RE: [PATCH v2] can: m_can: add support for handling arbitration error

[pankj.sharma]

> From: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
> 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@xxxxxxxxxxx>
> > Signed-off-by: Sriram Dash <sriram.dash@xxxxxxxxxxx>
> > ---
> >
> > 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.

Alright. We shall handle the stats even when skb fails. 
Shall post in upcoming revision.

> 
> > +		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
> 
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