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From: Joel Stanley <joel@jms.id.au>
To: Jakub Kicinski <kuba@kernel.org>
Cc: "David S . Miller" <davem@davemloft.net>,
	Rob Herring <robh+dt@kernel.org>,
	Stafford Horne <shorne@gmail.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Anton Blanchard <anton@ozlabs.org>,
	Gabriel Somlo <gsomlo@gmail.com>, David Shah <dave@ds0.me>,
	Karol Gugala <kgugala@antmicro.com>,
	Mateusz Holenko <mholenko@antmicro.com>,
	devicetree <devicetree@vger.kernel.org>,
	Networking <netdev@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] net: Add driver for LiteX's LiteETH network interface
Date: Mon, 9 Aug 2021 12:03:36 +0000	[thread overview]
Message-ID: <CACPK8XcCjNWm=85uXX2tubP=WAgfF8ewqMAMWO_wJVeHB-U_0w@mail.gmail.com> (raw)
In-Reply-To: <20210806161030.52a7ae93@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>

Thanks for the review Jakub.

On Fri, 6 Aug 2021 at 23:10, Jakub Kicinski <kuba@kernel.org> wrote:
> > +static int liteeth_start_xmit(struct sk_buff *skb, struct net_device *netdev)
> > +{
> > +     struct liteeth *priv = netdev_priv(netdev);
> > +     void __iomem *txbuffer;
> > +     int ret;
> > +     u8 val;
> > +
> > +     /* Reject oversize packets */
> > +     if (unlikely(skb->len > MAX_PKT_SIZE)) {
> > +             if (net_ratelimit())
> > +                     netdev_dbg(netdev, "tx packet too big\n");
> > +             goto drop;
> > +     }
> > +
> > +     txbuffer = priv->tx_base + priv->tx_slot * LITEETH_BUFFER_SIZE;
> > +     memcpy_toio(txbuffer, skb->data, skb->len);
> > +     writeb(priv->tx_slot, priv->base + LITEETH_READER_SLOT);
> > +     writew(skb->len, priv->base + LITEETH_READER_LENGTH);
> > +
> > +     ret = readl_poll_timeout_atomic(priv->base + LITEETH_READER_READY, val, val, 5, 1000);
>
> Why the need for poll if there is an interrupt?
> Why not stop the Tx queue once you're out of slots and restart
> it when the completion interrupt comes?

That makes sense.

In testing I have not been able to hit the LITEETH_READER_READY
not-ready state. I assume it's there to say that the slots are full.

>
> > +     if (ret == -ETIMEDOUT) {
> > +             netdev_err(netdev, "LITEETH_READER_READY timed out\n");
>
> ratelimit this as well, please
>
> > +             goto drop;
> > +     }
> > +
> > +     writeb(1, priv->base + LITEETH_READER_START);
> > +
> > +     netdev->stats.tx_bytes += skb->len;
>
> Please count bytes and packets in the same place

AFAIK we don't know the length when the interrupt comes in, so we need
to count both here in xmit?

>
> > +     priv->tx_slot = (priv->tx_slot + 1) % priv->num_tx_slots;
> > +     dev_kfree_skb_any(skb);
> > +     return NETDEV_TX_OK;
> > +drop:
> > +     /* Drop the packet */
> > +     dev_kfree_skb_any(skb);
> > +     netdev->stats.tx_dropped++;
> > +
> > +     return NETDEV_TX_OK;
> > +}

  reply	other threads:[~2021-08-09 12:05 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-06  5:49 [PATCH 0/2] net: Add LiteETH network driver Joel Stanley
2021-08-06  5:49 ` [PATCH 1/2] dt-bindings: net: Add bindings for LiteETH Joel Stanley
2021-08-06 17:07   ` Rob Herring
2021-08-07 19:05   ` Andrew Lunn
2021-08-09  7:59     ` Joel Stanley
2021-08-09 13:27       ` Andrew Lunn
2021-08-06  5:49 ` [PATCH 2/2] net: Add driver for LiteX's LiteETH network interface Joel Stanley
2021-08-06 11:48   ` Gabriel L. Somlo
     [not found]     ` <CA+96J6JxAkNd_QkVxfSdAJwWVLJTtSaDsCmVKw3KBfYySJytKA@mail.gmail.com>
2021-08-20  7:46       ` Joel Stanley
2021-08-06 23:10   ` Jakub Kicinski
2021-08-09 12:03     ` Joel Stanley [this message]
2021-08-09 16:16       ` Jakub Kicinski
2021-08-07 19:19   ` Andrew Lunn
2021-08-09  3:20     ` Joel Stanley
2021-08-09 13:09       ` Andrew Lunn

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