linux-kernel - Re: [RFC PATCH v2 4/4] can: bxcan: add support for ST bxCAN controller

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Date:   Sat, 27 Aug 2022 06:56:42 +0900
From:   Vincent Mailhol <vincent.mailhol@...il.com>
To:     Dario Binacchi <dario.binacchi@...rulasolutions.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Amarula patchwork <linux-amarula@...rulasolutions.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        michael@...rulasolutions.com, Dario Binacchi <dariobin@...ero.it>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH v2 4/4] can: bxcan: add support for ST bxCAN controller

On Sat. 20 Aug. 2022 à 17:32, Dario Binacchi
<dario.binacchi@...rulasolutions.com> a écrit :
> Add support for the basic extended CAN controller (bxCAN) found in many
> low- to middle-end STM32 SoCs. It supports the Basic Extended CAN
> protocol versions 2.0A and B with a maximum bit rate of 1 Mbit/s.
>
> The controller supports two channels (CAN1 as master and CAN2 as slave)
> and the driver can enable either or both of the channels. They share
> some of the required logic (e. g. clocks and filters), and that means
> you cannot use the slave CAN without enabling some hardware resources
> managed by the master CAN.
>
> Each channel has 3 transmit mailboxes, 2 receive FIFOs with 3 stages and
> 28 scalable filter banks.
> It also manages 4 dedicated interrupt vectors:
> - transmit interrupt
> - FIFO 0 receive interrupt
> - FIFO 1 receive interrupt
> - status change error interrupt
>
> Driver uses all 3 available mailboxes for transmission and FIFO 0 for
> reception. Rx filter rules are configured to the minimum. They accept
> all messages and assign filter 0 to CAN1 and filter 14 to CAN2 in
> identifier mask mode with 32 bits width. It enables and uses transmit,
> receive buffers for FIFO 0 and error and status change interrupts.
>
> Signed-off-by: Dario Binacchi <dariobin@...ero.it>
> Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
>
> ---

(...)

> +static void bxcan_handle_state_change(struct net_device *ndev, u32 esr)
> +{
> +       struct bxcan_priv *priv = netdev_priv(ndev);
> +       struct net_device_stats *stats = &ndev->stats;
> +       enum can_state new_state = priv->can.state;
> +       struct can_berr_counter bec;
> +       enum can_state rx_state, tx_state;
> +       struct sk_buff *skb;
> +       struct can_frame *cf;
> +
> +       /* Early exit if no error flag is set */
> +       if (!(esr & (BXCAN_ESR_EWGF | BXCAN_ESR_EPVF | BXCAN_ESR_BOFF)))
> +               return;
> +
> +       bec.txerr = BXCAN_TEC(esr);
> +       bec.rxerr = BXCAN_REC(esr);
> +
> +       if (esr & BXCAN_ESR_BOFF)
> +               new_state = CAN_STATE_BUS_OFF;
> +       else if (esr & BXCAN_ESR_EPVF)
> +               new_state = CAN_STATE_ERROR_PASSIVE;
> +       else if (esr & BXCAN_ESR_EWGF)
> +               new_state = CAN_STATE_ERROR_WARNING;
> +
> +       /* state hasn't changed */
> +       if (unlikely(new_state == priv->can.state))
> +               return;
> +
> +       skb = alloc_can_err_skb(ndev, &cf);
> +       if (unlikely(!skb))
> +               return;
> +
> +       tx_state = bec.txerr >= bec.rxerr ? new_state : 0;
> +       rx_state = bec.txerr <= bec.rxerr ? new_state : 0;
> +       can_change_state(ndev, cf, tx_state, rx_state);
> +
> +       if (new_state == CAN_STATE_BUS_OFF)
> +               can_bus_off(ndev);
> +
> +       stats->rx_bytes += cf->len;

Please do not increment the stats if the frame is remote (c.f. CAN_RTR_FLAG).

> +       stats->rx_packets++;
> +       netif_rx(skb);
> +}


Yours sincerely,
Vincent Mailhol