Messages in this thread | | | Date | Thu, 18 Aug 2022 15:08:14 +0200 | From | Marc Kleine-Budde <> | Subject | Re: [RFC PATCH 4/4] can: bxcan: add support for ST bxCAN controller |
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On 18.08.2022 12:30:31, Marc Kleine-Budde wrote: > One step at a time, let's look at the TX path: > > On 17.08.2022 16:35:29, Dario Binacchi wrote: > > +static netdev_tx_t bxcan_start_xmit(struct sk_buff *skb, > > + struct net_device *ndev) > > +{ > > + struct bxcan_priv *priv = netdev_priv(ndev); > > + struct can_frame *cf = (struct can_frame *)skb->data; > > + struct bxcan_regs *regs = priv->regs; > > + struct bxcan_mb *mb_regs; > > __iomem? > > > + unsigned int mb_id; > > + u32 id, tsr; > > + int i, j; > > + > > + if (can_dropped_invalid_skb(ndev, skb)) > > + return NETDEV_TX_OK; > > + > > + tsr = readl(®s->tsr); > > + mb_id = ffs((tsr & BXCAN_TSR_TME) >> BXCAN_TSR_TME_SHIFT); > > We want to send the CAN frames in the exact order they are pushed into > the driver, so don't pick the first free mailbox you find. How a are > priorities for the TX mailboxes handled? > > Is the mailbox with the lowest number send first? Is there a priority > field in the mailbox?
I just had a look into the data sheet and it says that the TX mailboxes are handled in transmit request order. This is good.
[...]
> The mcp251xfd has a proper hardware FIFO ring buffer for TX, the bxcan > probably doesn't. The get_tx_free() check is a bit different. Look at > c_can_get_tx_free() in:
This means you can use the simpler get_tx_free from the mcp251xfd driver. > > | https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=28e86e9ab522e65b08545e5008d0f1ac5b19dad1 > > This patch is a good example for the relevant changes.
This patch is non the less a good example for the TX path.
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 | [unhandled content-type:application/pgp-signature] | |