Re: [PATCH net-next 04/15] net: mdio: add generic driver for NXP SJA1110 100BASE-TX embedded PHYs

Maxime Chevallier
2025-11-20T17:56:02Z

Hi Vladimir,

On 18/11/2025 20:05, Vladimir Oltean wrote:
> This is the standalone variant of drivers/net/dsa/sja1105/sja1105_mdio.c.
> Same kind of differences between this driver and the embedded DSA one
> apply: regmap is being used for register access, and addresses are
> multiplied by 4 with regmap.
>
> In fact this is so generic that there is nothing NXP SJA1110 specific
> about it at all, and just instantiates mdio-regmap. I decided to name it
> mdio-regmap-simple.c in the style of drivers/mfd/simple-mfd-i2c.c which
> has support for various vendor compatible strings.
>
> Cc: Maxime Chevallier <maxime.chevallier@bootlin.com>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---
> MAINTAINERS | 1 +
> drivers/net/mdio/Kconfig | 14 +++--
> drivers/net/mdio/Makefile | 1 +
> drivers/net/mdio/mdio-regmap-simple.c | 77 +++++++++++++++++++++++++++
> 4 files changed, 90 insertions(+), 3 deletions(-)
> create mode 100644 drivers/net/mdio/mdio-regmap-simple.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c41b9d86c144..81c3dba6acd0 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -15473,6 +15473,7 @@ M: Maxime Chevallier <maxime.chevallier@bootlin.com>
> L: netdev@vger.kernel.org
> S: Maintained
> F: drivers/net/mdio/mdio-regmap.c
> +F: drivers/net/mdio/mdio-regmap-simple.c
> F: include/linux/mdio/mdio-regmap.h
>
> MEASUREMENT COMPUTING CIO-DAC IIO DRIVER
> diff --git a/drivers/net/mdio/Kconfig b/drivers/net/mdio/Kconfig
> index 9819d1dc18de..2f86a438a2a7 100644
> --- a/drivers/net/mdio/Kconfig
> +++ b/drivers/net/mdio/Kconfig
> @@ -179,14 +179,22 @@ config MDIO_REALTEK_RTL9300
> config MDIO_REGMAP
> tristate
> help
> - This driver allows using MDIO devices that are not sitting on a
> - regular MDIO bus, but still exposes the standard 802.3 register
> + This support module allows using MDIO devices that are not sitting on
> + a regular MDIO bus, but still exposes the standard 802.3 register
> layout. It's regmap-based so that it can be used on integrated,
> memory-mapped PHYs, SPI PHYs and so on. A new virtual MDIO bus is
> created, and its read/write operations are mapped to the underlying
> - regmap. Users willing to use this driver must explicitly select
> + regmap. Users willing to use this module must explicitly select
> REGMAP.

Thans for fixing these mistakes

>
> +config MDIO_REGMAP_SIMPLE
> + tristate
> + help
> + Generic platform driver for MDIO buses with a linear address space
> + that can be directly accessed using the MDIO_REGMAP support code and
> + need no special handling. The regmap is provided by the parent
> + device.
> +

It would probably make sense to add "select MDIO_REGMAP" here

> config MDIO_THUNDER
> tristate "ThunderX SOCs MDIO buses"
> depends on 64BIT
> diff --git a/drivers/net/mdio/Makefile b/drivers/net/mdio/Makefile
> index 9abf20d1b030..95f201b73a7d 100644
> --- a/drivers/net/mdio/Makefile
> +++ b/drivers/net/mdio/Makefile
> @@ -22,6 +22,7 @@ obj-$(CONFIG_MDIO_MVUSB) += mdio-mvusb.o
> obj-$(CONFIG_MDIO_OCTEON) += mdio-octeon.o
> obj-$(CONFIG_MDIO_REALTEK_RTL9300) += mdio-realtek-rtl9300.o
> obj-$(CONFIG_MDIO_REGMAP) += mdio-regmap.o
> +obj-$(CONFIG_MDIO_REGMAP_SIMPLE) += mdio-regmap-simple.o
> obj-$(CONFIG_MDIO_SJA1110_CBT1) += mdio-sja1110-cbt1.o
> obj-$(CONFIG_MDIO_SUN4I) += mdio-sun4i.o
> obj-$(CONFIG_MDIO_THUNDER) += mdio-thunder.o
> diff --git a/drivers/net/mdio/mdio-regmap-simple.c b/drivers/net/mdio/mdio-regmap-simple.c
> new file mode 100644
> index 000000000000..6ac390ec759b
> --- /dev/null
> +++ b/drivers/net/mdio/mdio-regmap-simple.c
> @@ -0,0 +1,77 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright 2025 NXP
> + *
> + * Generic MDIO bus driver for simple regmap-based MDIO devices
> + *
> + * This driver creates MDIO buses for devices that expose their internal
> + * PHYs or PCS through a regmap interface. It's intended to be a simple,
> + * generic driver similar to simple-mfd-i2c.c.
> + */
> +#include <linux/module.h>
> +#include <linux/of_mdio.h>
> +#include <linux/phy.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/mdio/mdio-regmap.h>
> +
> +struct mdio_regmap_simple_data {
> + u8 valid_addr;
> + bool autoscan;
> +};
> +
> +static const struct mdio_regmap_simple_data nxp_sja1110_base_tx = {
> + .valid_addr = 0,
> + .autoscan = false,
> +};
> +
> +static int mdio_regmap_simple_probe(struct platform_device *pdev)
> +{
> + const struct mdio_regmap_simple_data *data;
> + struct mdio_regmap_config config = {};
> + struct device *dev = &pdev->dev;
> + struct regmap *regmap;
> + struct mii_bus *bus;
> +
> + if (!dev->of_node || !dev->parent)
> + return -ENODEV;
> +
> + regmap = dev_get_regmap(dev->parent, NULL);
> + if (!regmap)
> + return -ENODEV;
> +
> + data = device_get_match_data(dev);
> +
> + config.regmap = regmap;
> + config.parent = dev;
> + config.name = dev_name(dev);
> + config.resource = platform_get_resource(pdev, IORESOURCE_REG, 0);

Just to clarify, a small comment to say that it's OK of
platform_get_resource() returns NULL maybe ?

> + if (data) {
> + config.valid_addr = data->valid_addr;
> + config.autoscan = data->autoscan;
> + }
> +
> + return PTR_ERR_OR_ZERO(devm_mdio_regmap_register(dev, &config));
> +}
> +
> +static const struct of_device_id mdio_regmap_simple_match[] = {
> + {
> + .compatible = "nxp,sja1110-base-tx-mdio",
> + .data = &nxp_sja1110_base_tx,
> + },
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, mdio_regmap_simple_match);
> +
> +static struct platform_driver mdio_regmap_simple_driver = {
> + .probe = mdio_regmap_simple_probe,
> + .driver = {
> + .name = "mdio-regmap-simple",
> + .of_match_table = mdio_regmap_simple_match,
> + },
> +};
> +
> +module_platform_driver(mdio_regmap_simple_driver);
> +
> +MODULE_DESCRIPTION("Generic MDIO bus driver for simple regmap-based devices");
> +MODULE_AUTHOR("Vladimir Oltean <vladimir.oltean@nxp.com>");
> +MODULE_LICENSE("GPL");

Thanks for this,

Maxime