linux-kernel - [PATCH 6/7] can: m_can: m_can_get_berr_counter(): don't wake up controller if interface is down

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Message-Id: <20250812-m_can-fix-state-handling-v1-6-b739e06c0a3b@pengutronix.de>
Date: Tue, 12 Aug 2025 19:36:56 +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 6/7] can: m_can: m_can_get_berr_counter(): don't wake up
 controller if interface is down

If the interface is down, the CAN controller might be powered down,
the clock disabled, and/or it's external reset asserted.

Don't wake up the controller to read the CAN bus error counters, if
the interface is down.

Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 drivers/net/can/m_can/m_can.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 149f3a8b5f7e..c24ea0e5599f 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -790,6 +790,10 @@ static int m_can_get_berr_counter(const struct net_device *dev,
 	struct m_can_classdev *cdev = netdev_priv(dev);
 	int err;
 
+	/* Avoid waking up the controller if the interface is down */
+	if (!(dev->flags & IFF_UP))
+		return 0;
+
 	err = m_can_clk_start(cdev);
 	if (err)
 		return err;

-- 
2.50.1