can: rcar_can: Mailbox bitfield conversion

Convert CAN Mailbox Register field accesses to use the FIELD_PREP() and
FIELD_GET() bitfield access macro.

This gets rid of explicit shifts, and keeps a clear separation between
hardware register layouts and offical CAN definitions.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/c75c7d6ed5929c4becf7c9178cec04a0731e8ab1.1755857536.git.geert+renesas@glider.be
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Author: geertu

drivers/net/can/rcar/rcar_can.c

@@ -160,7 +160,8 @@ static const struct can_bittiming_const rcar_can_bittiming_const = {
 /* Mailbox and Mask Registers bits */
 #define RCAR_CAN_IDE		BIT(31)		/* ID Extension */
 #define RCAR_CAN_RTR		BIT(30)		/* Remote Transmission Request */
-#define RCAR_CAN_SID_SHIFT	18
+#define RCAR_CAN_SID		GENMASK(28, 18)	/* Standard ID */
+#define RCAR_CAN_EID		GENMASK(28, 0)	/* Extended ID */
 
 /* Mailbox Interrupt Enable Register 1 bits */
 #define RCAR_CAN_MIER1_RXFIE	BIT(28)		/* Receive  FIFO Interrupt Enable */
@@ -599,9 +600,10 @@ static netdev_tx_t rcar_can_start_xmit(struct sk_buff *skb,
 		return NETDEV_TX_OK;
 
 	if (cf->can_id & CAN_EFF_FLAG)	/* Extended frame format */
-		data = (cf->can_id & CAN_EFF_MASK) | RCAR_CAN_IDE;
+		data = FIELD_PREP(RCAR_CAN_EID, cf->can_id & CAN_EFF_MASK) |
+		       RCAR_CAN_IDE;
 	else				/* Standard frame format */
-		data = (cf->can_id & CAN_SFF_MASK) << RCAR_CAN_SID_SHIFT;
+		data = FIELD_PREP(RCAR_CAN_SID, cf->can_id & CAN_SFF_MASK);
 
 	if (cf->can_id & CAN_RTR_FLAG) { /* Remote transmission request */
 		data |= RCAR_CAN_RTR;
@@ -656,9 +658,9 @@ static void rcar_can_rx_pkt(struct rcar_can_priv *priv)
 
 	data = readl(&priv->regs->mb[RCAR_CAN_RX_FIFO_MBX].id);
 	if (data & RCAR_CAN_IDE)
-		cf->can_id = (data & CAN_EFF_MASK) | CAN_EFF_FLAG;
+		cf->can_id = FIELD_GET(RCAR_CAN_EID, data) | CAN_EFF_FLAG;
 	else
-		cf->can_id = (data >> RCAR_CAN_SID_SHIFT) & CAN_SFF_MASK;
+		cf->can_id = FIELD_GET(RCAR_CAN_SID, data);
 
 	dlc = readb(&priv->regs->mb[RCAR_CAN_RX_FIFO_MBX].dlc);
 	cf->len = can_cc_dlc2len(dlc);