netdev - Re: [PATCH net-next v6 4/6] net: mdio: Add RTL9300 MDIO driver

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Message-ID: <091a2e9cc6fedd99f35da124f67a54b69478648f.camel@svanheule.net>
Date: Sun, 09 Feb 2025 15:19:29 +0100
From: Sander Vanheule <sander@...nheule.net>
To: Chris Packham <chris.packham@...iedtelesis.co.nz>, lee@...nel.org, 
	robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
 andrew+netdev@...n.ch, 	davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, 	tsbogend@...ha.franken.de,
 hkallweit1@...il.com, linux@...linux.org.uk, 	daniel@...rotopia.org,
 markus.stockhausen@....de
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, linux-mips@...r.kernel.org
Subject: Re: [PATCH net-next v6 4/6] net: mdio: Add RTL9300 MDIO driver

Hi Chris,

On Tue, 2025-02-04 at 16:02 +1300, Chris Packham wrote:
> Add a driver for the MDIO controller on the RTL9300 family of Ethernet
> switches with integrated SoC. There are 4 physical SMI interfaces on the
> RTL9300 however access is done using the switch ports. The driver takes
> the MDIO bus hierarchy from the DTS and uses this to configure the
> switch ports so they are associated with the correct PHY. This mapping
> is also used when dealing with software requests from phylib.
> 
> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
> ---
> 
> Notes:
>     Changes in v6:
>     - Parse port->phy mapping from devicetree removing the need for the
>       realtek,port property

Good to see you found a way to do this!


> +/*
> + * MDIO controller for RTL9300 switches with integrated SoC.
> + *
> + * The MDIO communication is abstracted by the switch. At the software level
> + * communication uses the switch port to address the PHY. We work out the
> + * mapping based on the MDIO bus described in device tree and the realtek,port
> + * property.
> + */

Needs an update again ;-)


> +static int rtl9300_mdio_phy_to_port(struct mii_bus *bus, int phy_id)
> +{
> +	struct rtl9300_mdio_chan *chan = bus->priv;
> +	struct rtl9300_mdio_priv *priv = chan->priv;
> +	int i;
> +
> +	for (i = find_first_bit(priv->valid_ports, MAX_PORTS);
> +	     i < MAX_PORTS;
> +	     i = find_next_bit(priv->valid_ports, MAX_PORTS, i + 1))

You could use the for_each_set_bit(i, priv->valid_ports, MAX_PORTS) loop macro.


> +static int rtl9300_mdio_read_c22(struct mii_bus *bus, int phy_id, int regnum)
> +{
[...]
> +
> +	err = regmap_write(regmap, SMI_ACCESS_PHY_CTRL_2, port << 16);

Another candidate for FIELD_PREP()

> +	if (err)
> +		return err;
> +
> +	val = FIELD_PREP(GENMASK(24, 20), regnum) |
> +	      FIELD_PREP(GENMASK(19, 15), 0x1f) |
> +	      FIELD_PREP(GENMASK(14, 3), 0xfff) |

You could use #define-s for the GENMASK() field masks too, similar to PHY_CTRL_*. That
would make what you're setting a bit clearer, compared to these literal values.

Nit: You're also setting all-one values, so GENMASK(19, 15) and GENMASK(14, 3) by
themselves are sufficient. E.g. PHY_CTRL_NO_PAGE_PARK and PHY_CTRL_NO_PAGE_SELECT.



> +static int rtl9300_mdiobus_probe(struct platform_device *pdev)
> +{
[...]
> +
> +	device_for_each_child_node(dev, child) {
> +		err = rtl9300_mdiobus_probe_one(dev, priv, child);

In your next patch you use 'status = "disabled"' for the base dtsi. You may want to use
fwnode_for_each_available_child_node() in that case, so unused busses are not probed.


Best,
Sander