linux-kernel - Re: [PATCH v2] can: m_can: add support for handling arbitration error

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Message-ID: <89d7b65f-e8cf-9241-5642-ab3446b464a5@pengutronix.de>
Date:   Tue, 29 Oct 2019 15:23:23 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Pankaj Sharma <pankj.sharma@...sung.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     wg@...ndegger.com, davem@...emloft.net,
        eugen.hristev@...rochip.com, ludovic.desroches@...rochip.com,
        pankaj.dubey@...sung.com, rcsekar@...sung.com,
        jhofstee@...tronenergy.com, simon.horman@...ronome.com,
        Sriram Dash <sriram.dash@...sung.com>
Subject: Re: [PATCH v2] can: m_can: add support for handling arbitration error

On 10/21/19 2:13 PM, Pankaj Sharma wrote:
> The Bosch MCAN hardware (3.1.0 and above) supports interrupt flag to
> detect Protocol error in arbitration phase.
> 
> Transmit error statistics is currently not updated from the MCAN driver.
> Protocol error in arbitration phase is a TX error and the network
> statistics should be updated accordingly.
> 
> The member "tx_error" of "struct net_device_stats" should be incremented
> as arbitration is a transmit protocol error. Also "arbitration_lost" of
> "struct can_device_stats" should be incremented to report arbitration
> lost.
> 
> Signed-off-by: Pankaj Sharma <pankj.sharma@...sung.com>
> Signed-off-by: Sriram Dash <sriram.dash@...sung.com>
> ---
> 
> changes in v2:
> - common m_can_ prefix for is_protocol_err function
> - handling stats even if the allocation of the skb fails
> - resolving build errors on net-next branch
> 
>  drivers/net/can/m_can/m_can.c | 37 +++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index 75e7490c4299..a736297a875f 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -778,6 +778,38 @@ static inline bool is_lec_err(u32 psr)
>  	return psr && (psr != LEC_UNUSED);
>  }
>  
> +static inline bool m_can_is_protocol_err(u32 irqstatus)
> +{
> +	return irqstatus & IR_ERR_LEC_31X;
> +}
> +
> +static int m_can_handle_protocol_error(struct net_device *dev, u32 irqstatus)
> +{
> +	struct net_device_stats *stats = &dev->stats;
> +	struct m_can_classdev *cdev = netdev_priv(dev);
> +	struct can_frame *cf;
> +	struct sk_buff *skb;
> +
> +	/* propagate the error condition to the CAN stack */
> +	skb = alloc_can_err_skb(dev, &cf);
> +	if (unlikely(!skb)) {
> +		netdev_dbg(dev, "allocation of skb failed\n");
> +		stats->tx_errors++;
> +		return 0;
> +	}
> +	if (cdev->version >= 31 && (irqstatus & IR_PEA)) {
> +		netdev_dbg(dev, "Protocol error in Arbitration fail\n");
> +		stats->tx_errors++;
> +		cdev->can.can_stats.arbitration_lost++;

If the skb allocation fails, you miss the stats here.

> +		cf->can_id |= CAN_ERR_LOSTARB;
> +		cf->data[0] |= CAN_ERR_LOSTARB_UNSPEC;
> +	}
> +
> +	netif_receive_skb(skb);
> +
> +	return 1;
> +}
> +
>  static int m_can_handle_bus_errors(struct net_device *dev, u32 irqstatus,
>  				   u32 psr)
>  {
> @@ -792,6 +824,11 @@ static int m_can_handle_bus_errors(struct net_device *dev, u32 irqstatus,
>  	    is_lec_err(psr))
>  		work_done += m_can_handle_lec_err(dev, psr & LEC_UNUSED);
>  
> +	/* handle protocol errors in arbitration phase */
> +	if ((cdev->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) &&
> +	    m_can_is_protocol_err(irqstatus))
> +		work_done += m_can_handle_protocol_error(dev, irqstatus);
> +
>  	/* other unproccessed error interrupts */
>  	m_can_handle_other_err(dev, irqstatus);

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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