RE: [PATCH v2] can: mcan: Add support for handling DLEC error on CAN FD

[Vivek Yadav]

> -----Original Message-----
> From: Marc Kleine-Budde [mailto:mkl@xxxxxxxxxxxxxx]
> Sent: 14 October 2022 12:41
> To: Vivek Yadav <vivek.2311@xxxxxxxxxxx>
> Cc: rcsekar@xxxxxxxxxxx; wg@xxxxxxxxxxxxxx; davem@xxxxxxxxxxxxx;
> edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx;
> pankaj.dubey@xxxxxxxxxxx; ravi.patel@xxxxxxxxxxx; linux-
> can@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2] can: mcan: Add support for handling DLEC error on
> CAN FD
> 
> On 14.10.2022 10:33:32, Vivek Yadav wrote:
> > When a frame in CAN FD format has reached the data phase, the next CAN
> > event (error or valid frame) will be shown in DLEC.
> >
> > Utilizes the dedicated flag (Data Phase Last Error Code: DLEC flag) to
> > determine the type of last error that occurred in the data phase of a
> > CAN FD frame and handle the bus errors.
> >
> > Signed-off-by: Vivek Yadav <vivek.2311@xxxxxxxxxxx>
> > ---
> > This patch is dependent on following patch from Marc:
> > [1]:
> > https://lore.kernel.org/all/20221012074205.691384-1-mkl@xxxxxxxxxxxxxx
> > /
> >
> >  drivers/net/can/m_can/m_can.c | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/can/m_can/m_can.c
> > b/drivers/net/can/m_can/m_can.c index 18a138fdfa66..8cff1f274aab
> > 100644
> > --- a/drivers/net/can/m_can/m_can.c
> > +++ b/drivers/net/can/m_can/m_can.c
> > @@ -156,6 +156,7 @@ enum m_can_reg {
> >  #define PSR_EW		BIT(6)
> >  #define PSR_EP		BIT(5)
> >  #define PSR_LEC_MASK	GENMASK(2, 0)
> > +#define PSR_DLEC_MASK   GENMASK(8, 10)
> >
> >  /* Interrupt Register (IR) */
> >  #define IR_ALL_INT	0xffffffff
> > @@ -876,8 +877,16 @@ static int m_can_handle_bus_errors(struct
> net_device *dev, u32 irqstatus,
> >  	if (cdev->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) {
> >  		u8 lec = FIELD_GET(PSR_LEC_MASK, psr);
> >
> > -		if (is_lec_err(lec))
> > +		if (is_lec_err(lec)) {
> >  			work_done += m_can_handle_lec_err(dev, lec);
> > +		} else {
> 
> In case of high interrupt latency there might be lec and dlec errors pending.
> As this is error handling and not the hot path, please check for both, i.e.:
Okay will do that.
> 
>                 if (is_lec_err(lec))
>                         work_done += m_can_handle_lec_err(dev, lec);
> 
>                 if (is_lec_err(dlec))
>                         work_done += m_can_handle_lec_err(dev, dlec);
> 
> > +			u8 dlec = FIELD_GET(PSR_DLEC_MASK, psr);
> > +
> > +			if (is_lec_err(dlec)) {
> > +				netdev_dbg(dev, "Data phase error
> detected\n");
> 
> If you add a debug, please add one for the Arbitration phase, too.
I have added the debug print specially for dlec (data phase). So we can differentiate lec errors (for all type of frames except FD with BRS) and Data phase errors, as we are calling same handler function for both the errors.

If I understood your comment correctly, you are asking something like below:
        /* handle protocol errors in arbitration phase */
        if ((cdev->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) &&
-           m_can_is_protocol_err(irqstatus))
+           m_can_is_protocol_err(irqstatus)) {
+               netdev_dbg(dev, "Arbitration phase error detected\n");
                work_done += m_can_handle_protocol_error(dev, irqstatus);
+       }

If the above implementation is correct as per your review comment, I think we don't need the above changes because 
Debug print for arbitration failure are already there in " m_can_handle_protocol_error" function.

> 
> > +				work_done += m_can_handle_lec_err(dev,
> dlec);
> > +			}
> > +		}
> >  	}
> >
> >  	/* handle protocol errors in arbitration phase */
> 
> regards,
> Marc
> 
> --
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