Revert "can: m_can: remove support for custom bit timing"

The timing limits specified by the Elkhart Lake CPU datasheets do not
match the defaults. Let's reintroduce the support for custom bit timings.

This reverts commit 0ddd83fb.

Link: https://lore.kernel.org/all/00c9e2596b1a548906921a574d4ef7a03c0dace0.1636967198.git.matthias.schiffer@ew.tq-group.comSigned-off-by: NMatthias Schiffer <matthias.schiffer@ew.tq-group.com>
Signed-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -1494,20 +1494,32 @@ static int m_can_dev_setup(struct m_can_classdev *cdev)
 	case 30:
 		/* CAN_CTRLMODE_FD_NON_ISO is fixed with M_CAN IP v3.0.x */
 		can_set_static_ctrlmode(dev, CAN_CTRLMODE_FD_NON_ISO);
-		cdev->can.bittiming_const = &m_can_bittiming_const_30X;
-		cdev->can.data_bittiming_const = &m_can_data_bittiming_const_30X;
+		cdev->can.bittiming_const = cdev->bit_timing ?
+			cdev->bit_timing : &m_can_bittiming_const_30X;
+
+		cdev->can.data_bittiming_const = cdev->data_timing ?
+			cdev->data_timing :
+			&m_can_data_bittiming_const_30X;
 		break;
 	case 31:
 		/* CAN_CTRLMODE_FD_NON_ISO is fixed with M_CAN IP v3.1.x */
 		can_set_static_ctrlmode(dev, CAN_CTRLMODE_FD_NON_ISO);
-		cdev->can.bittiming_const = &m_can_bittiming_const_31X;
-		cdev->can.data_bittiming_const = &m_can_data_bittiming_const_31X;
+		cdev->can.bittiming_const = cdev->bit_timing ?
+			cdev->bit_timing : &m_can_bittiming_const_31X;
+
+		cdev->can.data_bittiming_const = cdev->data_timing ?
+			cdev->data_timing :
+			&m_can_data_bittiming_const_31X;
 		break;
 	case 32:
 	case 33:
 		/* Support both MCAN version v3.2.x and v3.3.0 */
-		cdev->can.bittiming_const = &m_can_bittiming_const_31X;
-		cdev->can.data_bittiming_const = &m_can_data_bittiming_const_31X;
+		cdev->can.bittiming_const = cdev->bit_timing ?
+			cdev->bit_timing : &m_can_bittiming_const_31X;
+
+		cdev->can.data_bittiming_const = cdev->data_timing ?
+			cdev->data_timing :
+			&m_can_data_bittiming_const_31X;
 
 		cdev->can.ctrlmode_supported |=
 			(m_can_niso_supported(cdev) ?

drivers/net/can/m_can/m_can.h

@@ -85,6 +85,9 @@ struct m_can_classdev {
 	struct sk_buff *tx_skb;
 	struct phy *transceiver;
 
+	struct can_bittiming_const *bit_timing;
+	struct can_bittiming_const *data_timing;
+
 	struct m_can_ops *ops;
 
 	int version;