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>
---
v1->v2:
- reorder MAINTAINERS entry to be alphabetic
- clarify that platform_get_resource() is optional (thanks to Maxime)
- update copyright to 2026
MAINTAINERS | 1 +
drivers/net/mdio/Kconfig | 15 ++++-
drivers/net/mdio/Makefile | 1 +
drivers/net/mdio/mdio-regmap-simple.c | 80 +++++++++++++++++++++++++++
4 files changed, 94 insertions(+), 3 deletions(-)
create mode 100644 drivers/net/mdio/mdio-regmap-simple.c
diff --git a/MAINTAINERS b/MAINTAINERS
index d3fec699c577..2b910fdd1122 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15671,6 +15671,7 @@ MDIO REGMAP DRIVER
M: Maxime Chevallier <maxime.chevallier@bootlin.com>
L: netdev@vger.kernel.org
S: Maintained
+F: drivers/net/mdio/mdio-regmap-simple.c
F: drivers/net/mdio/mdio-regmap.c
F: include/linux/mdio/mdio-regmap.h
diff --git a/drivers/net/mdio/Kconfig b/drivers/net/mdio/Kconfig
index 9819d1dc18de..c6e824baf228 100644
--- a/drivers/net/mdio/Kconfig
+++ b/drivers/net/mdio/Kconfig
@@ -179,14 +179,23 @@ 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.
+config MDIO_REGMAP_SIMPLE
+ tristate
+ select MDIO_REGMAP
+ 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.
+
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..5db1ca50c374
--- /dev/null
+++ b/drivers/net/mdio/mdio-regmap-simple.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright 2025-2026 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);
+ /* The resource is optional, provided for finding the registers
+ * within a device-wide non-MMIO regmap
+ */
+ config.resource = platform_get_resource(pdev, IORESOURCE_REG, 0);
+ 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");
--
2.34.1On Thu, Jan 22, 2026 at 12:56:42PM +0200, 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.
...
> +#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>
...
> +static const struct mdio_regmap_simple_data nxp_sja1110_base_tx = {
> + .valid_addr = 0,
> + .autoscan = false,
> +};
Actually the { } is enough to initialise that. But if you want to be super
explicit... :-)
...
> +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)
dev->of_node check is not needed, see below.
> + 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);
> + /* The resource is optional, provided for finding the registers
> + * within a device-wide non-MMIO regmap
> + */
> + config.resource = platform_get_resource(pdev, IORESOURCE_REG, 0);
> + if (data) {
We may always require data to be present. As you use a default one anyway.
> + config.valid_addr = data->valid_addr;
> + config.autoscan = data->autoscan;
> + }
And if it is not provided we will have a crash which is fine. It will just
point that the code was not ever been run on real HW.
> + return PTR_ERR_OR_ZERO(devm_mdio_regmap_register(dev, &config));
> +}
...
> +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,
> + },
> +};
> +
Unneeded blank line.
> +module_platform_driver(mdio_regmap_simple_driver);
--
With Best Regards,
Andy Shevchenko
On Thu, Jan 22, 2026 at 02:20:22PM +0200, Andy Shevchenko wrote:
> On Thu, Jan 22, 2026 at 12:56:42PM +0200, 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.
>
> ...
>
> > +#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>
>
> ...
>
> > +static const struct mdio_regmap_simple_data nxp_sja1110_base_tx = {
> > + .valid_addr = 0,
> > + .autoscan = false,
> > +};
>
> Actually the { } is enough to initialise that. But if you want to be super
> explicit... :-)
> ...
Yes, I guess I do.
> > +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)
>
> dev->of_node check is not needed, see below.
Oh.... this is a bug. dev->of_node should have been propagated to
devm_mdio_regmap_register() -> devm_mdiobus_register(), turning it into
devm_of_mdiobus_register().
It shows that my SJA1110 testing platform (Bluebox 3) doesn't have the
CBTX PHY routed to pinout, since I didn't catch this... I'll fix this
for v3.
> > + 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);
> > + /* The resource is optional, provided for finding the registers
> > + * within a device-wide non-MMIO regmap
> > + */
> > + config.resource = platform_get_resource(pdev, IORESOURCE_REG, 0);
>
> > + if (data) {
>
> We may always require data to be present. As you use a default one anyway.
>
> > + config.valid_addr = data->valid_addr;
> > + config.autoscan = data->autoscan;
> > + }
>
> And if it is not provided we will have a crash which is fine. It will just
> point that the code was not ever been run on real HW.
Hmm. This patch is super old, so I'm revisiting it with foreign eyes,
same as you.
I think the case with .valid_addr = 0 and .autoscan = false will
constitute the vast majority of instantiations of this driver.
I would like to avoid the proliferation of the same basic config with
100 different names (nxp_sja1110_base_tx, etc).
So for v3 I'm planning to:
- rename nxp_sja1110_base_tx to mdio_regmap_simple_default_data
- delete the "if (data)" conditional and directly assign from
device_get_match_data() to the config structure
Thanks for taking a look.
> > + return PTR_ERR_OR_ZERO(devm_mdio_regmap_register(dev, &config));
> > +}
>
> ...
>
> > +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,
> > + },
> > +};
>
> > +
>
> Unneeded blank line.
Ok.
> > +module_platform_driver(mdio_regmap_simple_driver);
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
On Thu, Jan 22, 2026 at 03:31:23PM +0200, Vladimir Oltean wrote:
> On Thu, Jan 22, 2026 at 02:20:22PM +0200, Andy Shevchenko wrote:
> > On Thu, Jan 22, 2026 at 12:56:42PM +0200, Vladimir Oltean wrote:
...
> > > +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)
> >
> > dev->of_node check is not needed, see below.
>
> Oh.... this is a bug. dev->of_node should have been propagated to
> devm_mdio_regmap_register() -> devm_mdiobus_register(), turning it into
> devm_of_mdiobus_register().
>
> It shows that my SJA1110 testing platform (Bluebox 3) doesn't have the
> CBTX PHY routed to pinout, since I didn't catch this... I'll fix this
> for v3.
Same Q, why not using fwnode APIs to begin with?
> > > + 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);
> > > + /* The resource is optional, provided for finding the registers
> > > + * within a device-wide non-MMIO regmap
> > > + */
> > > + config.resource = platform_get_resource(pdev, IORESOURCE_REG, 0);
> >
> > > + if (data) {
> >
> > We may always require data to be present. As you use a default one anyway.
> >
> > > + config.valid_addr = data->valid_addr;
> > > + config.autoscan = data->autoscan;
> > > + }
> >
> > And if it is not provided we will have a crash which is fine. It will just
> > point that the code was not ever been run on real HW.
>
> Hmm. This patch is super old, so I'm revisiting it with foreign eyes,
> same as you.
>
> I think the case with .valid_addr = 0 and .autoscan = false will
> constitute the vast majority of instantiations of this driver.
> I would like to avoid the proliferation of the same basic config with
> 100 different names (nxp_sja1110_base_tx, etc).
But you name it as default_blablalbla. That will be just assigned to each
currently "NULL" driver_data. We have examples in the kernel that do this.
IIRC 8250_dw cases, stmmac driver (PCI glue part of it?), et cetera...
> So for v3 I'm planning to:
> - rename nxp_sja1110_base_tx to mdio_regmap_simple_default_data
> - delete the "if (data)" conditional and directly assign from
> device_get_match_data() to the config structure
>
> Thanks for taking a look.
You're welcome!
> > > + return PTR_ERR_OR_ZERO(devm_mdio_regmap_register(dev, &config));
> > > +}
--
With Best Regards,
Andy Shevchenko
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