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.

Reviewed-by: Markus Schneider-Pargmann <msp@baylibre.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.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 4451ea750b74..0b622248e229 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;

-- 
2.51.0