netdev - Re: [PATCH 2/2] net: Add driver for LiteX's LiteETH network interface

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Message-ID: <YREo/wS8iagiuYBA@lunn.ch>
Date:   Mon, 9 Aug 2021 15:09:19 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Joel Stanley <joel@....id.au>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Stafford Horne <shorne@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Anton Blanchard <anton@...abs.org>,
        Gabriel Somlo <gsomlo@...il.com>, David Shah <dave@....me>,
        Karol Gugala <kgugala@...micro.com>,
        Mateusz Holenko <mholenko@...micro.com>,
        devicetree <devicetree@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] net: Add driver for LiteX's LiteETH network interface

On Mon, Aug 09, 2021 at 03:20:57AM +0000, Joel Stanley wrote:
> On Sat, 7 Aug 2021 at 19:19, Andrew Lunn <andrew@...n.ch> wrote:
> >
> > > +static void liteeth_reset_hw(struct liteeth *priv)
> > > +{
> > > +     /* Reset, twice */
> > > +     writeb(0, priv->base + LITEETH_PHY_CRG_RESET);
> > > +     udelay(10);
> > > +     writeb(1, priv->base + LITEETH_PHY_CRG_RESET);
> > > +     udelay(10);
> > > +     writeb(0, priv->base + LITEETH_PHY_CRG_RESET);
> > > +     udelay(10);
> >
> > What is this actually resetting?
> 
> This comes from the reference firmware that many (but not all) litex
> systems run before loading their operating system.
> 
> I'm not completely sure how necessary it still is; I will drop it for now.

Which did not answer my question. Once we know what is being reset, we
can maybe suggest when/how it should be reset.

> > > +static int liteeth_probe(struct platform_device *pdev)
> > > +{
> > > +     struct net_device *netdev;
> > > +     void __iomem *buf_base;
> > > +     struct resource *res;
> > > +     struct liteeth *priv;
> > > +     int irq, err;
> > > +
> > > +     netdev = alloc_etherdev(sizeof(*priv));
> > > +     if (!netdev)
> > > +             return -ENOMEM;
> > > +
> > > +     priv = netdev_priv(netdev);
> > > +     priv->netdev = netdev;
> > > +     priv->dev = &pdev->dev;
> > > +
> > > +     irq = platform_get_irq(pdev, 0);
> > > +     if (irq < 0) {
> > > +             dev_err(&pdev->dev, "Failed to get IRQ\n");
> > > +             goto err;
> > > +     }
> > > +
> > > +     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > +     priv->base = devm_ioremap_resource(&pdev->dev, res);
> > > +     if (IS_ERR(priv->base)) {
> > > +             err = PTR_ERR(priv->base);
> > > +             goto err;
> > > +     }
> > > +
> > > +     res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> > > +     priv->mdio_base = devm_ioremap_resource(&pdev->dev, res);
> > > +     if (IS_ERR(priv->mdio_base)) {
> > > +             err = PTR_ERR(priv->mdio_base);
> > > +             goto err;
> > > +     }
> >
> > So you don't have any PHY handling, or any MDIO bus master code. So i
> > would drop this, until the MDIO architecture question is answered. I
> > also wonder how much use the MAC driver is without any PHY code?
> > Unless you have a good reason, i don't think we should merge this
> > until it makes the needed calls into phylib. It is not much code to
> > add.
> 
> You mean I should skip out the parsing of the mdio base until I'm
> using it? That's reasonable.

It could be we insist you add MDIO and PHY handling. But first we need
to understand the architecture.

   Andrew