netdev - Re: [PATCH 3/3] net: hisilicon: new hip04 ethernet driver

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Date:	Tue, 25 Mar 2014 09:12:38 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Zhangfei Gao <zhangfei.gao@...il.com>
Cc:	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	Mark Rutland <mark.rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	netdev <netdev@...r.kernel.org>,
	Zhangfei Gao <zhangfei.gao@...aro.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 3/3] net: hisilicon: new hip04 ethernet driver

On Tuesday 25 March 2014 12:06:31 Zhangfei Gao wrote:
> Dear Arnd
> 
> On Mon, Mar 24, 2014 at 11:18 PM, Arnd Bergmann <arnd@...db.de> wrote:
> > On Monday 24 March 2014 22:14:56 Zhangfei Gao wrote:
> >
> >> +
> >> +static void hip04_tx_reclaim(struct net_device *ndev, bool force)
> >> +{
> >> +     struct hip04_priv *priv = netdev_priv(ndev);
> >> +     unsigned tx_head = priv->tx_head;
> >> +     unsigned tx_tail = priv->tx_tail;
> >> +     struct tx_desc *desc = &priv->tx_desc[priv->tx_tail];
> >> +
> >> +     while (tx_tail != tx_head) {
> >> +             if (desc->send_addr != 0) {
> >> +                     if (force)
> >> +                             desc->send_addr = 0;
> >> +                     else
> >> +                             break;
> >> +             }
> >> +             if (priv->tx_phys[tx_tail]) {
> >> +                     dma_unmap_single(&ndev->dev, priv->tx_phys[tx_tail],
> >> +                             priv->tx_skb[tx_tail]->len, DMA_TO_DEVICE);
> >> +                     priv->tx_phys[tx_tail] = 0;
> >> +             }
> >> +             dev_kfree_skb_irq(priv->tx_skb[tx_tail]);
> >> +             priv->tx_skb[tx_tail] = NULL;
> >> +             tx_tail = TX_NEXT(tx_tail);
> >> +             priv->tx_count--;
> >> +     }
> >> +     priv->tx_tail = tx_tail;
> >> +}
> >
> > I think you still need to find a solution to ensure that the tx reclaim is
> > called eventually through a method other than start_xmit.
> 
> In the iperf stress test, if move reclaim to poll, there is some
> error, sometimes sending zero packets.
> While keep reclaim in the xmit to reclaim transmitted packets looks
> stable in the test,
> There TX_DESC_NUM desc can be used.

What I meant is that you need a correct implementation, presumably
you added a bug when you moved the function to poll(), and also you
forgot to add a timer.

> >> +     priv->map = syscon_regmap_lookup_by_compatible("hisilicon,hip04-ppe");
> >> +     if (IS_ERR(priv->map)) {
> >> +             dev_warn(d, "no hisilicon,hip04-ppe\n");
> >> +             ret = PTR_ERR(priv->map);
> >> +             goto init_fail;
> >> +     }
> >> +
> >> +     n = of_parse_phandle(node, "port-handle", 0);
> >> +     if (n) {
> >> +             ret = of_property_read_u32(n, "reg", &priv->port);
> >> +             if (ret) {
> >> +                     dev_warn(d, "no reg info\n");
> >> +                     goto init_fail;
> >> +             }
> >> +
> >> +             ret = of_property_read_u32(n, "channel", &priv->chan);
> >> +             if (ret) {
> >> +                     dev_warn(d, "no channel info\n");
> >> +                     goto init_fail;
> >> +             }
> >> +     } else {
> >> +             dev_warn(d, "no port-handle\n");
> >> +             ret = -EINVAL;
> >> +             goto init_fail;
> >> +     }
> >
> > Doing the lookup by "compatible" string doesn't really help you
> > at solve the problem of single-instance ppe at all, because that
> > function will only ever look at the first one. Use
> > syscon_regmap_lookup_by_phandle instead and pass the phandle
> > you get from the "port-handle" property.
> 
> Did some experiment, the only ppe base is got from syscon probe.
> And looking up by "compatible" did work for three controllers at the same time.

The point is that it won't work for more than one ppe instance.

> > Also, since you decided to treat the ppe as a dump regmap, I would
> > recommend moving the 'reg' and 'channel' properties into arguments
> > of the port-handle link, and retting rid of the child nodes of
> > the ppe, like:
> >
> > +       ppe: ppe@...0000 {
> > +               compatible = "hisilicon,hip04-ppe", "syscon";
> > +               reg = <0x28c0000 0x10000>;
> > +       };
> > +
> > +       fe: ethernet@...0000 {
> > +               compatible = "hisilicon,hip04-mac";
> > +               reg = <0x28b0000 0x10000>;
> > +               interrupts = <0 413 4>;
> > +               phy-mode = "mii";
> > +               port-handle = <&ppe 0xf1 0>;
> > +       };
> >
> 
> Would you mind giving more hints about how to parse the args.
> I am thinking of using of_parse_phandle_with_args, is that correct method?

I would just use of_property_read_u32_array() to read all three cells,
then pass the first cell entry into syscon_regmap_lookup_by_phandle.
of_parse_phandle_with_args() is what you would use if you were registering
a higher-level driver for the ppe rather than using syscon.

	Arnd
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