[PATCH net 17/20] can: c_can: c_can_chip_config(): keep controller in init mode until bittiming is configured

[Marc Kleine-Budde <mkl@pengutronix.de>]

From: Lucas Martins Alves <lucas.alves@lumal21.com.br>

c_can_chip_config() was programming C_CAN_CTRL_REG without CONTROL_INIT,
which may allow the controller to become active before
c_can_set_bittiming() finishes.

That creates a short timing window where the peripheral can interact with
the bus using a different/default bitrate, potentially generating bus
errors and corrupting traffic.

Set CONTROL_INIT together with the control-mode writes in
c_can_chip_config() (normal, loopback and listen-only paths), so the
controller stays halted until bit timing is fully programmed.

This prevents transient bus disturbance during startup when the configured
bitrate differs from the active bus bitrate.

Signed-off-by: Lucas Martins Alves <lucas.alves@lumal21.com.br>
Link: https://patch.msgid.link/20260714164839.771123-1-lucas.alves@lumal21.com.br
Fixes: 881ff67ad450 ("can: c_can: Added support for Bosch C_CAN controller")
Cc: stable@kernel.org
[mkl: remove space before close parenthesis]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/c_can/c_can_main.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/can/c_can/c_can_main.c b/drivers/net/can/c_can/c_can_main.c
index 3702cac7fbf0..b3b321d9ce68 100644
--- a/drivers/net/can/c_can/c_can_main.c
+++ b/drivers/net/can/c_can/c_can_main.c
@@ -597,20 +597,20 @@ static int c_can_chip_config(struct net_device *dev)
 		return err;
 
 	/* enable automatic retransmission */
-	priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_ENABLE_AR);
+	priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_ENABLE_AR | CONTROL_INIT);
 
 	if ((priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) &&
 	    (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK)) {
 		/* loopback + silent mode : useful for hot self-test */
-		priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_TEST);
+		priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_TEST | CONTROL_INIT);
 		priv->write_reg(priv, C_CAN_TEST_REG, TEST_LBACK | TEST_SILENT);
 	} else if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK) {
 		/* loopback mode : useful for self-test function */
-		priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_TEST);
+		priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_TEST | CONTROL_INIT);
 		priv->write_reg(priv, C_CAN_TEST_REG, TEST_LBACK);
 	} else if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
 		/* silent mode : bus-monitoring mode */
-		priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_TEST);
+		priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_TEST | CONTROL_INIT);
 		priv->write_reg(priv, C_CAN_TEST_REG, TEST_SILENT);
 	}
 
-- 
2.53.0