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Message-ID: <20210530141502.561920a7@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
Date: Sun, 30 May 2021 14:15:02 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Steen Hegelund <steen.hegelund@...rochip.com>
Cc: "David S. Miller" <davem@...emloft.net>,
Andrew Lunn <andrew@...n.ch>,
Russell King <linux@...linux.org.uk>,
"Microchip Linux Driver Support" <UNGLinuxDriver@...rochip.com>,
Alexandre Belloni <alexandre.belloni@...tlin.com>,
Madalin Bucur <madalin.bucur@....nxp.com>,
Mark Einon <mark.einon@...il.com>,
Masahiro Yamada <masahiroy@...nel.org>,
Arnd Bergmann <arnd@...db.de>,
Philipp Zabel <p.zabel@...gutronix.de>,
"Simon Horman" <simon.horman@...ronome.com>,
<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
Lars Povlsen <lars.povlsen@...rochip.com>
Subject: Re: [PATCH net-next v2 03/10] net: sparx5: add hostmode with
phylink support
On Fri, 28 May 2021 14:34:12 +0200 Steen Hegelund wrote:
> This patch adds netdevs and phylink support for the ports in the switch.
> It also adds register based injection and extraction for these ports.
>
> Frame DMA support for injection and extraction will be added in a later
> series.
> +struct net_device *sparx5_create_netdev(struct sparx5 *sparx5, u32 portno)
> +{
> + struct sparx5_port *spx5_port;
> + struct net_device *ndev;
> + u64 val;
> +
> + ndev = devm_alloc_etherdev(sparx5->dev, sizeof(struct sparx5_port));
> + if (!ndev)
> + return ERR_PTR(-ENOMEM);
> +
> + SET_NETDEV_DEV(ndev, sparx5->dev);
> + spx5_port = netdev_priv(ndev);
> + spx5_port->ndev = ndev;
> + spx5_port->sparx5 = sparx5;
> + spx5_port->portno = portno;
> + sparx5_set_port_ifh(spx5_port->ifh, portno);
> +
> + ndev->netdev_ops = &sparx5_port_netdev_ops;
> + ndev->features |= NETIF_F_LLTX; /* software tx */
Is your transmission method really lockless? How does
simultaneous Tx from two CPUs work?
> + val = ether_addr_to_u64(sparx5->base_mac) + portno + 1;
> + u64_to_ether_addr(val, ndev->dev_addr);
> +
> + return ndev;
> +}
> +static void sparx5_xtr_grp(struct sparx5 *sparx5, u8 grp, bool byte_swap)
> +{
> + bool eof_flag = false, pruned_flag = false, abort_flag = false;
> + struct net_device *netdev;
> + struct sparx5_port *port;
> + struct frame_info fi;
> + int i, byte_cnt = 0;
> + struct sk_buff *skb;
> + u32 ifh[IFH_LEN];
> + u32 *rxbuf;
> +
> + /* Get IFH */
> + for (i = 0; i < IFH_LEN; i++)
> + ifh[i] = spx5_rd(sparx5, QS_XTR_RD(grp));
> +
> + /* Decode IFH (whats needed) */
> + sparx5_ifh_parse(ifh, &fi);
> +
> + /* Map to port netdev */
> + port = fi.src_port < SPX5_PORTS ?
> + sparx5->ports[fi.src_port] : NULL;
> + if (!port || !port->ndev) {
> + dev_err(sparx5->dev, "Data on inactive port %d\n", fi.src_port);
> + sparx5_xtr_flush(sparx5, grp);
> + return;
You should probably increment appropriate counter for each error
condition.
