Re: [PATCH net-next 04/12] net: pcs: add Renesas MII converter driver

Clément Léger
2022-04-14T15:48:15Z

Le Thu, 14 Apr 2022 13:49:08 +0100,
"Russell King (Oracle)" <linux@armlinux.org.uk> a écrit :

> On Thu, Apr 14, 2022 at 02:22:42PM +0200, Clément Léger wrote:
> > Add PCS driver for the MII converter that is present on Renesas RZ/N1
> > SoC. This MII converter is reponsible of converting MII to RMII/RGMII
> > or act as a MII passtrough. Exposing it as a PCS allows to reuse it
> > in both the switch driver and the stmmac driver. Currently, this driver
> > only allows the PCS to be used by the dual Cortex-A7 subsystem since
> > the register locking system is not used.
>
> Hi,
>
> > +#define MIIC_CONVCTRL_CONV_MODE GENMASK(4, 0)
> > +#define CONV_MODE_MII 0
> > +#define CONV_MODE_RMII BIT(2)
> > +#define CONV_MODE_RGMII BIT(3)
> > +#define CONV_MODE_10MBPS 0
> > +#define CONV_MODE_100MBPS BIT(0)
> > +#define CONV_MODE_1000MBPS BIT(1)
>
> Is this really a single 4-bit wide field? It looks like two 2-bit fields
> to me.

You are right, the datasheet presents that as a single bitfield but
that can be split.

>
> > +#define phylink_pcs_to_miic_port(pcs) container_of((pcs), struct miic_port, pcs)
>
> I prefer a helper function to a preprocessor macro for that, but I'm not
> going to insist on that point.

Acked.

>
> > +static void miic_link_up(struct phylink_pcs *pcs, unsigned int mode,
> > + phy_interface_t interface, int speed, int duplex)
> > +{
> > + struct miic_port *miic_port = phylink_pcs_to_miic_port(pcs);
> > + struct miic *miic = miic_port->miic;
> > + int port = miic_port->port;
> > + u32 val = 0;
> > +
> > + if (duplex == DUPLEX_FULL)
> > + val |= MIIC_CONVCTRL_FULLD;
> > +
> > + switch (interface) {
> > + case PHY_INTERFACE_MODE_RMII:
> > + val |= CONV_MODE_RMII;
> > + break;
> > + case PHY_INTERFACE_MODE_RGMII:
> > + val |= CONV_MODE_RGMII;
> > + break;
> > + case PHY_INTERFACE_MODE_MII:
> > + val |= CONV_MODE_MII;
> > + break;
> > + default:
> > + dev_err(miic->dev, "Unsupported interface %s\n",
> > + phy_modes(interface));
> > + return;
> > + }
>
> Why are you re-decoding the interface mode? The interface mode won't
> change as a result of a call to link-up. Changing the interface mode
> is a major configuration event that will always see a call to your
> miic_config() function first.

Indeed, seems stupid, I will simply keep the mode bits once split from
speed.

[...]

> > +};
> > +
> > +struct phylink_pcs *miic_create(struct device_node *np)
> > +{
> > + struct platform_device *pdev;
> > + struct miic_port *miic_port;
> > + struct device_node *pcs_np;
> > + u32 port;
> > +
> > + if (of_property_read_u32(np, "reg", &port))
> > + return ERR_PTR(-EINVAL);
> > +
> > + if (port >= MIIC_MAX_NR_PORTS)
> > + return ERR_PTR(-EINVAL);
> > +
> > + /* The PCS pdev is attached to the parent node */
> > + pcs_np = of_get_parent(np);
> > + if (!pcs_np)
> > + return ERR_PTR(-EINVAL);
> > +
> > + pdev = of_find_device_by_node(pcs_np);
> > + if (!pdev || !platform_get_drvdata(pdev))
> > + return ERR_PTR(-EPROBE_DEFER);
>
> It would be a good idea to have a comment in the probe function to say
> that this relies on platform_set_drvdata() being the very last thing
> after a point where initialisation is complete and we won't fail.

Yep, sounds like a good idea.

>
> Thanks!
>

Thanks for the review,

--
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin