can: m_can: add support for handling arbitration error

The Bosch MCAN hardware (3.1.0 and above) supports interrupt flag to
detect Protocol error in arbitration phase.

Transmit error statistics is currently not updated from the MCAN driver.
Protocol error in arbitration phase is a TX error and the network
statistics should be updated accordingly.

The member "tx_error" of "struct net_device_stats" should be incremented
as arbitration is a transmit protocol error. Also "arbitration_lost" of
"struct can_device_stats" should be incremented to report arbitration
lost.
Signed-off-by: Pankaj Sharma <pankj.sharma@samsung.com>
Signed-off-by: Sriram Dash <sriram.dash@samsung.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -778,6 +778,43 @@ static inline bool is_lec_err(u32 psr)
 	return psr && (psr != LEC_UNUSED);
 }
 
+static inline bool m_can_is_protocol_err(u32 irqstatus)
+{
+	return irqstatus & IR_ERR_LEC_31X;
+}
+
+static int m_can_handle_protocol_error(struct net_device *dev, u32 irqstatus)
+{
+	struct net_device_stats *stats = &dev->stats;
+	struct m_can_classdev *cdev = netdev_priv(dev);
+	struct can_frame *cf;
+	struct sk_buff *skb;
+
+	/* propagate the error condition to the CAN stack */
+	skb = alloc_can_err_skb(dev, &cf);
+
+	/* update tx error stats since there is protocol error */
+	stats->tx_errors++;
+
+	/* update arbitration lost status */
+	if (cdev->version >= 31 && (irqstatus & IR_PEA)) {
+		netdev_dbg(dev, "Protocol error in Arbitration fail\n");
+		cdev->can.can_stats.arbitration_lost++;
+		if (skb) {
+			cf->can_id |= CAN_ERR_LOSTARB;
+			cf->data[0] |= CAN_ERR_LOSTARB_UNSPEC;
+		}
+	}
+
+	if (unlikely(!skb)) {
+		netdev_dbg(dev, "allocation of skb failed\n");
+		return 0;
+	}
+	netif_receive_skb(skb);
+
+	return 1;
+}
+
 static int m_can_handle_bus_errors(struct net_device *dev, u32 irqstatus,
 				   u32 psr)
 {
@@ -792,6 +829,11 @@ static int m_can_handle_bus_errors(struct net_device *dev, u32 irqstatus,
 	    is_lec_err(psr))
 		work_done += m_can_handle_lec_err(dev, psr & LEC_UNUSED);
 
+	/* handle protocol errors in arbitration phase */
+	if ((cdev->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) &&
+	    m_can_is_protocol_err(irqstatus))
+		work_done += m_can_handle_protocol_error(dev, irqstatus);
+
 	/* other unproccessed error interrupts */
 	m_can_handle_other_err(dev, irqstatus);