can: c_can: D_CAN: c_can_chip_config(): perform a sofware reset on open

When the CAN interface is closed it the hardwre is put in power down
mode, but does not reset the error counters / state. Reset the D_CAN on
open, so the reported state and the actual state match.

According to [1], the C_CAN module doesn't have the software reset.

[1] http://www.bosch-semiconductors.com/media/ip_modules/pdf_2/c_can_fd8/users_manual_c_can_fd8_r210_1.pdfSigned-off-by: Jeroen Hofstee <jhofstee@victronenergy.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/c_can/c_can.c

@@ -52,6 +52,7 @@
 #define CONTROL_EX_PDR		BIT(8)
 
 /* control register */
+#define CONTROL_SWR		BIT(15)
 #define CONTROL_TEST		BIT(7)
 #define CONTROL_CCE		BIT(6)
 #define CONTROL_DISABLE_AR	BIT(5)
@@ -572,6 +573,26 @@ static void c_can_configure_msg_objects(struct net_device *dev)
 				   IF_MCONT_RCV_EOB);
 }
 
+static int c_can_software_reset(struct net_device *dev)
+{
+	struct c_can_priv *priv = netdev_priv(dev);
+	int retry = 0;
+
+	if (priv->type != BOSCH_D_CAN)
+		return 0;
+
+	priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_SWR | CONTROL_INIT);
+	while (priv->read_reg(priv, C_CAN_CTRL_REG) & CONTROL_SWR) {
+		msleep(20);
+		if (retry++ > 100) {
+			netdev_err(dev, "CCTRL: software reset failed\n");
+			return -EIO;
+		}
+	}
+
+	return 0;
+}
+
 /*
  * Configure C_CAN chip:
  * - enable/disable auto-retransmission
@@ -581,6 +602,11 @@ static void c_can_configure_msg_objects(struct net_device *dev)
 static int c_can_chip_config(struct net_device *dev)
 {
 	struct c_can_priv *priv = netdev_priv(dev);
+	int err;
+
+	err = c_can_software_reset(dev);
+	if (err)
+		return err;
 
 	/* enable automatic retransmission */
 	priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_ENABLE_AR);