[PATCH v5 13/16] can: grcan: Add CANFD TX support alongside legacy CAN
From: Arun Muthusamy
Date: Mon Feb 16 2026 - 09:00:33 EST
Include CANFD TX support with the legacy CAN support, enabling
support for extended data payloads to provide higher bit rates.
Signed-off-by: Arun Muthusamy <arun.muthusamy@xxxxxxxxxxx>
---
drivers/net/can/grcan.c | 111 ++++++++++++++++++++++++++++++----------
1 file changed, 85 insertions(+), 26 deletions(-)
diff --git a/drivers/net/can/grcan.c b/drivers/net/can/grcan.c
index 28fa219e1c3b..ae9f6fd4c8bf 100644
--- a/drivers/net/can/grcan.c
+++ b/drivers/net/can/grcan.c
@@ -196,6 +196,10 @@ struct grcan_registers {
#define GRCAN_MSG_OFF 0x00000002
#define GRCAN_MSG_PASS 0x00000001
+#define GRCAN_MSG_EID_MASK GENMASK(28, 0)
+#define GRCAN_MSG_BID_MASK GENMASK(28, 18)
+#define GRCAN_MSG_DLC_MASK GENMASK(31, 28)
+
#define GRCAN_BUFFER_ALIGNMENT 1024
#define GRCAN_DEFAULT_BUFFER_SIZE 1024
#define GRCAN_VALID_TR_SIZE_MASK 0x001fffc0
@@ -228,6 +232,9 @@ struct grcan_registers {
#define GRCANFD_FDBTR_PS2_BIT 5
#define GRCANFD_FDBTR_SJW_BIT 0
+#define GRCAN_TX_BRS BIT(25)
+#define GRCAN_TX_FDF BIT(26)
+
/* Hardware capabilities */
struct grcan_hwcap {
/* CAN-FD capable, indicates GRCANFD IP.
@@ -1222,6 +1229,19 @@ static void grcan_transmit_catch_up(struct net_device *dev)
spin_unlock_irqrestore(&priv->lock, flags);
}
+static int grcan_numbds(int len)
+{
+ if (len <= GRCAN_CLASSIC_DATA_SIZE)
+ return 1;
+
+ return 1 + DIV_ROUND_UP(len - GRCAN_CLASSIC_DATA_SIZE, GRCAN_MSG_SIZE);
+}
+
+static inline union grcan_msg_slot *grcan_tx_msg_slot(struct grcan_dma *dma, u32 off)
+{
+ return (union grcan_msg_slot *)((u8 *)dma->tx.msg_slot + off);
+}
+
static int grcan_receive(struct net_device *dev, int budget)
{
struct grcan_priv *priv = netdev_priv(dev);
@@ -1404,15 +1424,23 @@ static netdev_tx_t grcan_start_xmit(struct sk_buff *skb,
struct net_device *dev)
{
struct grcan_priv *priv = netdev_priv(dev);
- struct grcan_registers __iomem *regs = priv->regs;
+ struct grcan_registers __iomem *regs;
+ u32 eff, rtr, dlc, tmp, err, can_id;
struct grcan_dma *dma = &priv->dma;
- struct can_frame *cf = (struct can_frame *)skb->data;
+ u32 bds, copy_len, payload_offset;
u32 id, txwr, txrd, space, txctrl;
- int slotindex;
- u32 *slot;
- u32 rtr, eff, dlc, tmp, err;
+ union grcan_msg_slot *msg;
+ struct canfd_frame *cfd;
+ struct can_frame *cf;
unsigned long flags;
- u32 oneshotmode = priv->can.ctrlmode & CAN_CTRLMODE_ONE_SHOT;
+ u32 oneshotmode;
+ int slotindex;
+ u8 *payload;
+ u8 len;
+ int i;
+
+ regs = priv->regs;
+ oneshotmode = priv->can.ctrlmode & CAN_CTRLMODE_ONE_SHOT;
if (can_dev_dropped_skb(dev, skb))
return NETDEV_TX_OK;
@@ -1423,6 +1451,18 @@ static netdev_tx_t grcan_start_xmit(struct sk_buff *skb,
if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
return NETDEV_TX_BUSY;
+ cfd = (struct canfd_frame *)skb->data;
+ len = cfd->len;
+ can_id = cfd->can_id;
+ payload = cfd->data;
+
+ if (can_is_canfd_skb(skb)) {
+ dlc = can_fd_len2dlc(len);
+ } else {
+ cf = (struct can_frame *)skb->data;
+ dlc = can_get_cc_dlc(cf, priv->can.ctrlmode);
+ }
+
/* Reads of priv->eskbp and shut-downs of the queue needs to
* be atomic towards the updates to priv->eskbp and wake-ups
* of the queue in the interrupt handler.
