RE: [RESEND] [PATCH 1/1] can: m_can: Control tx and rx flow to avoid communication stall

[Kumari Pallavi]

Hi,

> -----Original Message-----
> From: Kumari Pallavi <kumari.pallavi@xxxxxxxxx>
> Sent: Friday, June 23, 2023 2:29 PM
> To: rcsekar@xxxxxxxxxxx; wg@xxxxxxxxxxxxxx; mkl@xxxxxxxxxxxxxx;
> davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx;
> pabeni@xxxxxxxxxx
> Cc: Sangannavar, Mallikarjunappa <mallikarjunappa.sangannavar@xxxxxxxxx>;
> Nikula, Jarkko <jarkko.nikula@xxxxxxxxx>; linux-can@xxxxxxxxxxxxxxx;
> netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Kumari Pallavi
> <kumari.pallavi@xxxxxxxxx>; Thokala, Srikanth <srikanth.thokala@xxxxxxxxx>
> Subject: [RESEND] [PATCH 1/1] can: m_can: Control tx and rx flow to avoid
> communication stall
> 
> In bi-directional CAN transfer using M_CAN IP, with the frame gap being set to
> '0', it leads to Protocol error in Arbitration phase resulting in communication
> stall.
> Discussed with Bosch M_CAN IP team and the stall issue can only be overcome
> by controlling the tx and rx packets flow as done by the patch.
> 
> Rx packets would also be serviced when there is a tx interrupt. The solution has
> been tested extensively for more than 10 days, and no issues has been observed.
> 
> Setup that is used to reproduce the issue:
> 
> +---------------------+		+----------------------+
> |Intel ElkhartLake    |		|Intel ElkhartLake     |
> |	+--------+    |		|	+--------+     |
> |	|m_can 0 |    |<=======>|	|m_can 0 |     |
> |	+--------+    |		|	+--------+     |
> +---------------------+		+----------------------+
> 
> Steps to be run on the two Elkhartlake HW:
> 
> 1. ip link set can0 type can bitrate 1000000 2. ip link set can0 txqueuelen 2048 3.
> ip link set can0 up 4. cangen -g 0 can0 5. candump can0
> 
> cangen -g 0 can0 & candump can0 commands are used for transmit and receive
> on both the m_can HW simultaneously where -g is the frame gap between two
> frames.
> 
> Signed-off-by: Kumari Pallavi <kumari.pallavi@xxxxxxxxx>
> Signed-off-by: Srikanth Thokala <srikanth.thokala@xxxxxxxxx>
> ---
>  drivers/net/can/m_can/m_can.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index a5003435802b..94aa0ba89202 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -1118,7 +1118,7 @@ static irqreturn_t m_can_isr(int irq, void *dev_id)
>  			/* New TX FIFO Element arrived */
>  			if (m_can_echo_tx_event(dev) != 0)
>  				goto out_fail;
> -
> +			m_can_write(cdev, M_CAN_IE, IR_ALL_INT &
> ~(IR_TEFN));
>  			if (netif_queue_stopped(dev) &&
>  			    !m_can_tx_fifo_full(cdev))
>  				netif_wake_queue(dev);
> @@ -1787,6 +1787,7 @@ static netdev_tx_t m_can_start_xmit(struct sk_buff
> *skb,
>  		}
>  	} else {
>  		cdev->tx_skb = skb;
> +		m_can_write(cdev, M_CAN_IE, IR_ALL_INT & (IR_TEFN));
>  		return m_can_tx_handler(cdev);
>  	}
> 

Kindly review the patch and please let us know if any comments!

Thanks,
Pallavi
> --
> 2.17.1