netdev - Re: [PATCH] can: at91_can: fix passive-state AERR flooding

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Message-ID: <20211017124613.ttplab5ydklehvxd@pengutronix.de>
Date:   Sun, 17 Oct 2021 14:46:13 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Brandon Maier <brandon.maier@...kwellcollins.com>
Cc:     Wolfgang Grandegger <wg@...ndegger.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        "open list:CAN NETWORK DRIVERS" <linux-can@...r.kernel.org>,
        "open list:NETWORKING DRIVERS" <netdev@...r.kernel.org>,
        "moderated list:ARM/Microchip (AT91) SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] can: at91_can: fix passive-state AERR flooding

On 05.10.2021 13:30:23, Brandon Maier wrote:
> When the at91_can is a single node on the bus and a user attempts to
> transmit, the can state machine will report ack errors and increment the
> transmit error count until it reaches the passive-state. Per the
> specification, it will then transmit with a passive error, but will stop
> incrementing the transmit error count. This results in the host machine
> being flooded with the AERR interrupt forever, or until another node
> rejoins the bus.
> 
> To prevent the AERR flooding, disable the AERR interrupt when we are in
> passive mode.

Can you implement Bus Error Reporting?

| https://elixir.bootlin.com/linux/v5.14/source/include/uapi/linux/can/netlink.h#L99

This way the user can control if bus errors, and the ACK error is one of
them, should be reported. Bus error reporting is disabled by default. I
think enabling AT91_IRQ_ERR_FRAME only if CAN_CTRLMODE_BERR_REPORTING is
active should do the trick.

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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