Re: [PATCH v1 4/9] can: Add Nuvoton NCT6694 CAN support

Marc Kleine-Budde
2024-10-24T12:13:29Z

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Hello,

thanks for your contribution. It seems to me that there is no proper
TX-flow control and I have some questions.

On 24.10.2024 16:59:17, Ming Yu wrote:

[...]

> +static netdev_tx_t nct6694_canfd_start_xmit(struct sk_buff *skb,
> + struct net_device *ndev)
> +{
> + struct nct6694_canfd_priv *priv = netdev_priv(ndev);
> + struct nct6694 *nct6694 = priv->nct6694;
> + struct canfd_frame *cf = (struct canfd_frame *)skb->data;
> + struct net_device_stats *stats = &ndev->stats;
> + int can_idx = priv->can_idx;
> + u32 txid = 0;
> + int i;
> + unsigned int echo_byte;
> + u8 data_buf[REQUEST_CAN_CMD10_LEN] = {0};
> +
> + if (can_dropped_invalid_skb(ndev, skb))
> + return NETDEV_TX_OK;
> +
> + /*
> + * No check for NCT66794 because the TX bit is read-clear
> + * and may be read-cleared by other function
> + * Just check the result of tx command.
> + */

Where do you check the result of the TX command?

> + /* Check if the TX buffer is full */

Where's the check if the TX buffer is full?

> + netif_stop_queue(ndev);
> +
> + if (can_idx == 0)
> + data_buf[CAN_TAG_IDX] = CAN_TAG_CAN0;
> + else
> + data_buf[CAN_TAG_IDX] = CAN_TAG_CAN1;
> +
> + if (cf->can_id & CAN_EFF_FLAG) {
> + txid = cf->can_id & CAN_EFF_MASK;
> + /*
> + * In case the Extended ID frame is transmitted, the
> + * standard and extended part of the ID are swapped
> + * in the register, so swap them back to send the
> + * correct ID.
> + */
> + data_buf[CAN_FLAG_IDX] |= CAN_FLAG_EFF;
> + } else {
> + txid = cf->can_id & CAN_SFF_MASK;
> + }
> +
> + set_buf32(&data_buf[CAN_ID_IDX], txid);
> +
> + data_buf[CAN_DLC_IDX] = cf->len;
> +
> + if ((priv->can.ctrlmode & CAN_CTRLMODE_FD) && can_is_canfd_skb(skb)) {
> + data_buf[CAN_FLAG_IDX] |= CAN_FLAG_FD;
> + if (cf->flags & CANFD_BRS)
> + data_buf[CAN_FLAG_IDX] |= CAN_FLAG_BRS;
> + }
> +
> + if (cf->can_id & CAN_RTR_FLAG)
> + data_buf[CAN_FLAG_IDX] |= CAN_FLAG_RTR;
> +
> + /* set data to buf */
> + for (i = 0; i < cf->len; i++)
> + data_buf[CAN_DATA_IDX + i] = *(u8 *)(cf->data + i);
> +
> + can_put_echo_skb(skb, ndev, 0, 0);
> +
> + memcpy(priv->data_buf, data_buf, REQUEST_CAN_CMD10_LEN);
> + queue_work(nct6694->async_workqueue, &priv->tx_work);
> +
> + stats->tx_bytes += cf->len;
> + stats->tx_packets++;
> + echo_byte = can_get_echo_skb(ndev, 0, NULL);
> +
> + netif_wake_queue(ndev);

How do you make sure that the tx_work has finished?
Once you wake the queue, the xmit function can be called again. If your
tx_work has not finished, you'll overwrite the priv->data_buf.

> +
> + return NETDEV_TX_OK;
> +}
> +
> +static void nct6694_canfd_tx_work(struct work_struct *work)
> +{
> + struct nct6694_canfd_priv *priv;
> +
> + priv = container_of(work, struct nct6694_canfd_priv, tx_work);
> +
> + nct6694_write_msg(priv->nct6694, REQUEST_CAN_MOD,
> + REQUEST_CAN_CMD10_OFFSET(1),
> + REQUEST_CAN_CMD10_LEN,
> + priv->data_buf);
> +}

Marc

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Embedded Linux | https://www.pengutronix.de |
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