netdev - RE: [PATCH/RFC 2/2] ravb: Add GbEthernet driver support

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Date:   Thu, 15 Jul 2021 10:31:24 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>,
        Sergey Shtylyov <s.shtylyov@...russia.ru>,
        Adam Ford <aford173@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Andrew Gabbasov <andrew_gabbasov@...tor.com>,
        Yuusuke Ashizuka <ashiduka@...itsu.com>,
        netdev <netdev@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: RE: [PATCH/RFC 2/2] ravb: Add GbEthernet driver support

Hi Geert,

Thanks for the feedback.

> Subject: Re: [PATCH/RFC 2/2] ravb: Add GbEthernet driver support
> 
> Hi Biju,
> 
> On Wed, Jul 14, 2021 at 4:54 PM Biju Das <biju.das.jz@...renesas.com>
> wrote:
> > Add Gigabit Ethernet driver support.
> >
> > The Gigabit Etherner IP consists of Ethernet controller (E-MAC),
> > Internal TCP/IP Offload Engine (TOE) and Dedicated Direct memory
> > access controller (DMAC).
> >
> > Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> 
> Thanks for your patch!
> 
> > --- a/drivers/net/ethernet/renesas/ravb.h
> > +++ b/drivers/net/ethernet/renesas/ravb.h
> 
> > @@ -986,6 +1068,7 @@ struct ravb_ptp {  enum ravb_chip_id {
> >         RCAR_GEN2,
> >         RCAR_GEN3,
> > +       RZ_G2L,
> >  };
> 
> Instead of adding another chip type, it may be better to replace the chip
> type by a structure with feature bits, values, and function pointers (see
> examples below).
 
> BTW given the ravb driver is based on the sh_eth driver ("Ethernet AVB
> includes an Gigabit Ethernet controller (E-MAC) that is basically
> compatible with SuperH Gigabit Ethernet E-MAC"), and seeing the amount of
> changes, I'm wondering if rgeth is closer to sh_eth? ;-)

With sh_eth driver,We can reuse only E-MAC IP. But with RAVB we can reuse both DMAC and E-MAC.
Hence I believe it is closer to AVB.

> 
> > --- a/drivers/net/ethernet/renesas/ravb_main.c
> > +++ b/drivers/net/ethernet/renesas/ravb_main.c
> 
> > @@ -247,8 +288,12 @@ static void ravb_ring_free(struct net_device *ndev,
> int q)
> >         int ring_size;
> >         int i;
> >
> > -       if (priv->rx_ring[q]) {
> > -               ravb_ring_free_ex(ndev, q);
> > +       if (priv->chip_id == RZ_G2L) {
> > +               if (priv->rgeth_rx_ring[q])
> > +                       rgeth_ring_free_ex(ndev, q);
> > +       } else {
> > +               if (priv->rx_ring[q])
> > +                       ravb_ring_free_ex(ndev, q);
> >         }
> 
> Could be called through a function pointer instead.

OK.
> 
> > @@ -356,7 +434,7 @@ static void ravb_ring_format(struct net_device
> > *ndev, int q)  static int ravb_ring_init(struct net_device *ndev, int
> > q)  {
> >         struct ravb_private *priv = netdev_priv(ndev);
> > -       size_t skb_sz = RX_BUF_SZ;
> > +       size_t skb_sz = (priv->chip_id == RZ_G2L) ? RGETH_RCV_BUFF_MAX
> > + : RX_BUF_SZ;
> 
> Could use a value in the structure.
OK.
> 
> > @@ -730,7 +1054,7 @@ static void ravb_emac_interrupt_unlocked(struct
> net_device *ndev)
> >         ecsr = ravb_read(ndev, ECSR);
> >         ravb_write(ndev, ecsr, ECSR);   /* clear interrupt */
> >
> > -       if (ecsr & ECSR_MPD)
> > +       if (priv->chip_id != RZ_G2L && (ecsr & ECSR_MPD))
> 
> Could use a feature bit.

OK.

> 
> > @@ -2104,11 +2578,19 @@ static int ravb_probe(struct platform_device
> *pdev)
> >         priv = netdev_priv(ndev);
> >         priv->chip_id = chip_id;
> >
> > -       ndev->features = NETIF_F_RXCSUM;
> > -       ndev->hw_features = NETIF_F_RXCSUM;
> > -
> > -       pm_runtime_enable(&pdev->dev);
> > -       pm_runtime_get_sync(&pdev->dev);
> > +       if (chip_id == RZ_G2L) {
> > +               ndev->hw_features |= (NETIF_F_HW_CSUM | NETIF_F_RXCSUM);
> > +               priv->rstc = devm_reset_control_get(&pdev->dev, NULL);
> 
> R-Car Gen2 and Gen3 describe a reset in DT, too.
> Does it hurt to always use the reset?

OK will use reset.


> 
> > +               if (IS_ERR(priv->rstc)) {
> > +                       dev_err(&pdev->dev, "failed to get cpg
> > + reset\n");
> 
> dev_err_probe(), to avoid printing an error on -EPROBE_DEFER.

OK.


Regards,
Biju

> 
> > +                       free_netdev(ndev);
> > +                       return PTR_ERR(priv->rstc);
> > +               }
> > +               reset_control_deassert(priv->rstc);
> > +       } else {
> > +               ndev->features = NETIF_F_RXCSUM;
> > +               ndev->hw_features = NETIF_F_RXCSUM;
> > +       }
> 
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-
> m68k.org
> 
> In personal conversations with technical people, I call myself a hacker.
> But when I'm talking to journalists I just say "programmer" or something
> like that.
>                                 -- Linus Torvalds