> + }
> +
> + /* Have netdev, get skb */
> + netdev = port->ndev;
> + skb = netdev_alloc_skb(netdev, netdev->mtu + ETH_HLEN);
> + if (!skb) {
> + sparx5_xtr_flush(sparx5, grp);
> + dev_err(sparx5->dev, "No skb allocated\n");
> + return;
> + }
> + rxbuf = (u32 *)skb->data;
> +
> + /* Now, pull frame data */
> + while (!eof_flag) {
> + u32 val = spx5_rd(sparx5, QS_XTR_RD(grp));
> + u32 cmp = val;
> +
> + if (byte_swap)
> + cmp = ntohl((__force __be32)val);
> +
> + switch (cmp) {
> + case XTR_NOT_READY:
> + break;
> + case XTR_ABORT:
> + /* No accompanying data */
> + abort_flag = true;
> + eof_flag = true;
> + break;
> + case XTR_EOF_0:
> + case XTR_EOF_1:
> + case XTR_EOF_2:
> + case XTR_EOF_3:
> + /* This assumes STATUS_WORD_POS == 1, Status
> + * just after last data
> + */
> + byte_cnt -= (4 - XTR_VALID_BYTES(val));
> + eof_flag = true;
> + break;
> + case XTR_PRUNED:
> + /* But get the last 4 bytes as well */
> + eof_flag = true;
> + pruned_flag = true;
> + fallthrough;
> + case XTR_ESCAPE:
> + *rxbuf = spx5_rd(sparx5, QS_XTR_RD(grp));
> + byte_cnt += 4;
> + rxbuf++;
> + break;
> + default:
> + *rxbuf = val;
> + byte_cnt += 4;
> + rxbuf++;
> + }
> + }
> +
> + if (abort_flag || pruned_flag || !eof_flag) {
> + netdev_err(netdev, "Discarded frame: abort:%d pruned:%d eof:%d\n",
> + abort_flag, pruned_flag, eof_flag);
> + kfree_skb(skb);
> + return;
> + }
> +
> +#if defined(CONFIG_DEBUG_KERNEL) /* TODO: Remove before upstreaming */
> + if (!netif_oper_up(netdev)) {
> + netdev_err(netdev, "Discarded frame: Interface not up\n");
> + kfree_skb(skb);
> + return;
> + }
> +#endif
> +
> + /* Finish up skb */
> + skb_put(skb, byte_cnt - ETH_FCS_LEN);
> + eth_skb_pad(skb);
> + skb->protocol = eth_type_trans(skb, netdev);
> + netif_rx(skb);
> + netdev->stats.rx_bytes += skb->len;
> + netdev->stats.rx_packets++;
Does the Rx really need to happen in an interrupt context?
Did you consider using NAPI or a tasklet?
> +}
> +
> +static int sparx5_inject(struct sparx5 *sparx5,
> + u32 *ifh,
> + struct sk_buff *skb)
> +{
> + int grp = INJ_QUEUE;
> + u32 val, w, count;
> + u8 *buf;
> +
> + val = spx5_rd(sparx5, QS_INJ_STATUS);
> + if (!(QS_INJ_STATUS_FIFO_RDY_GET(val) & BIT(grp))) {
> + pr_err("Injection: Queue not ready: 0x%lx\n",
> + QS_INJ_STATUS_FIFO_RDY_GET(val));
non-rate-limited errors on the datapath are a bad idea
> + return -EBUSY;
What do you expect to happen at this point? Kernel can retry sending
for ever, is there a way for the driver to find out that the fifo is
no longer busy to stop/start the software queuing appropriately?
> + }
> +
> + if (QS_INJ_STATUS_WMARK_REACHED_GET(val) & BIT(grp)) {
> + pr_err("Injection: Watermark reached: 0x%lx\n",
> + QS_INJ_STATUS_WMARK_REACHED_GET(val));
> + return -EBUSY;
ditto
> + }
> +
> + /* Indicate SOF */
> + spx5_wr(QS_INJ_CTRL_SOF_SET(1) |
> + QS_INJ_CTRL_GAP_SIZE_SET(1),
> + sparx5, QS_INJ_CTRL(grp));
> +
> + // Write the IFH to the chip.
Why the mix of comment styles?
> + for (w = 0; w < IFH_LEN; w++)
> + spx5_wr(ifh[w], sparx5, QS_INJ_WR(grp));
> +
> + /* Write words, round up */
> + count = ((skb->len + 3) / 4);
DIV_ROUND_UP()
> + buf = skb->data;
> + for (w = 0; w < count; w++, buf += 4) {
> + val = get_unaligned((const u32 *)buf);
> + spx5_wr(val, sparx5, QS_INJ_WR(grp));
> + }
> +
> + /* Add padding */
> + while (w < (60 / 4)) {
> + spx5_wr(0, sparx5, QS_INJ_WR(grp));
> + w++;
> + }
> +
> + /* Indicate EOF and valid bytes in last word */
> + spx5_wr(QS_INJ_CTRL_GAP_SIZE_SET(1) |
> + QS_INJ_CTRL_VLD_BYTES_SET(skb->len < 60 ? 0 : skb->len % 4) |
> + QS_INJ_CTRL_EOF_SET(1),
> + sparx5, QS_INJ_CTRL(grp));
> +
> + /* Add dummy CRC */
> + spx5_wr(0, sparx5, QS_INJ_WR(grp));
> + w++;
> +
> + return NETDEV_TX_OK;
> +}
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