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

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Date:   Fri, 14 Oct 2022 09:11:14 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Vivek Yadav <vivek.2311@...sung.com>
Cc:     rcsekar@...sung.com, wg@...ndegger.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        pankaj.dubey@...sung.com, ravi.patel@...sung.com,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
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@...sung.com>
> ---
> This patch is dependent on following patch from Marc:
> [1]: https://lore.kernel.org/all/20221012074205.691384-1-mkl@pengutronix.de/
> 
>  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.:

                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.

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

regards,
Marc

-- 
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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