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Date:   Tue, 22 Dec 2020 10:46:12 +0100
From:   Steen Hegelund <steen.hegelund@...rochip.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Mark Einon <mark.einon@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        "Arnd Bergmann" <arnd@...db.de>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH v2 3/8] net: sparx5: add hostmode with phylink
 support

Hi Andrew,

On Sat, 2020-12-19 at 20:51 +0100, Andrew Lunn wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
> 
> > +     /* Create a phylink for PHY management.  Also handles SFPs */
> > +     spx5_port->phylink_config.dev = &spx5_port->ndev->dev;
> > +     spx5_port->phylink_co
> > nfig.type = PHYLINK_NETDEV;
> > +     spx5_port->phylink_config.pcs_poll = true;
> > +
> > +     /* phylink needs a valid interface mode to parse dt node */
> > +     if (phy_mode == PHY_INTERFACE_MODE_NA)
> > +             phy_mode = PHY_INTERFACE_MODE_10GBASER;
> 
> Maybe just enforce a valid value in DT?

Maybe I need to clarify that you must choose between an Ethernet cuPHY
or an SFP, so it is optional.
> 
> > +/* Configuration */
> > +static inline bool sparx5_use_cu_phy(struct sparx5_port *port)
> > +{
> > +     return port->conf.phy_mode != PHY_INTERFACE_MODE_NA;
> > +}
> 
> That is a rather odd definition of copper.

Should I rather use a bool property to select between the two options
(cuPHY or SFP)?

> 
> > diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_netdev.c
> > b/drivers/net/ethernet/microchip/sparx5/sparx5_netdev.c
> > new file mode 100644
> > index 000000000000..6f9282e9d3f4
> > --- /dev/null
> > +++ b/drivers/net/ethernet/microchip/sparx5/sparx5_netdev.c
> > @@ -0,0 +1,203 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/* Microchip Sparx5 Switch driver
> > + *
> > + * Copyright (c) 2020 Microchip Technology Inc. and its
> > subsidiaries.
> > + */
> > +
> > +#include "sparx5_main.h"
> 
> I don't actually know what is preferred here, but very few drivers
> i've reviewed put all the required headers into another header
> file. They normally list them in each .c file.

I will look at reworking this. 

> 
> > +static int sparx5_port_open(struct net_device *ndev)
> > +{
> > +     struct sparx5_port *port = netdev_priv(ndev);
> > +     int err = 0;
> > +
> > +     err = phylink_of_phy_connect(port->phylink, port->of_node,
> > 0);
> > +     if (err) {
> > +             netdev_err(ndev, "Could not attach to PHY\n");
> > +             return err;
> > +     }
> > +
> > +     phylink_start(port->phylink);
> > +
> > +     if (!ndev->phydev) {
> 
> Humm. When is ndev->phydev set? I don't think phylink ever sets it.

Indirectly: phylink_of_phy_connect uses phy_attach_direct and that sets
the phydev.

> 
> > +             /* power up serdes */
> > +             port->conf.power_down = false;
> > +             err = phy_power_on(port->serdes);
> > +             if (err)
> > +                     netdev_err(ndev, "%s failed\n", __func__);
> > +     }
> > +
> > +     return err;
> > +}
> 
> > +struct net_device *sparx5_create_netdev(struct sparx5 *sparx5, u32
> > portno)
> > +{
> > +     struct net_device *ndev;
> > +     struct sparx5_port *spx5_port;
> > +
> > +     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);
> > +     snprintf(ndev->name, IFNAMSIZ, "eth%d", portno);
> > +
> > +     ether_setup(ndev);
> 
> devm_alloc_etherdev() should of already called ether_setup().

Ah - yes it is the setup(dev) call in alloc_netdev_mqs. I will remove
that then.
> 
> > +     ndev->netdev_ops = &sparx5_port_netdev_ops;
> > +     ndev->features |= NETIF_F_LLTX; /* software tx */
> > +
> > +     ether_addr_copy(ndev->dev_addr, sparx5->base_mac);
> > +     ndev->dev_addr[ETH_ALEN - 1] += portno + 1;
> 
> That will cause some surprises with wrap around. Use eth_addr_inc()

OK - will do.

> 
> > +static void sparx5_xtr_grp(struct sparx5 *sparx5, u8 grp, bool
> > byte_swap)
> > +{
> > +     int i, byte_cnt = 0;
> > +     bool eof_flag = false, pruned_flag = false, abort_flag =
> > false;
> > +     u32 ifh[IFH_LEN];
> > +     struct sk_buff *skb;
> > +     struct frame_info fi;
> > +     struct sparx5_port *port;
> > +     struct net_device *netdev;
> > +     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;
> > +     }
> > +
> > +     /* 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 (!netif_oper_up(netdev)) {
> > +             netdev_err(netdev, "Discarded frame: Interface not
> > up\n");
> > +             kfree_skb(skb);
> > +             return;
> > +     }
> 
> Why is it sending frames when it is not up?

This is intended for received frames. A situation where the lower
layers have been enabled correctly but not the port.

> 
> > +static int sparx5_inject(struct sparx5 *sparx5,
> > +                      u32 *ifh,
> > +                      struct sk_buff *skb)
> > +{
> > +     u32 val, w, count;
> > +     int grp = INJ_QUEUE;
> > +     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));
> > +             return -1;
> 
> Always use -ESOMETHING.

Yes.

> 
> > +     }
> > +
> > +     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 -1;
> > +     }
> > +
> > +     /* 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.
> > +     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);
> > +     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));
> > +     }
> 
> No DMA? What sort of performance do you get? Enough for the odd BPDU,
> IGMP frame etc, but i guess you don't want any real bulk data to be
> sent this way?

Yes the register based injection/extration is not going to be fast, but
the FDMA and its driver is being sent later as separate series to keep
the size of this review down.

> 
> > +irqreturn_t sparx5_xtr_handler(int irq, void *_sparx5)
> > +{
> > +     struct sparx5 *sparx5 = _sparx5;
> > +
> > +     /* Check data in queue */
> > +     while (spx5_rd(sparx5, QS_XTR_DATA_PRESENT) & BIT(XTR_QUEUE))
> > +             sparx5_xtr_grp(sparx5, XTR_QUEUE, false);
> > +
> > +     return IRQ_HANDLED;
> > +}
> 
> Is there any sort of limit how many times this will loop? If somebody
> is blasting 10Gbps at the CPU, will it ever get out of this loop?

Hmmm, not at the moment but this is because the FDMA driver is intended
to be used in these scenarios.

> 
>    Andrew

Thanks for your comments

BR
Steen

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