: linux-can@...r.kernel.org, linux-kernel@...r.kernel.org, 
 kernel@...gutronix.de, Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH 4/7] can: m_can: m_can_chip_config(): bring up interface in
 correct state

In some SoCs (observed on the STM32MP15) the M_CAN IP core keeps the
CAN state and CAN error counters over an internal reset cycle. An
external reset is not always possible, due to the shared reset with
the other CAN core. This caused the core not always be in Error Active
state when bringing up the controller.

Instead of always setting the CAN state to Error Active in
m_can_chip_config(), fix this by reading and decoding the Protocol
Status Regitser (PSR) and set the CAN state accordingly.

Fixes: e0d1f4816f2a ("can: m_can: add Bosch M_CAN controller support")
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 drivers/net/can/m_can/m_can.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index b485d2f3d971..310a907cbb7e 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1607,6 +1607,7 @@ static int m_can_chip_config(struct net_device *dev)
 static int m_can_start(struct net_device *dev)
 {
 	struct m_can_classdev *cdev = netdev_priv(dev);
+	u32 reg_psr;
 	int ret;
 
 	/* basic m_can configuration */
@@ -1617,7 +1618,8 @@ static int m_can_start(struct net_device *dev)
 	netdev_queue_set_dql_min_limit(netdev_get_tx_queue(cdev->net, 0),
 				       cdev->tx_max_coalesced_frames);
 
-	cdev->can.state = CAN_STATE_ERROR_ACTIVE;
+	reg_psr = m_can_read(cdev, M_CAN_PSR);
+	cdev->can.state = m_can_can_state_get_by_psr(reg_psr);
 
 	m_can_enable_all_interrupts(cdev);
 

-- 
2.50.1