The TX DLC, the transmission length information, was not written
into the transmit configuration register. When using the CAN core
with different CAN controller, the receiving CAN controller will
receive only the ID part of the CAN frame, but no data at all.

This patch adds the TX DLC into the register to fix this issue.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: Wolfgang Grandegger <redacted>
---
V2: - Use can_len2dlc() unconditionally to sanitize DLC in the TX path
    - The CAN_CTRLMODE_CANFD_NON_ISO can only ever be set if the
      CANFD_CTRLMODE_CANFD is set. Use only the later for checking
      if the core transmits in CANFD mode.
V3: Drop u32 txdlc = 0;, make it just u32 txdlc; and init txdlc in place
    with txdlc = can_len2dlc(); instead of doing txdlc |= can_len2dlc();
V4: none
---
 drivers/net/can/ifi_canfd/ifi_canfd.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/net/can/ifi_canfd/ifi_canfd.c b/drivers/net/can/ifi_canfd/ifi_canfd.c
index 86287a3..c905bfa 100644
--- a/drivers/net/can/ifi_canfd/ifi_canfd.c
+++ b/drivers/net/can/ifi_canfd/ifi_canfd.c

@@ -749,8 +749,7 @@ static netdev_tx_t ifi_canfd_start_xmit(struct sk_buff *skb,
 {
 	struct ifi_canfd_priv *priv = netdev_priv(ndev);
 	struct canfd_frame *cf = (struct canfd_frame *)skb->data;
-	u32 txst, txid;
-	u32 txdlc = 0;
+	u32 txst, txid, txdlc;
 	int i;
 
 	if (can_dropped_invalid_skb(ndev, skb))

@@ -773,12 +772,11 @@ static netdev_tx_t ifi_canfd_start_xmit(struct sk_buff *skb,
 		txid = cf->can_id & CAN_SFF_MASK;
 	}
 
-	if (priv->can.ctrlmode & (CAN_CTRLMODE_FD | CAN_CTRLMODE_FD_NON_ISO)) {
-		if (can_is_canfd_skb(skb)) {
-			txdlc |= IFI_CANFD_TXFIFO_DLC_EDL;
-			if (cf->flags & CANFD_BRS)
-				txdlc |= IFI_CANFD_TXFIFO_DLC_BRS;
-		}
+	txdlc = can_len2dlc(cf->len);
+	if ((priv->can.ctrlmode & CAN_CTRLMODE_FD) && can_is_canfd_skb(skb)) {
+		txdlc |= IFI_CANFD_TXFIFO_DLC_EDL;
+		if (cf->flags & CANFD_BRS)
+			txdlc |= IFI_CANFD_TXFIFO_DLC_BRS;
 	}
 
 	if (cf->can_id & CAN_RTR_FLAG)

-- 
2.7.0