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Date:   Fri, 14 Oct 2022 09:11:14 +0200
From:   Marc Kleine-Budde <mkl@pengutronix.de>
To:     Vivek Yadav <vivek.2311@samsung.com>
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
Subject: Re: [PATCH v2] can: mcan: Add support for handling DLEC error on CAN
 FD
Message-ID: <20221014071114.a6ls5ay56xk4cin3@pengutronix.de>
References: <CGME20221014053017epcas5p359d337008999640fa140c691f47bc79c@epcas5p3.samsung.com>
 <20221014050332.45045-1-vivek.2311@samsung.com>
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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.
>=20
> 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.
>=20
> Signed-off-by: Vivek Yadav <vivek.2311@samsung.com>
> ---
> This patch is dependent on following patch from Marc:
> [1]: https://lore.kernel.org/all/20221012074205.691384-1-mkl@pengutronix.=
de/
>=20
>  drivers/net/can/m_can/m_can.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>=20
> 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)
> =20
>  /* 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 =3D FIELD_GET(PSR_LEC_MASK, psr);
> =20
> -		if (is_lec_err(lec))
> +		if (is_lec_err(lec)) {
>  			work_done +=3D 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.:

                if (is_lec_err(lec))
                        work_done +=3D m_can_handle_lec_err(dev, lec);

                if (is_lec_err(dlec))
                        work_done +=3D m_can_handle_lec_err(dev, dlec);

> +			u8 dlec =3D 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.

> +				work_done +=3D m_can_handle_lec_err(dev, dlec);
> +			}
> +		}
>  	}
> =20
>  	/* handle protocol errors in arbitration phase */

regards,
Marc

--=20
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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