@@ -1433,7 +1473,7 @@ static netdev_tx_t grcan_start_xmit(struct sk_buff *skb,
space = grcan_txspace(dma->tx.size, txwr, priv->eskbp);
slotindex = txwr / GRCAN_MSG_SIZE;
- slot = (u32 *)((u8 *)dma->tx.msg_slot + txwr);
+ bds = grcan_numbds(len);
if (unlikely(space == 1))
netif_stop_queue(dev);
@@ -1449,24 +1489,44 @@ static netdev_tx_t grcan_start_xmit(struct sk_buff *skb,
return NETDEV_TX_BUSY;
}
- /* Convert and write CAN message to DMA buffer */
- eff = cf->can_id & CAN_EFF_FLAG;
- rtr = cf->can_id & CAN_RTR_FLAG;
- id = cf->can_id & (eff ? CAN_EFF_MASK : CAN_SFF_MASK);
- dlc = cf->len;
- if (eff)
- tmp = (id << GRCAN_MSG_EID_BIT) & GRCAN_MSG_EID;
- else
- tmp = (id << GRCAN_MSG_BID_BIT) & GRCAN_MSG_BID;
- slot[0] = (eff ? GRCAN_MSG_IDE : 0) | (rtr ? GRCAN_MSG_RTR : 0) | tmp;
+ msg = grcan_tx_msg_slot(dma, txwr);
+ memset(msg, 0, sizeof(*msg));
+
+ eff = can_id & CAN_EFF_FLAG;
+ rtr = can_id & CAN_RTR_FLAG;
+ id = can_id & (eff ? CAN_EFF_MASK : CAN_SFF_MASK);
+
+ tmp = eff ? FIELD_PREP(GRCAN_MSG_EID_MASK, id)
+ : FIELD_PREP(GRCAN_MSG_BID_MASK, id);
+
+ msg->header.id = (eff ? GRCAN_MSG_IDE : 0) |
+ (rtr ? GRCAN_MSG_RTR : 0) |
+ tmp;
- slot[1] = ((dlc << GRCAN_MSG_DLC_BIT) & GRCAN_MSG_DLC);
- slot[2] = 0;
- slot[3] = 0;
- if (dlc > 0)
- memcpy(&slot[2], cf->data, sizeof(u32));
- if (dlc > 4)
- memcpy(&slot[3], cf->data + 4, sizeof(u32));
+ msg->header.ctrl = FIELD_PREP(GRCAN_MSG_DLC_MASK, dlc);
+
+ if (can_is_canfd_skb(skb)) {
+ msg->header.ctrl |= GRCAN_TX_FDF;
+ if (cfd->flags & CANFD_BRS)
+ msg->header.ctrl |= GRCAN_TX_BRS;
+ }
+
+ copy_len = min_t(u32, len, GRCAN_CLASSIC_DATA_SIZE);
+ memcpy(msg->header.data, payload, copy_len);
+ payload_offset = copy_len;
+
+ txwr = grcan_ring_add(txwr, GRCAN_MSG_SIZE, dma->tx.size);
+
+ for (i = 1; i < bds; i++) {
+ msg = grcan_tx_msg_slot(dma, txwr);
+
+ memset(msg, 0, sizeof(*msg));
+ copy_len = min_t(u32, (u32)len - payload_offset, (u32)GRCAN_MSG_SIZE);
+ memcpy(msg->frags.data, payload + payload_offset, copy_len);
+ payload_offset += copy_len;
+
+ txwr = grcan_ring_add(txwr, GRCAN_MSG_SIZE, dma->tx.size);
+ }
/* Checking that channel has not been disabled. These cases
* should never happen
@@ -1508,8 +1568,7 @@ static netdev_tx_t grcan_start_xmit(struct sk_buff *skb,
wmb();
/* Update write pointer to start transmission */
- grcan_write_reg(®s->txwr,
- grcan_ring_add(txwr, GRCAN_MSG_SIZE, dma->tx.size));
+ grcan_write_reg(®s->txwr, txwr);
return NETDEV_TX_OK;
}
--
2.51.0