linux-kernel - Re: [PATCH RESEND 1/1] can: esd_usb: Allow REC and TEC to return to zero

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Date:   Fri, 25 Nov 2022 16:56:51 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Frank Jungclaus <frank.jungclaus@....eu>
Cc:     linux-can@...r.kernel.org, Wolfgang Grandegger <wg@...ndegger.com>,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        Stefan Mätje <stefan.maetje@....eu>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 1/1] can: esd_usb: Allow REC and TEC to return to
 zero

On 24.11.2022 21:38:06, Frank Jungclaus wrote:
> We don't get any further EVENT from an esd CAN USB device for changes
> on REC or TEC while those counters converge to 0 (with ecc == 0).
> So when handling the "Back to Error Active"-event force
> txerr = rxerr = 0, otherwise the berr-counters might stay on
> values like 95 forever ...
> 
> Also, to make life easier during the ongoing development a
> netdev_dbg() has been introduced to allow dumping error events send by
> an esd CAN USB device.
> 
> Signed-off-by: Frank Jungclaus <frank.jungclaus@....eu>

Please add a Fixes tag.

https://elixir.bootlin.com/linux/v6.0/source/Documentation/process/handling-regressions.rst#L107

> ---
>  drivers/net/can/usb/esd_usb.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/can/usb/esd_usb.c b/drivers/net/can/usb/esd_usb.c
> index 1bcfad11b1e4..da24c649aadd 100644
> --- a/drivers/net/can/usb/esd_usb.c
> +++ b/drivers/net/can/usb/esd_usb.c
> @@ -230,10 +230,14 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
>  
>  	if (id == ESD_EV_CAN_ERROR_EXT) {
>  		u8 state = msg->msg.rx.data[0];
> -		u8 ecc = msg->msg.rx.data[1];
> +		u8 ecc   = msg->msg.rx.data[1];

unrelated, please remove.

>  		u8 rxerr = msg->msg.rx.data[2];
>  		u8 txerr = msg->msg.rx.data[3];
>  
> +		netdev_dbg(priv->netdev,
> +			   "CAN_ERR_EV_EXT: dlc=%#02x state=%02x ecc=%02x rec=%02x tec=%02x\n",
> +			   msg->msg.rx.dlc, state, ecc, rxerr, txerr);
> +
>  		skb = alloc_can_err_skb(priv->netdev, &cf);
>  		if (skb == NULL) {
>  			stats->rx_dropped++;
> @@ -260,6 +264,8 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
>  				break;
>  			default:
>  				priv->can.state = CAN_STATE_ERROR_ACTIVE;
> +				txerr = 0;
> +				rxerr = 0;
>  				break;
>  			}
>  		} else {

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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