can: m_can: m_can_handle_bus_errors(): add support for handling DLEC error on CAN-FD frames

When a frame in CAN FD format has reached the data phase, the next CAN
event (error or valid frame) will be shown in DLEC.

Utilize the dedicated flag (Data Phase Last Error Code: DLEC flag) to
determine the type of last error that occurred in the data phase of a
CAN-FD frame and handle the bus errors.
Signed-off-by: Vivek Yadav <vivek.2311@samsung.com>
Link: https://lore.kernel.org/all/20221018081934.1336690-1-mkl@pengutronix.deReviewed-by: Chandrasekar Ramakrishnan <rcsekar@samsung.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -156,6 +156,7 @@ enum m_can_reg {
 #define PSR_EW		BIT(6)
 #define PSR_EP		BIT(5)
 #define PSR_LEC_MASK	GENMASK(2, 0)
+#define PSR_DLEC_MASK	GENMASK(10, 8)
 
 /* Interrupt Register (IR) */
 #define IR_ALL_INT	0xffffffff
@@ -875,11 +876,19 @@ static int m_can_handle_bus_errors(struct net_device *dev, u32 irqstatus,
 	/* handle lec errors on the bus */
 	if (cdev->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) {
 		u8 lec = FIELD_GET(PSR_LEC_MASK, psr);
+		u8 dlec = FIELD_GET(PSR_DLEC_MASK, psr);
 
-		if (is_lec_err(lec))
+		if (is_lec_err(lec)) {
+			netdev_dbg(dev, "Arbitration phase error detected\n");
 			work_done += m_can_handle_lec_err(dev, lec);
 		}
 		
+		if (is_lec_err(dlec)) {
+			netdev_dbg(dev, "Data phase error detected\n");
+			work_done += m_can_handle_lec_err(dev, dlec);
+		}
+	}
+
 	/* handle protocol errors in arbitration phase */
 	if ((cdev->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) &&
 	    m_can_is_protocol_err(irqstatus))