linux-kernel - Re: [PATCH 06/12] can: kvaser_usb_leaf: Fix TX queue out of sync after restart

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Date:   Sat, 28 May 2022 09:35:50 +0200
From:   Jimmy Assarsson <extja@...ser.com>
To:     Anssi Hannula <anssi.hannula@...wise.fi>
Cc:     linux-can@...r.kernel.org, Marc Kleine-Budde <mkl@...gutronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/12] can: kvaser_usb_leaf: Fix TX queue out of sync
 after restart

On 5/16/22 15:47, Anssi Hannula wrote:
> The TX queue seems to be implicitly flushed by the hardware during
> bus-off or bus-off recovery, but the driver does not reset the TX
> bookkeeping.
> 
> Despite not resetting TX bookkeeping the driver still re-enables TX
> queue unconditionally, leading to "cannot find free context" /
> NETDEV_TX_BUSY errors if the TX queue was full at bus-off time.
> 
> Fix that by resetting TX bookkeeping on CAN restart.
> 
> Also, add an explicit queue flush in case some hardware versions do not
> do that implicitly.

See comment below regarding this.

> Tested with 0bfd:0124 Kvaser Mini PCI Express 2xHS FW 4.18.778.
> 
> Fixes: 080f40a6fa28 ("can: kvaser_usb: Add support for Kvaser CAN/USB devices")
> Signed-off-by: Anssi Hannula <anssi.hannula@...wise.fi>
> ---
>   drivers/net/can/usb/kvaser_usb/kvaser_usb.h      | 2 ++
>   drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c | 2 +-
>   drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c | 6 ++++++
>   3 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/can/usb/kvaser_usb/kvaser_usb.h b/drivers/net/can/usb/kvaser_usb/kvaser_usb.h
> index 3a49257f9fa6..f1bea13a3829 100644
> --- a/drivers/net/can/usb/kvaser_usb/kvaser_usb.h
> +++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb.h
> @@ -175,6 +175,8 @@ struct kvaser_usb_dev_cfg {
>   extern const struct kvaser_usb_dev_ops kvaser_usb_hydra_dev_ops;
>   extern const struct kvaser_usb_dev_ops kvaser_usb_leaf_dev_ops;
>   
> +void kvaser_usb_unlink_tx_urbs(struct kvaser_usb_net_priv *priv);
> +
>   int kvaser_usb_recv_cmd(const struct kvaser_usb *dev, void *cmd, int len,
>   			int *actual_len);
>   
> diff --git a/drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c b/drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c
> index 7388fdca9079..a8d72fb8291a 100644
> --- a/drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c
> +++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c
> @@ -440,7 +440,7 @@ static void kvaser_usb_reset_tx_urb_contexts(struct kvaser_usb_net_priv *priv)
>   /* This method might sleep. Do not call it in the atomic context
>    * of URB completions.
>    */
> -static void kvaser_usb_unlink_tx_urbs(struct kvaser_usb_net_priv *priv)
> +void kvaser_usb_unlink_tx_urbs(struct kvaser_usb_net_priv *priv)
>   {
>   	usb_kill_anchored_urbs(&priv->tx_submitted);
>   	kvaser_usb_reset_tx_urb_contexts(priv);
> diff --git a/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c b/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
> index d7f2d64a8083..2d30a662edb5 100644
> --- a/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
> +++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
> @@ -1402,6 +1402,12 @@ static int kvaser_usb_leaf_set_mode(struct net_device *netdev,
>   
>   	switch (mode) {
>   	case CAN_MODE_START:
> +		err = kvaser_usb_leaf_flush_queue(priv);

All affected devices, leaf and usbcanII, will flush the Tx queue when
receiving CMD_START_CHIP.
So this is superfluous, and can be removed.

> +		if (err)
> +			return err;
> +
> +		kvaser_usb_unlink_tx_urbs(priv);
> +
>   		err = kvaser_usb_leaf_simple_cmd_async(priv, CMD_START_CHIP);
>   		if (err)
>   			return err;