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From:   "Vivek Yadav" <vivek.2311@samsung.com>
To:     "'Marc Kleine-Budde'" <mkl@pengutronix.de>
Cc:     <rcsekar@samsung.com>, <wg@grandegger.com>, <davem@davemloft.net>,
        <edumazet@google.com>, <kuba@kernel.org>, <pabeni@redhat.com>,
        <pankaj.dubey@samsung.com>, <ravi.patel@samsung.com>,
        <linux-can@vger.kernel.org>, <netdev@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
In-Reply-To: <20221014071114.a6ls5ay56xk4cin3@pengutronix.de>
Subject: RE: [PATCH v2] can: mcan: Add support for handling DLEC error on
 CAN FD
Date:   Fri, 14 Oct 2022 16:53:19 +0530
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> -----Original Message-----
> From: Marc Kleine-Budde =5Bmailto:mkl=40pengutronix.de=5D
> Sent: 14 October 2022 12:41
> To: Vivek Yadav <vivek.2311=40samsung.com>
> Cc: rcsekar=40samsung.com; wg=40grandegger.com; davem=40davemloft.net;
> edumazet=40google.com; kuba=40kernel.org; pabeni=40redhat.com;
> pankaj.dubey=40samsung.com; ravi.patel=40samsung.com; linux-
> can=40vger.kernel.org; netdev=40vger.kernel.org; linux-
> kernel=40vger.kernel.org
> Subject: Re: =5BPATCH v2=5D can: mcan: Add support for handling DLEC erro=
r on
> CAN FD
>=20
> 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=40samsung.com>
> > ---
> > This patch is dependent on following patch from Marc:
> > =5B1=5D:
> > https://lore.kernel.org/all/20221012074205.691384-1-mkl=40pengutronix.d=
e
> > /
> >
> >  drivers/net/can/m_can/m_can.c =7C 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
> > =40=40 -156,6 +156,7 =40=40 enum m_can_reg =7B
> >  =23define PSR_EW		BIT(6)
> >  =23define PSR_EP		BIT(5)
> >  =23define PSR_LEC_MASK	GENMASK(2, 0)
> > +=23define PSR_DLEC_MASK   GENMASK(8, 10)
> >
> >  /* Interrupt Register (IR) */
> >  =23define IR_ALL_INT	0xffffffff
> > =40=40 -876,8 +877,16 =40=40 static int m_can_handle_bus_errors(struct
> net_device *dev, u32 irqstatus,
> >  	if (cdev->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) =7B
> >  		u8 lec =3D FIELD_GET(PSR_LEC_MASK, psr);
> >
> > -		if (is_lec_err(lec))
> > +		if (is_lec_err(lec)) =7B
> >  			work_done +=3D m_can_handle_lec_err(dev, lec);
> > +		=7D else =7B
>=20
> In case of high interrupt latency there might be lec and dlec errors pend=
ing.
> As this is error handling and not the hot path, please check for both, i.=
e.:
Okay will do that.
>=20
>                 if (is_lec_err(lec))
>                         work_done +=3D m_can_handle_lec_err(dev, lec);
>=20
>                 if (is_lec_err(dlec))
>                         work_done +=3D m_can_handle_lec_err(dev, dlec);
>=20
> > +			u8 dlec =3D FIELD_GET(PSR_DLEC_MASK, psr);
> > +
> > +			if (is_lec_err(dlec)) =7B
> > +				netdev_dbg(dev, =22Data phase error
> detected=5Cn=22);
>=20
> 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 dif=
ferentiate 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)) =7B
+               netdev_dbg(dev, =22Arbitration phase error detected=5Cn=22)=
;
                work_done +=3D m_can_handle_protocol_error(dev, irqstatus);
+       =7D

If the above implementation is correct as per your review comment, I think =
we don't need the above changes because=20
Debug print for arbitration failure are already there in =22 m_can_handle_p=
rotocol_error=22 function.

>=20
> > +				work_done +=3D m_can_handle_lec_err(dev,
> dlec);
> > +			=7D
> > +		=7D
> >  	=7D
> >
> >  	/* handle protocol errors in arbitration phase */
>=20
> regards,
> Marc
>=20
> --
> Pengutronix e.K.                 =7C Marc Kleine-Budde           =7C
> Embedded Linux                   =7C
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